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Hi Monero community!

Two months ago I posted a CCS for continuing my research on Monero Atomic Swaps. That research is now complete and I'm happy to present my results.

This post will be a summary of my research, but you can also find the whitepaper that describes the full protocol and all the details here.

## Shiny BTC/XMR Atomic Swap Protocol!

**We found it!** With the help of the MRL, my colleagues, and the community, we created the first (to our knowledge) protocol to atomically swap bitcoin and monero. And this resulting protocol is implementable today - no more obscure crypto!

### Why now? What changed?

When I started studying Monero for a Bitcoin/Monero atomic swap three and a half years ago, most of the swap protocols where based on 'Hash Time Locked Contract' (HTLC), something that we all know as non-existent on Monero. So the goal at the beginning of the project was to create an atomic swap where all the logic (timeouts, possible sequences of operation, secret disclosures, etc) is managed on the other chain: the Bitcoin chain.

The second difficulty with Monero and Bitcoin is their respective underlying cryptographic parameters: they don't share the same elliptic curve, they don't share the same signing algorithm; they have nothing in common! This makes the pair a bad candidate for other types of atomic swap that don't (solely) rely on HTLC.

In November 2018 we came up with a draft protocol that respects the above constraints. Thus, the protocol requires a specific type of zero-knowledge proof to be trustless: a hash pre-image zero-knowledge proof. This type of zkp is not wildly used in practice, if at all. Thus the protocol works in theory, but with some obscure crypto, making the protocol a bad candidate for an implementation.

In early 2020, after presenting the draft protocol at 36C3 in December 2019, I discovered, by reference from Sarang Noether (MRL), Andrew Poelstra's idea of doing a*discrete logarithm equality across group zero-knowledge proof of knowledge* (MRL-0010), meaning that we can prove some relations between elements in two different groups (two curves to simplify) and the paper by LLoyd Fournier on One-Time Verifiably Encrypted Signatures allowing secret disclosure with ECDSA.

With these two new (to me) cryptographic primitives, we were able to replace the previous zero-knowledge proof with a combination of the latter, making the protocol complete and practically feasible.

### How it works

As a broad overview (and simplified) the protocol work as follow:

### Next steps

The obvious next step would be to have a working implementation on mainnet, but a ready-to-use implementation that is also robust and safe-to-use requires a lot of engineering work. Furthermore, even though the cryptography is not too obscure, most of it still also lacks an implementation.

I'll post soon, if the community wants it, a CCS proposal to get my team and I to work on implementing this protocol, step by step, with the end goal of creating a working client/daemon for swapping Bitcoin and Monero. It would be very exciting to build that!

### Conclusion

Thanks to the MRL and its researchers for their help, the CCS team, and the community for its support!

I hope I fulfilled the community's expectations for my my first CCS - all feedback is appreciated.

submitted by h4sh3d to Monero [link] [comments]
Two months ago I posted a CCS for continuing my research on Monero Atomic Swaps. That research is now complete and I'm happy to present my results.

This post will be a summary of my research, but you can also find the whitepaper that describes the full protocol and all the details here.

The second difficulty with Monero and Bitcoin is their respective underlying cryptographic parameters: they don't share the same elliptic curve, they don't share the same signing algorithm; they have nothing in common! This makes the pair a bad candidate for other types of atomic swap that don't (solely) rely on HTLC.

In November 2018 we came up with a draft protocol that respects the above constraints. Thus, the protocol requires a specific type of zero-knowledge proof to be trustless: a hash pre-image zero-knowledge proof. This type of zkp is not wildly used in practice, if at all. Thus the protocol works in theory, but with some obscure crypto, making the protocol a bad candidate for an implementation.

In early 2020, after presenting the draft protocol at 36C3 in December 2019, I discovered, by reference from Sarang Noether (MRL), Andrew Poelstra's idea of doing a

With these two new (to me) cryptographic primitives, we were able to replace the previous zero-knowledge proof with a combination of the latter, making the protocol complete and practically feasible.

- The monero are locked in an address generated by both participants
- At the beginning, neither of the participants have the full control over the address; they both have half of the private key only
- With the cross group discrete logarithm equality zkp, both participants prove to each other that the address on the Bitcoin chain is related to the address on the Monero chain
- By means of Bitcoin scripts and ECDSA one-time verifiably encrypted signatures, one participant reveals to the other her partial private key by taking the bitcoin, allowing the other to take control over the monero

I'll post soon, if the community wants it, a CCS proposal to get my team and I to work on implementing this protocol, step by step, with the end goal of creating a working client/daemon for swapping Bitcoin and Monero. It would be very exciting to build that!

I hope I fulfilled the community's expectations for my my first CCS - all feedback is appreciated.

Permissionless = RenVM is an open protocol; meaning anyone can use RenVM and any project can build with RenVM. You don't need anyone's permission, just plug RenVM into your dApp and you have interoperability.

Decentralized = The nodes that power RenVM ( Darknodes) are scattered throughout the world. RenVM has a peak capacity of up to 10,000 Darknodes (due to REN’s token economics). Realistically, there will probably be 100 - 500 Darknodes run in the initial Mainnet phases, ample decentralized nonetheless.

Permissionless = https://github.com/renproject/ren-js

Decentralized = https://chaosnet.renproject.io/

SSS by itself is just a way of representing secret data (like numbers). sMPC is how to generate and work with that data (like equations). One of the things you can do with that work is produce a form of TSS (this is what RenVM does).

However, TSS is slightly different because it can also be done *without* SSS and sMPC. For example, BLS signatures don’t use SSS or sMPC but they are still a form of TSS.

So, we say that RenVM uses SSS+sMPC because this is more specific than just saying TSS (and you can also do more with SSS+sMPC than just TSS). Specifically, all viable forms of turning ECDSA (a scheme that isn’t naturally threshold based) into a TSS needs SSS+sMPC.

People often get confused about RenVM and claim “SSS can’t be used to sign transactions without making the private key whole again”. That’s a strange statement and shows a fundamental misunderstanding about what SSS is.

To come back to our analogy, it’s like saying “numbers can’t be used to write a book”. That’s kind of true in a direct sense, but there are plenty of ways to encode a book as numbers and then it’s up to how you interpret (how you *use*) those numbers. This is exactly how this text I’m writing is appearing on your screen right now.

SSS is just secret data. It doesn’t make sense to say that SSS *functions*. RenVM is what does the functioning. RenVM *uses* the SSSs to represent private keys. But these are generated and used and destroyed as part of sMPC. The keys are never whole at any point.

tBTC an only mint/burn lots of 1 BTC and requires an on-Ethereum SPV relay for Bitcoin headers (and for any other chain it adds). No real advantage trade-off IMO.

tBTC has a liquidation mechanism that means nodes can have their bond liquidated because of ETH/BTC price ratio. Advantage means users can get 1 BTC worth of ETH. Disadvantage is it means tBTC is kind of a synthetic: needs a price feed, needs liquid markets for liquidation, users must accept exposure to ETH even if they only hold tBTC, nodes must stay collateralized or lose lots of ETH. RenVM doesn’t have this, and instead uses fees to prevent becoming under-collateralized. This requires a mature market, and assumed Darknodes will value their REN bonds fairly (based on revenue, not necessarily what they can sell it for at current —potentially manipulated—market value). That can be an advantage or disadvantage depending on how you feel.

tBTC focuses more on the idea of a tokenized version of BTC that feels like an ERC20 to the user (and is). RenVM focuses more on letting the user interact with DeFi and use real BTC and real Bitcoin transactions to do so (still an ERC20 under the hood, but the UX is more fluid and integrated). Advantage of tBTC is that it’s probably easier to understand and that might mean better overall experience, disadvantage really comes back to that 1 BTC limit and the need for a more clunky minting/burning experience that might mean worse overall experience. Too early to tell, different projects taking different bets.

tBTC supports BTC (I think they have ZEC these days too). RenVM supports BTC, BCH, and ZEC (docs discuss Matic, XRP, and LTC).

-Both are vulnerable to oracle attacks

-REN federation failure results in loss or theft of all funds

-tBTC failures tend to result in frothy markets, but holders of tBTC are made whole

-REN quorum rotation is new crypto, and relies on honest deletion of old key shares

-tBTC rotates micro-quorums regularly without relying on honest deletion

-tBTC relies on an SPV relay

-REN relies on federation honesty to fill the relay's purpose

-Both are brittle to deep reorgs, so expanding to weaker chains like ZEC is not clearly a good idea

-REN may see total system failure as the result of a deep reorg, as it changes federation incentives significantly

-tBTC may accidentally punish some honest micro-federations as the result of a deep reorg

-REN generally has much more interaction between incentive models, as everything is mixed into the same pot.

-tBTC is a large collection of small incentive models, while REN is a single complex incentive model

The oracle situation is different with RenVM, because the fee model is what determines the value of REN with respect to the cross-chain asset. This is the asset is what is used to pay the fee, so no external pricing is needed for it (because you only care about the ratio between REN and the cross-chain asset).

RenVM does rotate quorums regularly, in fact more regularly than in tBTC (although there are micro-quorums, each deposit doesn’t get rotated as far as I know and sticks around for up to 6 months). This rotation involves rotations of the keys too, so it does not rely on honest deletion of key shares.

Federated views of blockchains are easier to expand to support deep re-orgs (just get the nodes to wait for more blocks for that chain). SPV requires longer proofs which begins to scale more poorly.

Not sure what you mean by “one big pot”, but there are multiple quorums so the failure of one is isolated from the failures of others. For example, if there are 10 shards supporting BTC and one of them fails, then this is equivalent to a sudden 10% fee being applied. Harsh, yes, but not total failure of the whole system (and doesn’t affect other assets).

Would be interesting what RenVM would look like with lots more shards that are smaller. Failure becomes much more isolated and affects the overall network less.

Further, the amount of tBTC you can mint is dependent on people who are long ETH and prefer locking it up in Keep for earning a smallish fee instead of putting it in Compound or leveraging with dydx. tBTC is competing for liquidity while RenVM isn't.

A major advantage of Ren's specific usage of sMPC is that security can be regulated economically. All value (that's being interopped at least) passing through RenVM has explicit value. The network can self-regulate to ensure an attack is never worth it.

Profits of the Darknodes, and therefore security of the network, is based solely on the use of the network (this is what you want because your network does not make or break on things outside the systems control). In a system like tBTC there are liquidity issues because you need to convince ETH holders to bond ETH and this is an external problem. Maybe ETH is pumping irrespective of tBTC use and people begin leaving tBTC to sell their ETH. Or, that ETH is dumping, and so tBTC nodes are either liquidated or all their profits are eaten by the fact that they have to be long on ETH (and tBTC holders cannot get their BTC back in this case). Feels real bad man.

This cannot affect safety, because the first signature is still required. Any attack you wanted to do would still have to succeed against the “normal” part of the network. This can affect liveliness, because the semi-core could decide not to sign. However, the semi-core follows the same rules as normal shards. The signature is tolerant to 1/3rd for both safety/liveliness. So, 1/3rd+ would have to decide to not sign.

Members of the semi-core would be there under governance from the rest of our ecosystem. The idea is that members would be chosen for their external value. We’ve discussed in-depth the idea of L<3. But, if RenVM is used in MakerDAO, Compound, dYdX, Kyber, etc. it would be desirable to capture the value of these ecosystems too, not just the value of REN bonded. The semi-core as a second signature is a way to do this.

Imagine if the members for those projects, because those projects want to help secure renBTC, because it’s used in their ecosystems. There is a very strong incentive for them to behave honestly. To attack RenVM you first have to attack the Darknodes “as per usual” (the current design), and then somehow convince 1/3rd of these projects to act dishonestly and collapse their own ecosystems and their own reputations. This is a very difficult thing to do.

Worth reminding: the draft for this proposal isn’t finished. It would be great for everyone to give us their thoughts on GitHub when it is proposed, so we can keep a persistent record.

RenVM can be used to interoperate many different kinds of chains (anything using ECDSA, or naturally supporting lively threshold signatures) is a candidate to be included in RenVM. However, a centralised currency that has been bridged to a decentralised chain is not decentralised. The centralised entity that controls the currency might say “nothing transferred to/from this other chain will be honoured”. That’s a risk that you take with centralised currencies (take a look at the T&Cs for USDC for example).

The benefit of RenVM in these instances is to become a standard. Short-term, RenVM brings interoperability to some core chains. Medium-term, it expands that to other more interesting chains based on community demands. Long-term, it becomes the standard for how to implement interop. For example: you create a new chain and don’t worry about interop explicitly because you know RenVM will have your back. For centralised currencies this is still advantageous, because the issuing entity only has to manage one chain (theirs) but can still get their currency onto other chains/ecosystems.

From a technical perspective, the Darknodes just have to be willing to adopt the chain/currency.

Having time to fix the bug means that Darknodes may as well stick around and continue securing the network as best they can. Because their REN is at stake (as you put it) they’re incentivised to take any of the recommended actions and update their nodes as necessary.

This is also why it’s critical for the Greycore to exist in the early days of the network and why we are rolling out SubZero the way that we are. If such a bug becomes apparent (more likely in the early days than the later days), then the Greycore has a chance to react to it (the specifics of which would of course depend on the specifics of the bug). This becomes harder and slower as the network becomes more decentralised over time.

Not mcap, but the price of bonded Ren. Furthermore, the price will be determined by how much fees darknodes have collected. BTW, loongy could you unveil based on what profits ratio/apr the price will be calculated?

This is up to the Darknodes to governance softly. This means there isn’t a need for an explicit oracle. Darknodes assess L vs R individually and vote to increase fees to drive L down and drive R up. L is driven down by continue fees, whereas R is driven up by minting/burning fees.

Let X be the amount of REN used to voted, backed behind a Darknode and bonded for T time.

Let Y be the amount of time a Darknode has been active for.

Voting power of the Darknode could = Sqrt(Y) * Log(X + T)

Log(1,000,000,000) = ~21 so if you had every REN bonded behind you, your voting power would only be 21x the voting power of other nodes. This would force whales to either run Darknodes for a while and contribute actively to the ecosystem (or lock up their REN for an extended period for addition voting power), and would force exchanges to spread their voting out over many different nodes (giving power back to those running nodes). Obviously the exchange could just run lots of Darknodes, but they would have to do this over a long period of time (not feasible, because people need to be able to withdraw their REN).

Cryptology ePrint Archive: Report 2019/034

**Date:** 2019-01-14

**Author(s):** *Myrto Arapinis, Andriana Gkaniatsou, Dimitris Karakostas, Aggelos Kiayias*

# Link to Paper

**Abstract**

Bitcoin, being the most successful cryptocurrency, has been repeatedly attacked with many users losing their funds. The industry's response to securing the user's assets is to offer tamper-resistant hardware wallets. Although such wallets are considered to be the most secure means for managing an account, no formal attempt has been previously done to identify, model and formally verify their properties. This paper provides the first formal model of the Bitcoin hardware wallet operations. We identify the properties and security parameters of a Bitcoin wallet and formally define them in the Universal Composition (UC) Framework. We present a modular treatment of a hardware wallet ecosystem, by realizing the wallet functionality in a hybrid setting defined by a set of protocols. This approach allows us to capture in detail the wallet's components, their interaction and the potential threats. We deduce the wallet's security by proving that it is secure under common cryptographic assumptions, provided that there is no deviation in the protocol execution. Finally, we define the attacks that are successful under a protocol deviation, and analyze the security of commercially available wallets.

**References**

submitted by dj-gutz to myrXiv [link] [comments]
Bitcoin, being the most successful cryptocurrency, has been repeatedly attacked with many users losing their funds. The industry's response to securing the user's assets is to offer tamper-resistant hardware wallets. Although such wallets are considered to be the most secure means for managing an account, no formal attempt has been previously done to identify, model and formally verify their properties. This paper provides the first formal model of the Bitcoin hardware wallet operations. We identify the properties and security parameters of a Bitcoin wallet and formally define them in the Universal Composition (UC) Framework. We present a modular treatment of a hardware wallet ecosystem, by realizing the wallet functionality in a hybrid setting defined by a set of protocols. This approach allows us to capture in detail the wallet's components, their interaction and the potential threats. We deduce the wallet's security by proving that it is secure under common cryptographic assumptions, provided that there is no deviation in the protocol execution. Finally, we define the attacks that are successful under a protocol deviation, and analyze the security of commercially available wallets.

- KeepKey. https://keepkey.com/ (2018), [Online; accessed 1-Sep-2018]
- Ledger Receive Attack. https://www.docdroid.net/Jug5LX3/ledger-receive-address-attack.pdf (2018), [Online; accessed 19-Sep-2018]
- Trezor. https://trezor.io/ (2018), [Online; accessed 1-Sep-2018]
- Alois, J.: Ethereum parity hack may impact eth 500.000 or 146 million (2017)
- Atzei, N., Bartoletti, M., Lande, S., Zunino, R.: A formal model of bitcoin transactions. Financial Cryptography and Data Security. LNCS, Springer (2018)
- Badertscher, C., Maurer, U., Tschudi, D., Zikas, V.: Bitcoin as a transaction ledger: A composable treatment. pp. 324–356 (2017)
- Bamert, T., Decker, C., Wattenhofer, R., Welten, S.: Bluewallet: The secure bitcoin wallet. In: International Workshop on Security and Trust Management. pp. 65–80. Springer (2014)
- Bonneau, J., Miller, A., Clark, J., Narayanan, A., Kroll, J.A., Felten, E.W.: Sok: Research perspectives and challenges for bitcoin and cryptocurrencies. In: Security and Privacy (SP), 2015 IEEE Symposium on. pp. 104–121. IEEE (2015)
- Canetti, R.: Universally composable security: A new paradigm for cryptographic protocols. pp. 136–145 (2001)
- Canetti, R.: Universally composable signatures, certification and authentication. Cryptology ePrint Archive, Report 2003/239 (2003), http://eprint.iacr.org/2003/239
- Canetti, R., Krawczyk, H.: Universally composable notions of key exchange and secure channels. Cryptology ePrint Archive, Report 2002/059 (2002), http://eprint.iacr.org/2002/059
- Garay, J., Kiayias, A., Leonardos, N.: The bitcoin backbone protocol: Analysis and applications. In: Annual International Conference on the Theory and Applications of Cryptographic Techniques. pp. 281–310. Springer (2015)
- Gentilal, M., Martins, P., Sousa, L.: Trustzone-backed bitcoin wallet. In: Proceedings of the Fourth Workshop on Cryptography and Security in Computing Systems. pp. 25–28. ACM (2017)
- Gkaniatsou, A., Arapinis, M., Kiayias, A.: Low-level attacks in bitcoin wallets. In: International Conference on Information Security. pp. 233–253. Springer (2017)
- Heilman, E., Kendler, A., Zohar, A.: Eclipse attacks on bitcoin’s peer-to-peer network.
- Hsiao, H.C., Lin, Y.H., Studer, A., Studer, C., Wang, K.H., Kikuchi, H., Perrig, A., Sun, H.M., Yang, B.Y.: A study of user-friendly hash comparison schemes. In: Computer Security Applications Conference, 2009. ACSAC’09. Annual. pp. 105–114. IEEE (2009)
- Huang, D.Y., Dharmdasani, H., Meiklejohn, S., Dave, V., Grier, C., McCoy, D., Savage, S., Weaver, N., Snoeren, A.C., Levchenko, K.: Botcoin: Monetizing stolen cycles. In: NDSS. Citeseer (2014)
- Johnson, D., Menezes, A., Vanstone, S.: The elliptic curve digital signature algorithm (ecdsa). International journal of information security 1(1), 36–63 (2001)
- Lim, I.K., Kim, Y.H., Lee, J.G., Lee, J.P., Nam-Gung, H., Lee, J.K.: The analysis and countermeasures on security breach of bitcoin. In: International Conference on Computational Science and Its Applications. pp. 720–732. Springer (2014)
- Nakamoto, S.: Bitcoin: A peer-to-peer electronic cash system (2008)
- Parker, L.: Bitcoin stealing malware evolves again. https://bravenewcoin.com/news/bitcoin-stealing-malware-evolves-again/ (2016), [Online; accessed 1-Sep-2018]
- Pass, R., Seeman, L., Shelat, A.: Analysis of the blockchain protocol in asynchronous networks. In: Annual International Conference on the Theory and Applications of Cryptographic Techniques. pp. 643–673. Springer (2017)
- Penard, W., van Werkhoven, T.: On the secure hash algorithm family. Cryptography in Context pp. 1–18 (2008)
- Tan, J., Bauer, L., Bonneau, J., Cranor, L.F., Thomas, J., Ur, B.: Can unicorns help users compare crypto key fingerprints? In: Proceedings of the 2017 CHI Conference on Human Factors in Computing Systems. pp. 3787–3798. ACM (2017)
- Uzun, E., Karvonen, K., Asokan, N.: Usability analysis of secure pairing methods. In: International Conference on Financial Cryptography and Data Security. pp. 307–324. Springer (2007)
- Vasek, M., Bonneau, J., Ryan Castellucci, C.K., Moore, T.: The bitcoin brain drain: a short paper on the use and abuse of bitcoin brain wallets. Financial Cryptography and Data Security, Lecture Notes in Computer Science. Springer (2016)
- Volotikin, S.: Software attacks on hardware wallets. Black Hat USA 2018 (2018)
- Wuille, P.: Hierarchical Deterministic Wallets. https://en.bitcoin.it/wiki/BIP_0032 (2018), [Online; accessed 1-Sep-2018]

Hi guys, the other day I made a post requesting help understanding the transaction data of a bitcoin transaction. The data I was referring to is the json that is spit out by blockchain.info rawaddr data api call.

My initial objective was to simply create a function that would accept two parameters, FROM_WALLET_ADDRESS and TO_WALLET_ADDRESS and return all the bitcoin transactions that occurred between the two. I thought I could quickly do this without needing to understand exactly what was going on under the hood, however, with some help and direction to a wiki, I realized I better just read up on it, and educate myself about the transaction data.

As a show of gratitude for to the community and for the sake of sharing knowledge for the those who are might be as lazy as I am at times, here is what I've learned.

If I've understood something incorrectly, please do point it out, thank you!

Some cool related fact I came across as I was doing my research!

PS - /bitcoin Mods can you please unban gamedevelopersguild, he has demonstrated a clear desire to support and advance the cause of the bitcoin community and its members! Thank you!

submitted by Karmaa to Bitcoin [link] [comments]
My initial objective was to simply create a function that would accept two parameters, FROM_WALLET_ADDRESS and TO_WALLET_ADDRESS and return all the bitcoin transactions that occurred between the two. I thought I could quickly do this without needing to understand exactly what was going on under the hood, however, with some help and direction to a wiki, I realized I better just read up on it, and educate myself about the transaction data.

As a show of gratitude for to the community and for the sake of sharing knowledge for the those who are might be as lazy as I am at times, here is what I've learned.

If I've understood something incorrectly, please do point it out, thank you!

Some cool related fact I came across as I was doing my research!

- bitcoin addresses are derived hashing the public key using the ECDSA!
- Most hash values you see are Double Computed Hash - meaning the hash function is applied twice i.e. sha256(sha256('hello'))

**ver**: the version of the node making the outgoing connection, and identifying the protocol being used**inputs**: Records which reference the funds being transferred to this address from other previous transactions**relayed_by**: Whether or not a peer relayed transactions, see BIP 0037**out**: Records which determine the new owner of the transferred Bitcoins.**NOTE:**Under certain conditions, the amount of bitcoins sent, can sometimes exceed the sum intended, and it is returned in to the sender in the form of an outputs row.*This is one thing that confused me when I was trying to wing it and figure it out what the data was***lock_time**: Allows you to send bitcoins, yet lock them (prevent them from being spent) until a certain time is met .**result**: The total amount of bitcoins this transaction involved.**size**: No clue what this is - I'm going to take a WILD guess and say its the size of this transaction in bytes**time**: The linux time that the transaction took place**tx_index**:I believe this is the index id associated to this transaction?**vin_sz**: Number of inputs [inputs].**hash**: This is the Markel root, that uses all the related byte transactions associated to this particular transaction to generate the root hash value.**vout_sz**: Number of out [out].

PS - /bitcoin Mods can you please unban gamedevelopersguild, he has demonstrated a clear desire to support and advance the cause of the bitcoin community and its members! Thank you!

- Starting Algorithm: Keccak (SHA-3)
- Total coins: 250,000,000
- Block reward: 96 MaxCoin per block, halving every ~12 months with min reward of 1
- Difficulty: Retargeting using Kimoto Gravity Well algorithm
- Block time: 30 seconds

MaxCoin uses the Keccak (SHA-3) hashing algorithm for its Proof-of-Work. Keccak was selected as an alternative to the NSA designed SHA256 after a 5-year long competition held by the NIST and will be seen increasingly as the algorithm used in banking and other secure applications. A single round of Keccak is used, resulting in a 256 bit hash.

We have also implemented a provably-secure signing algorithm, EC-Schnorr. Every existing cryptocurrency uses the ECDSA algorithm, as chosen by Satoshi; whilst ECDSA is in common use and is secure, EC-Schnorr is

The cryptography choices within MaxCoin have been made to maximise security and, where possible, to minimise NSA influence. We have been advised throughout by the renowed cryptography expert Professor Nigel Smart (https://en.wikipedia.org/wiki/Nigel_Smart_(cryptographer)).

These changes also lay the foundation for some key features we're aiming to implement in MaxCoin over the coming months, so while they may currently appear uninteresting changes they pave the way for our future growth.

This is an issue of hardware miner resistance, such as ASICs. Keccak is the starting algorithm for MaxCoin and at this point in time no hardware miner currently exists. However, creating a Keccak ASIC is not impossible. Therefore, in order to protect against a hardware-miner future we are going to implement an "ASIC protection" feature into MaxCoin. This will work by allowing the blockchain to decide a new hashing algorithm for MaxCoin every x blocks. More specifically, the last authenticated transaction's hash is used to determine an integer and depending on this value an algorithm will be selected. This will mean hardware miners will find it difficult to create hardware in enough time to see profitable return. Purely for example, these could be:

x Algorithm 0 Keccak 1 Blake 2 Grostlx2 3 JH 4 Skein 5 Blake2 6 JH(Grostl) 7 Keccak+Blake

MaxCoin will have a zero % premine, proven by the timestamps of the first blocks in a block explorer, and we have attempted to combat low-difficulty instamining with a fast retarget rate up until block 200. At block 200 the Kimoto Gravity Well implementation will take over the retargeting.

Mining is done via CPU at release (mining guides about to be released also on this subreddit), but a GPU miner will not be far away. We've seen some versions in the works already after we released CPUminer yesterday, and while we have not yet seen a working version, this is very unlikely to take long. We'll update all official channels with Keccak GPU miner once it is available. It's also worth noting that any GPU miner created will not work after the first algorithm switch takes place.

https://preview.redd.it/50gpnoe1wdl11.jpg?width=900&format=pjpg&auto=webp&s=c636ddc4a1c49658cba067084009e557a113b8a8 submitted by intervalue to InterValue [link] [comments] InterValue aims to provide a global value Internet infrastructure. In response to deal with various problems that existing in the present blockchain infrastructure, InterValue optimizes the protocol and mechanism of blockchain technology at all levels, which can achieve the support agreement of value transmission network. At present, the InterValue 2.0 testnet has been released, we designed and implemented a new HashNet consensus mechanism. Transaction speed within one single shard exceeds 280,000 TPS and 4 million TPS for the whole network. Security (anti-quantum attack characteristics) is undoubtedly the highlight of InterValue under the goal of establishing a low-level infrastructure for the whole field of ecology. What is the quantum attack?Quantum computing is a new way of building computers—using the quantum properties of particles to perform operations on data, it is probably the same way as traditional computers. In some cases, the amount of algorithmic acceleration is unusual. It is this characteristics that makes some difficult problems that exist in the electronic computer environment become easy to calculate in the quantum computer. This superior computing power of quantum computers has influenced the security of existing public key cryptography which based on computational complexity. This is the quantum attack. What does anti-quantum attack mean?Algorithms have always been the underlying core of blockchain technology. Most of the current algorithms are unable to withstand quantum attacks. It means that all the information of the user will be exposed to the quantum computer. If you have an anti-quantum attack algorithm, it means that the personal information is safe, at least with current technology, it cannot be cracked. Anti-quantum attack algorithms mean security. The impact of quantum attacks on digital currencies is devastating. Quantum attacks directly disrupt existing information security systems. Quantum attacks will expose the assets in the digital industry, including the benefits of mining; the keys to your wallet will be cracked and the wallet will no longer be secure. Totally, the existing security system will be disintegrated. Therefore, it is imperative to develop anti-quantum attack algorithms in advance. It is a necessary technical means to firmly protect the privacy of users. InterValue uses a new anti-quantum attack cryptographic algorithm at the anti-quantum attack level. By replacing the ECDSA signature algorithm with the NTRUsign signature algorithm that based on the integer lattice, and replacing the existing SHA series algorithm with the Keccak-512 hash algorithm, the speed, and threats of the rapid quantum computation decrease. Adopt NTRUsign digital signature algorithmCurrent ECDSA signature algorithmThe current blockchain mainly uses the ECDSA digital signature algorithm based on elliptic curve. The signature algorithm: First, the public-private key pair needs to be generated, the private key user keeps it, the public key can be distributed to other people; secondly, the private key pair can be used and a specific message is signed; finally, the party that owns the signature public key is able to verify the signature. ECDSA has the advantages of small system parameters, fast processing speed, small key size, strong anti-attack and low bandwidth requirements. However, the quantum computer can implement a very efficient SHOR attack algorithm by ECDSA signature algorithm, and the ECDSA signature algorithm cannot resist the quantum attack. Adopt new NTRUsign-251 signature algorithmAt present, the public key cryptosystem against quantum SHOR algorithm attacks mainly includes public key cryptography that based on lattice theory, code-based public key system represented by McEliece public key cryptosystem and multivariate polynomial represented by MQ public key cryptography. The security of McEliece public key cryptosystem is based on the error correction code problem, which is strong in security but low in computational efficiency. The MQ public key cryptosystem, that is, the multivariate quadratic polynomial public key cryptosystem, based on the intractability of the multivariate quadratic polynomial equations on the finite field, has obvious disadvantages in terms of security. In contrast, the public key encryption system based on lattice theory is simple, fast, and takes up less storage space. InterValue uses the signature algorithm based on the lattice theory NTRUSign-251. The specific implementation process of the algorithm is as follows: https://preview.redd.it/byyzx8k3wdl11.png?width=762&format=png&auto=webp&s=d454123cabbe730271b66362a55e17b861ad50b4 It has been proved that the security of the NTRUSign-251 signature algorithm is ultimately equivalent to finding the shortest vector problem in a 502-dimensional integer lattice, but the SHOR attack algorithm for the shortest vector problem in the lattice is invalid, and there is no other fast solutions under the quantum computer. The best heuristic algorithm is also exponential, and the time complexity of attacking NTRUSign-251 signature algorithm is about 2168. Therefore, InterValue uses NTRUSign-251 algorithm that can resist SHOR algorithm attack under quantum computing. Adopt Keccak512 hash algorithmThe common anti-quantum hash algorithmThe most effective attack methods for hash algorithm under quantum computer is GROVER algorithm, which can reduce the attack complexity of Hash algorithm from O (2^n) to O (2^n/2). Therefore, the current bit adopts the Hash algorithm PIREMD160 whose output length is only 160 bits, under this circumstance, quantum attacks algorithm used in the currency system is not safe. An effective way of resisting quantum attacks is to reduce the threat of the GROVER algorithm by increasing the output length of the Hash algorithm. It is generally believed that the Hash algorithm can effectively resist quantum attacks as long as the output length of the hash algorithm is not less than 256 bits. In addition to the threat of quantum attacks, a series of hash functions that are widely used in practice, such as MD4, MD5, SHA-1, and HAVAL, are attacked by traditional methods such as differential analysis, modulo difference, and message modification methods. Therefore, blockchains’ Hash algorithm also needs to consider the resistance of traditional attacks. Winning the hash algorithm Keccak512Early blockchain projects such as Bitcoin, Litecoin, and Ethereum used SHA series Hashing algorithms that exist design flaws (but not fatal). Recently, new blockchain projects have been adopted by the National Institute of Standards and Technology. The SHA-3 plan series algorithm is a new Hash algorithm. InterValue adopts the SHA-3 plan's winning algorithm Keccak512, which contains many latest design concepts and ideas of hash function and cryptographic algorithm. It is simple in design, which is convenient for hardware implementation. The algorithm was submitted by Guido Bertoni, Joan Daemen, Michael Peters, and Giles Van Assche in October 2008. The Keccak512 algorithm uses a standard sponge structure that maps input bits of arbitrary length into fixed-length output bits. The speed is fast, with an average speed of 12.5 cycles per byte under the Intel Core 2 processor. https://preview.redd.it/z0nnrjp4wdl11.jpg?width=724&format=pjpg&auto=webp&s=bef29aafeb1ef74b21bacb6db3f07987bf0a7ba5 As shown in the figure, in the absorption phase of the sponge structure, each message packet is XORed with the r bits inside the state, and then encapsulated into 1600 bits of data together with the fixed c bits to perform the round function f processing, and then into the squeeze. In the extrusion phase, a hash of n-bit fixed output length can be generated by iterating 24 cycles. Each loop R has only the last step round constant, but the round constant is often ignored in collision attacks. The algorithm proved to have good differential properties, and until now third-party cryptanalysis did not show that Keccak512 has security weaknesses. The first type of original image attack complexity for the Keccak512 algorithm under quantum computer is 2^256, and the second type of original image attack complexity for the Keccak512 algorithm is 2^128, so InterValue combined with the Keccak512 algorithm can resist the GROVER algorithm attack under quantum computing. Written in the endQuantum computing has gone through 40 years from the theory to practice. From the emergence to the present, it has entered the stage of quantitative change to qualitative change in technology accumulation, business environment, and performance improvement. For the blockchain, the most deadly part is not investor's doubt, but the accelerated development of quantum computers. In the future, quantum computers are most likely to subvert the traditional technical route of classical computing and have a larger field of development. We are sympathetic to its destructive power to the existing blockchain, and we look forward to helping the entire blockchain industry to shape a new ecosystem. On the occasion of entering the new "quantum era, trusting society", the InterValue team believes that only by fully understanding the essence of quantum cryptography (quantum communication) and anti-quantum cryptography, can we calmly stand on a high level and arrange the outline. |

https://preview.redd.it/pl9ytli1smd11.jpg?width=900&format=pjpg&auto=webp&s=afd90001218bb19c252f927ef2e292cb788c9a9d submitted by intervalue to u/intervalue [link] [comments] InterValue aims to provide a global value Internet infrastructure. In response to deal with various problems that existing in the present blockchain infrastructure, InterValue optimizes the protocol and mechanism of blockchain technology at all levels, which can achieve the support agreement of value transmission network. At present, the InterValue 2.0 testnet has been released, we designed and implemented a new HashNet consensus mechanism. Transaction speed within one single shard exceeds 280,000 TPS and 4 million TPS for the whole network. Security (anti-quantum attack characteristics) is undoubtedly the highlight of InterValue under the goal of establishing a low-level infrastructure for the whole field of ecology. What is the quantum attack?Quantum computing is a new way of building computers—using the quantum properties of particles to perform operations on data, it is probably the same way as traditional computers. In some cases, the amount of algorithmic acceleration is unusual. It is this characteristics that makes some difficult problems that exist in the electronic computer environment become easy to calculate in the quantum computer. This superior computing power of quantum computers has influenced the security of existing public key cryptography which based on computational complexity. This is the quantum attack. What does anti-quantum attack mean?Algorithms have always been the underlying core of blockchain technology. Most of the current algorithms are unable to withstand quantum attacks. It means that all the information of the user will be exposed to the quantum computer. If you have an anti-quantum attack algorithm, it means that the personal information is safe, at least with current technology, it cannot be cracked. Anti-quantum attack algorithms mean security. The impact of quantum attacks on digital currencies is devastating. Quantum attacks directly disrupt existing information security systems. Quantum attacks will expose the assets in the digital industry, including the benefits of mining; the keys to your wallet will be cracked and the wallet will no longer be secure. Totally, the existing security system will be disintegrated. Therefore, it is imperative to develop anti-quantum attack algorithms in advance. It is a necessary technical means to firmly protect the privacy of users. InterValue uses a new anti-quantum attack cryptographic algorithm at the anti-quantum attack level. By replacing the ECDSA signature algorithm with the NTRUsign signature algorithm that based on the integer lattice, and replacing the existing SHA series algorithm with the Keccak-512 hash algorithm, the speed, and threats of the rapid quantum computation decrease. Adopt NTRUsign digital signature algorithmCurrent ECDSA signature algorithmThe current blockchain mainly uses the ECDSA digital signature algorithm based on elliptic curve. The signature algorithm: First, the public-private key pair needs to be generated, the private key user keeps it, the public key can be distributed to other people; secondly, the private key pair can be used and a specific message is signed; finally, the party that owns the signature public key is able to verify the signature. ECDSA has the advantages of small system parameters, fast processing speed, small key size, strong anti-attack and low bandwidth requirements. However, the quantum computer can implement a very efficient SHOR attack algorithm by ECDSA signature algorithm, and the ECDSA signature algorithm cannot resist the quantum attack. Adopt new NTRUsign-251 signature algorithmAt present, the public key cryptosystem against quantum SHOR algorithm attacks mainly includes public key cryptography that based on lattice theory, code-based public key system represented by McEliece public key cryptosystem and multivariate polynomial represented by MQ public key cryptography. The security of McEliece public key cryptosystem is based on the error correction code problem, which is strong in security but low in computational efficiency. The MQ public key cryptosystem, that is, the multivariate quadratic polynomial public key cryptosystem, based on the intractability of the multivariate quadratic polynomial equations on the finite field, has obvious disadvantages in terms of security. In contrast, the public key encryption system based on lattice theory is simple, fast, and takes up less storage space. InterValue uses the signature algorithm based on the lattice theory NTRUSign-251. The specific implementation process of the algorithm is as follows: https://preview.redd.it/uzuqi589smd11.png?width=762&format=png&auto=webp&s=29670c99027fdcebadca64730ef2e3862f960192 It has been proved that the security of the NTRUSign-251 signature algorithm is ultimately equivalent to finding the shortest vector problem in a 502-dimensional integer lattice, but the SHOR attack algorithm for the shortest vector problem in the lattice is invalid, and there is no other fast solutions under the quantum computer. The best heuristic algorithm is also exponential, and the time complexity of attacking NTRUSign-251 signature algorithm is about 2168. Therefore, InterValue uses NTRUSign-251 algorithm that can resist SHOR algorithm attack under quantum computing. Adopt Keccak512 hash algorithmThe common anti-quantum hash algorithmThe most effective attack methods for hash algorithm under quantum computer is GROVER algorithm, which can reduce the attack complexity of Hash algorithm from O (2^n) to O (2^n/2). Therefore, the current bit adopts the Hash algorithm PIREMD160 whose output length is only 160 bits, under this circumstance, quantum attacks algorithm used in the currency system is not safe. An effective way of resisting quantum attacks is to reduce the threat of the GROVER algorithm by increasing the output length of the Hash algorithm. It is generally believed that the Hash algorithm can effectively resist quantum attacks as long as the output length of the hash algorithm is not less than 256 bits. In addition to the threat of quantum attacks, a series of hash functions that are widely used in practice, such as MD4, MD5, SHA-1, and HAVAL, are attacked by traditional methods such as differential analysis, modulo difference, and message modification methods. Therefore, blockchains’ Hash algorithm also needs to consider the resistance of traditional attacks. Winning the hash algorithm Keccak512Early blockchain projects such as Bitcoin, Litecoin, and Ethereum used SHA series Hashing algorithms that exist design flaws (but not fatal). Recently, new blockchain projects have been adopted by the National Institute of Standards and Technology. The SHA-3 plan series algorithm is a new Hash algorithm. InterValue adopts the SHA-3 plan's winning algorithm Keccak512, which contains many latest design concepts and ideas of hash function and cryptographic algorithm. It is simple in design, which is convenient for hardware implementation. The algorithm was submitted by Guido Bertoni, Joan Daemen, Michael Peters, and Giles Van Assche in October 2008. The Keccak512 algorithm uses a standard sponge structure that maps input bits of arbitrary length into fixed-length output bits. The speed is fast, with an average speed of 12.5 cycles per byte under the Intel Core 2 processor. https://preview.redd.it/zwfzybeasmd11.jpg?width=724&format=pjpg&auto=webp&s=e0710e7fb1f80b7aa6517a296e2cadd6a51bd4c8 As shown in the figure, in the absorption phase of the sponge structure, each message packet is XORed with the r bits inside the state, and then encapsulated into 1600 bits of data together with the fixed c bits to perform the round function f processing, and then into the squeeze. In the extrusion phase, a hash of n-bit fixed output length can be generated by iterating 24 cycles. Each loop R has only the last step round constant, but the round constant is often ignored in collision attacks. The algorithm proved to have good differential properties, and until now third-party cryptanalysis did not show that Keccak512 has security weaknesses. The first type of original image attack complexity for the Keccak512 algorithm under quantum computer is 2^256, and the second type of original image attack complexity for the Keccak512 algorithm is 2^128, so InterValue combined with the Keccak512 algorithm can resist the GROVER algorithm attack under quantum computing. Written in the endQuantum computing has gone through 40 years from the theory to practice. From the emergence to the present, it has entered the stage of quantitative change to qualitative change in technology accumulation, business environment, and performance improvement. For the blockchain, the most deadly part is not investor's doubt, but the accelerated development of quantum computers. In the future, quantum computers are most likely to subvert the traditional technical route of classical computing and have a larger field of development. We are sympathetic to its destructive power to the existing blockchain, and we look forward to helping the entire blockchain industry to shape a new ecosystem. On the occasion of entering the new "quantum era, trusting society", the InterValue team believes that only by fully understanding the essence of quantum cryptography (quantum communication) and anti-quantum cryptography, can we calmly stand on a high level and arrange the outline. |

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1 Basic knowledge of cryptography 1.1 Basic knowledge of elliptic curves 1.1.1Elliptic curve profile Let denote a finite domain, an elliptic curve defined in it, actually this curve represented as a set of points, defines an operation on elliptic curve, and two points on the elliptic curve, a + = for the two point addition operation. The intersection of the line and the curve represented by the point, and the point on the elliptic curve of the symmetry. At this point, when = when, the intersection of the tangent and the curve is represented as the point on the axis of the elliptic curve. Thus, the Abel group is formed on the finite field (+ +), and the addition unit element is. 1.1.2 Signature algorithm Defines an elliptic curve called [()) and its base point, which is the order. For the curve @ (), make a public key pair, in which the private key is the public key and can be made public. Step1: first, using Hash function to calculate the plaintext message, the Hash function algorithm used MD5 algorithm or SHA-1 algorithm can calculate the plaintext message value = (Step2); then in the interval [1, and the private key a random integer as the signature of a range of 1]; Step3: calculation a public key =;Step4: = = K, where K is the abscissa of the public key and, if = 0, returns to Step2; Step5: = = Q/ (+), which is the private key of the sender A, and if = 0, returns to Step2; Step6: the sender A transmits the message signature (to) to the receiver B. The receiver receives the message signature (B,), the specific verification process to sign the message as follows: Step1: firstly, message signature and verification, i.e. whether it is in the interval [1, N1] positive integer range, if the signature does not comply with the signature of the message, that message signature received (,) is not a valid legal signature; Step2: according to the signature public key of the sender A, the sender A and the receiver B have the same Hash function digest value, and the digest value of the signed message is calculated (=); Step3: calculates the parameter value = Q/; Step4: calculates the parameter value = = Step5: calculates the parameter value = = Step6: calculates the parameter value = +; Step7: if = 0, the receiver B may deny the signature. Otherwise, calculate '= K', where K is the parameter A horizontal coordinate; a signature. The digital signature based on ECC, partly because this scheme can avoid the order operation in the inverse operation, so it is better than the signature scheme based on discrete logarithm algorithm should be simple; on the other hand it is because the calculation of the plaintext message () (,) than the calculation simple, so its speed Schnorr digital signature scheme is faster than. Therefore, the digital signature scheme based on elliptic curve cryptography has good application advantages in resisting attack security strength, key length, computation speed, computation cost and bandwidth requirement. 1.2 Threshold key sharing technology 1.2.1 Shamir Threshold key sharing concept Threshold key sharing technology solves the key security management problem. The design of modern cryptography system is that depends on the security of cryptosystem in the cryptographic key leakage means the lost security system, so the key management plays an important role in the research and design of security in cryptography. Especially when multiple stakeholders manage an account, the key of the account is trusted, and it is very difficult to distribute it safely to multi-party participants. To solve this problem, the Israeli cryptographer Shamir proposed Shamir (,) the concept of threshold secret sharing: the key is divided into portions assigned to participants, each participant to grasp a key share, only collect more than key share, can the key recovery. 1.2.2 Linear secret sharing mechanism Linear secret sharing is the generalization of Shamir threshold key sharing. Its essence is that both the primary key space, the sub key space and the random input set are linear spaces, and the key reconstruction function is linear. The formal definition is as follows: let be a finite domain, PI is a key access structure sharing system, is the main key space. We say that Pi is a linear key sharing system, if the following conditions are met: 1) sub key is linear space, namely for, constant B, the sub key space B cd. Remember - B, e (,) as the components of B CD vector space is received, this component is dependent on the primary key and the random number 2) each authorization set may obtain the master key by means of a linear combination of sub keys, that is, for any one delegate The right to set in, constant {b, e:, B, less than 1 and less than or equal to b}, such that for any master key and random number, All = KD and l /jejcd B, e, B (E, II). 1.2.3 Shamir Polynomial interpolation threshold secret sharing scheme Shamir combines the characteristics of polynomials over finite fields and the theory of Lagrange's reconstructed polynomial, designs a threshold key management scheme based on Lagrange interpolation polynomial, and the scheme is as follows 1.3 Secure multi-party computation 1.3.1 The background of secure multiparty computation With the rapid development of Internet, more and more applications require cooperative computing among network users. But because of privacy protection and data security considerations, the user does not want to participate in collaborative computing and other users to calculate data sharing, this problem leads to collaborative computing cannot be performed, which leads to efficient use and share some of the scenarios can not be difficult to achieve the cyber source. Secure multi-party computation (secure multi-party computation) makes this problem easy to solve, and it provides a theoretical basis for solving the contradiction between data privacy protection and collaborative computing. Secure multi-party computation is the theoretical foundation of distributed cryptography, and also a basic problem of distributed computing. Secure multi-party computation means that in a non trusted multi-user network, two or more users can cooperate with each other to execute a computing task without leaking their private input information. In brief, secure multi-party computation refers to a set of people, such as /...... Q, computing functions together safely,...... , q = (/),...... (Q). Where the input of this function is held by the participant secretly, the secret input of B is B, and after the calculation, B gets the output B. Here is the safety requirements of cheating participants even in some cases, to ensure the correctness of the calculated results, which is calculated after the end of each honest participant B can get the correct output of B, but also requires each participant to ensure confidentiality of input, namely each participant B (B, b) in addition. Don't get any other information. Secure multi-party computation has been rich in theoretical results and powerful tools. Although its practical application is still in its infancy, it will eventually become an indispensable part of computer security. 1.3.2 Classification of secure multiparty computation protocols At present, secure multi-party computation protocols can be divided into four categories according to the different implementations: L secure multi-party computation protocol based on VSS sub protocol Most of the existing secure multi-party computation protocols adopt verifiable key sharing VSS (Verifiable Secret) (Sharing) the sub protocol is the basis of protocol construction, which is suitable for computing functions on any finite field. The finite field of arbitrary function can be expressed as the domain definition of addition and multiplication of the directed graph, so long as can secure computing addition and multiplication, we can calculate each addition and multiplication to calculate any function over finite fields. L secure multi-party computation protocol based on Mix-Match The secure multi-party computation protocol based on VSS sub protocol can compute arbitrary functions, but it can not efficiently calculate Boolean functions. Therefore, another secure multi-party protocol called Mix-Match is proposed. The basic idea of this protocol is that participants use secret sharing schemes to share the system's private key, and the system's public key is open. During the protocol, the participants randomly encrypt their own input public key y, then publish their own encryption results, and finally make all participants gain common output through Mix-Match. L secure multi-party computation protocol based on OT OT based secure multi-party computation protocol for computing arbitrary bit functions. It implements with "OT sub Protocol" and (and), or (or) "," (not) "three basic operations, then the arbitrary bit operation function is decomposed into a combination of three basic operations, finally by using iterative method to calculate the bit operation function. L secure multi-party computation based on homomorphic encryption Homomorphic encryption, secure multi-party computation can resist active attacks based on it is the idea of the selected atom is calculated, the calculation can be decomposed into a sequence of atomic computing allows arbitrary function and atomic calculation of input and output using homomorphic encryption, to get the final results in the encrypted state, only a specific set of participants will be able to the calculation results decrypted plaintext. 1.4 Introduction to ring signature In 2001, Rivest et al proposed a new signature technique, called Ring Signature, in the context of how to reveal the secret anonymously. Ring signature can be regarded as a kind of special group signature (Group Signature), because the establishment process need the trusted center and security group signature, often there are loopholes in the protection of anonymous (signer is traceable to the trusted center), group signature and ring signature in the foundation process in addition to the establishment of a trusted center and security. For the verifier, the signer is completely anonymous, so ring signature is more practical. Since the self ring signature was proposed, a large number of scholars have discovered its important value, such as elliptic curve, threshold and other ring signatures Volume design and development can be divided into four categories: 1. threshold ring signature 2. associated ring signature 3. revocable anonymous ring signature 4. deniable ring signature for block chain contract intelligent token transactions privacy, we use a linkable ring signature, in order to achieve privacy and prevent double problem. 2 A secure account generation scheme based on secure multi-party computation and threshold key sharing 2.1 Basic operations of secure multi-party computation The addition and multiplication, inverse element into three basic operations on the finite field, any computation can be decomposed into a sequence of the finite field addition and multiplication, inverse element, so long as to complete the three basic operations of multi-party computation, so the calculation process can be arbitrary finite domains through multi-party computation the basic operation to iterate the agreement. In this paper, we introduce a secure multi-party computation algorithm for finite fields based on secret sharing scheme based on Lagrange interpolation polynomial. 2.1.1 Addition In the secret sharing scheme based on Lagrange interpolation polynomial, the need to identify a polynomial, a shared secret is the constant term of this polynomial, and the secret share was value of this polynomial at a certain point. It is possible to set and share two secrets, the corresponding polynomials are w and X, and the secret share of participant B is b = w, B = X. In order to get the secret share of secret +, the participant B needs to construct a polynomial so that the constant of the polynomial is +, and B can be calculated. The construction process is as follows: B and B share a secret dreams and secrets, and the corresponding polynomial for W and X L = w + W / +. + W, oQ/oQ/ = {x + / +, +. X, oQ/oQ/ Might as well define = w + x = = w + x = B + B It was - 1 polynomial, and the constant term is +, for this polynomial in value * b = as + secret secret share Secure multi-party computation algorithm obtained by adding the above construction process: Addition of multi-party computation algorithms: secret, secret share, B, B output: Secret + secret share B 1)B = B + B 2.1.2 multiplication Set up two secrets, the corresponding polynomials are w and X, and the secret share of participant B is b = w, B = X. If the participants directly in the local computing B and B share a secret product, although the calculation after sharing secret is the constant term polynomials, but the degree of the polynomial is 2 (- 1), so the need to reduce the number of polynomial. The W and X share the secret share of the participant B, and the product of W and X is: Wx = w = x + / +. + (oQ/), (oQ/) Wx x = w, 1 = 1 + 1 = 2. Represented by matrices: - 1 When the upper coefficient matrix is written, it is obviously a nonsingular matrix, and the inverse matrix is denoted as Q/, which is a constant Number matrix. Remember (/, - - -, oQ/) is the first line of the matrix Q/, there are: /wx = 1 + - + - - oQ/wx, 2 - 1 Each participant randomly selected 2 - 1 - 1 - - - / polynomial, and, oQ/, to meet the requirements of B 0 = wx. Definition = "B, oQ/ Obviously: OQ/. 0 = b b 0 = /wx 1 + - - - 2 - 1 = oQ/wx +. B OQ/. = b b B Therefore, the secret is to share the secret and share the secret. A multi-party computation algorithm for multiplication 2.1.3 yuan inverse Set the secret of sharing, the corresponding polynomial is w, and the secret share of participant B is b = W. One yuan Inversion is refers to the participants by B B secret share calculation Q/ w (c) a secret share, but in the process of calculation Can not disclose, Q/ and secret share of the two. The calculation is as follows: Participant B selects the random number B, and selects the random polynomial B () to compute its secret share be = B () to the participant E. To accept all the secret share, e n = Q. Thus all participants share the same random number David - +q + = / s.. Using the multiplicative multi-party computation algorithm, the secret obtained by the secret share is calculated Share w, and sent to the other participants, so it can be recovered by using the Lagrange interpolation, we may assume that = . It is clear that the W - a Q/ C = n, i.e. Q/'s Secret share. 2.2 lock account generation scenarios The lock account generation scheme is an improvement on threshold key management scheme based on Lagrange interpolation polynomial. Its basic idea is that through the threshold secret sharing, all the authentication nodes generate a lock account in a centralized way, and each verification node has a share of the lock private key. This ensures that the lock account private key is distributed in the entire network in the form of the private key share, so it can be centralized management. 2.3 lock account signature scheme The lock account signature algorithm uses the ECDSA signature algorithm, because it is the current block chain project's mainstream signature algorithm, this choice can improve the system compatibility. In a locked account signature generation process, different from the original ECDSA signature algorithm, the private key and the random number to account is in the form of multi-party computation involved in ECDSA signature process; lock account signature verification process with the original ECDSA signature verification algorithm. Therefore, only the lock account signature generation process is described

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Author: klcchain

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1 Basic knowledge of cryptography 1.1 Basic knowledge of elliptic curves 1.1.1Elliptic curve profile Let denote a finite domain, an elliptic curve defined in it, actually this curve represented as a set of points, defines an operation on elliptic curve, and two points on the elliptic curve, a + = for the two point addition operation. The intersection of the line and the curve represented by the point, and the point on the elliptic curve of the symmetry. At this point, when = when, the intersection of the tangent and the curve is represented as the point on the axis of the elliptic curve. Thus, the Abel group is formed on the finite field (+ +), and the addition unit element is. 1.1.2 Signature algorithm Defines an elliptic curve called [()) and its base point, which is the order. For the curve @ (), make a public key pair, in which the private key is the public key and can be made public. Step1: first, using Hash function to calculate the plaintext message, the Hash function algorithm used MD5 algorithm or SHA-1 algorithm can calculate the plaintext message value = (Step2); then in the interval [1, and the private key a random integer as the signature of a range of 1]; Step3: calculation a public key =;Step4: = = K, where K is the abscissa of the public key and, if = 0, returns to Step2; Step5: = = Q/ (+), which is the private key of the sender A, and if = 0, returns to Step2; Step6: the sender A transmits the message signature (to) to the receiver B. The receiver receives the message signature (B,), the specific verification process to sign the message as follows: Step1: firstly, message signature and verification, i.e. whether it is in the interval [1, N1] positive integer range, if the signature does not comply with the signature of the message, that message signature received (,) is not a valid legal signature; Step2: according to the signature public key of the sender A, the sender A and the receiver B have the same Hash function digest value, and the digest value of the signed message is calculated (=); Step3: calculates the parameter value = Q/; Step4: calculates the parameter value = = Step5: calculates the parameter value = = Step6: calculates the parameter value = +; Step7: if = 0, the receiver B may deny the signature. Otherwise, calculate '= K', where K is the parameter A horizontal coordinate; a signature. The digital signature based on ECC, partly because this scheme can avoid the order operation in the inverse operation, so it is better than the signature scheme based on discrete logarithm algorithm should be simple; on the other hand it is because the calculation of the plaintext message () (,) than the calculation simple, so its speed Schnorr digital signature scheme is faster than. Therefore, the digital signature scheme based on elliptic curve cryptography has good application advantages in resisting attack security strength, key length, computation speed, computation cost and bandwidth requirement. 1.2 Threshold key sharing technology 1.2.1 Shamir Threshold key sharing concept Threshold key sharing technology solves the key security management problem. The design of modern cryptography system is that depends on the security of cryptosystem in the cryptographic key leakage means the lost security system, so the key management plays an important role in the research and design of security in cryptography. Especially when multiple stakeholders manage an account, the key of the account is trusted, and it is very difficult to distribute it safely to multi-party participants. To solve this problem, the Israeli cryptographer Shamir proposed Shamir (,) the concept of threshold secret sharing: the key is divided into portions assigned to participants, each participant to grasp a key share, only collect more than key share, can the key recovery. 1.2.2 Linear secret sharing mechanism Linear secret sharing is the generalization of Shamir threshold key sharing. Its essence is that both the primary key space, the sub key space and the random input set are linear spaces, and the key reconstruction function is linear. The formal definition is as follows: let be a finite domain, PI is a key access structure sharing system, is the main key space. We say that Pi is a linear key sharing system, if the following conditions are met: 1) sub key is linear space, namely for, constant B, the sub key space B cd. Remember - B, e (,) as the components of B CD vector space is received, this component is dependent on the primary key and the random number 2) each authorization set may obtain the master key by means of a linear combination of sub keys, that is, for any one delegate The right to set in, constant {b, e:, B, less than 1 and less than or equal to b}, such that for any master key and random number, All = KD and l /jejcd B, e, B (E, II). 1.2.3 Shamir Polynomial interpolation threshold secret sharing scheme Shamir combines the characteristics of polynomials over finite fields and the theory of Lagrange's reconstructed polynomial, designs a threshold key management scheme based on Lagrange interpolation polynomial, and the scheme is as follows 1.3 Secure multi-party computation 1.3.1 The background of secure multiparty computation With the rapid development of Internet, more and more applications require cooperative computing among network users. But because of privacy protection and data security considerations, the user does not want to participate in collaborative computing and other users to calculate data sharing, this problem leads to collaborative computing cannot be performed, which leads to efficient use and share some of the scenarios can not be difficult to achieve the cyber source. Secure multi-party computation (secure multi-party computation) makes this problem easy to solve, and it provides a theoretical basis for solving the contradiction between data privacy protection and collaborative computing. Secure multi-party computation is the theoretical foundation of distributed cryptography, and also a basic problem of distributed computing. Secure multi-party computation means that in a non trusted multi-user network, two or more users can cooperate with each other to execute a computing task without leaking their private input information. In brief, secure multi-party computation refers to a set of people, such as /...... Q, computing functions together safely,...... , q = (/),...... (Q). Where the input of this function is held by the participant secretly, the secret input of B is B, and after the calculation, B gets the output B. Here is the safety requirements of cheating participants even in some cases, to ensure the correctness of the calculated results, which is calculated after the end of each honest participant B can get the correct output of B, but also requires each participant to ensure confidentiality of input, namely each participant B (B, b) in addition. Don't get any other information. Secure multi-party computation has been rich in theoretical results and powerful tools. Although its practical application is still in its infancy, it will eventually become an indispensable part of computer security. 1.3.2 Classification of secure multiparty computation protocols At present, secure multi-party computation protocols can be divided into four categories according to the different implementations: L secure multi-party computation protocol based on VSS sub protocol Most of the existing secure multi-party computation protocols adopt verifiable key sharing VSS (Verifiable Secret) (Sharing) the sub protocol is the basis of protocol construction, which is suitable for computing functions on any finite field. The finite field of arbitrary function can be expressed as the domain definition of addition and multiplication of the directed graph, so long as can secure computing addition and multiplication, we can calculate each addition and multiplication to calculate any function over finite fields. L secure multi-party computation protocol based on Mix-Match The secure multi-party computation protocol based on VSS sub protocol can compute arbitrary functions, but it can not efficiently calculate Boolean functions. Therefore, another secure multi-party protocol called Mix-Match is proposed. The basic idea of this protocol is that participants use secret sharing schemes to share the system's private key, and the system's public key is open. During the protocol, the participants randomly encrypt their own input public key y, then publish their own encryption results, and finally make all participants gain common output through Mix-Match. L secure multi-party computation protocol based on OT OT based secure multi-party computation protocol for computing arbitrary bit functions. It implements with "OT sub Protocol" and (and), or (or) "," (not) "three basic operations, then the arbitrary bit operation function is decomposed into a combination of three basic operations, finally by using iterative method to calculate the bit operation function. L secure multi-party computation based on homomorphic encryption Homomorphic encryption, secure multi-party computation can resist active attacks based on it is the idea of the selected atom is calculated, the calculation can be decomposed into a sequence of atomic computing allows arbitrary function and atomic calculation of input and output using homomorphic encryption, to get the final results in the encrypted state, only a specific set of participants will be able to the calculation results decrypted plaintext. 1.4 Introduction to ring signature In 2001, Rivest et al proposed a new signature technique, called Ring Signature, in the context of how to reveal the secret anonymously. Ring signature can be regarded as a kind of special group signature (Group Signature), because the establishment process need the trusted center and security group signature, often there are loopholes in the protection of anonymous (signer is traceable to the trusted center), group signature and ring signature in the foundation process in addition to the establishment of a trusted center and security. For the verifier, the signer is completely anonymous, so ring signature is more practical. Since the self ring signature was proposed, a large number of scholars have discovered its important value, such as elliptic curve, threshold and other ring signatures Volume design and development can be divided into four categories: 1. threshold ring signature 2. associated ring signature 3. revocable anonymous ring signature 4. deniable ring signature for block chain contract intelligent token transactions privacy, we use a linkable ring signature, in order to achieve privacy and prevent double problem. 2 A secure account generation scheme based on secure multi-party computation and threshold key sharing 2.1 Basic operations of secure multi-party computation The addition and multiplication, inverse element into three basic operations on the finite field, any computation can be decomposed into a sequence of the finite field addition and multiplication, inverse element, so long as to complete the three basic operations of multi-party computation, so the calculation process can be arbitrary finite domains through multi-party computation the basic operation to iterate the agreement. In this paper, we introduce a secure multi-party computation algorithm for finite fields based on secret sharing scheme based on Lagrange interpolation polynomial. 2.1.1 Addition In the secret sharing scheme based on Lagrange interpolation polynomial, the need to identify a polynomial, a shared secret is the constant term of this polynomial, and the secret share was value of this polynomial at a certain point. It is possible to set and share two secrets, the corresponding polynomials are w and X, and the secret share of participant B is b = w, B = X. In order to get the secret share of secret +, the participant B needs to construct a polynomial so that the constant of the polynomial is +, and B can be calculated. The construction process is as follows: B and B share a secret dreams and secrets, and the corresponding polynomial for W and X L = w + W / +. + W, oQ/oQ/ = {x + / +, +. X, oQ/oQ/ Might as well define = w + x = = w + x = B + B It was - 1 polynomial, and the constant term is +, for this polynomial in value * b = as + secret secret share Secure multi-party computation algorithm obtained by adding the above construction process: Addition of multi-party computation algorithms: secret, secret share, B, B output: Secret + secret share B 1)B = B + B 2.1.2 multiplication Set up two secrets, the corresponding polynomials are w and X, and the secret share of participant B is b = w, B = X. If the participants directly in the local computing B and B share a secret product, although the calculation after sharing secret is the constant term polynomials, but the degree of the polynomial is 2 (- 1), so the need to reduce the number of polynomial. The W and X share the secret share of the participant B, and the product of W and X is: Wx = w = x + / +. + (oQ/), (oQ/) Wx x = w, 1 = 1 + 1 = 2. Represented by matrices: - 1 When the upper coefficient matrix is written, it is obviously a nonsingular matrix, and the inverse matrix is denoted as Q/, which is a constant Number matrix. Remember (/, - - -, oQ/) is the first line of the matrix Q/, there are: /wx = 1 + - + - - oQ/wx, 2 - 1 Each participant randomly selected 2 - 1 - 1 - - - / polynomial, and, oQ/, to meet the requirements of B 0 = wx. Definition = "B, oQ/ Obviously: OQ/. 0 = b b 0 = /wx 1 + - - - 2 - 1 = oQ/wx +. B OQ/. = b b B Therefore, the secret is to share the secret and share the secret. A multi-party computation algorithm for multiplication 2.1.3 yuan inverse Set the secret of sharing, the corresponding polynomial is w, and the secret share of participant B is b = W. One yuan Inversion is refers to the participants by B B secret share calculation Q/ w (c) a secret share, but in the process of calculation Can not disclose, Q/ and secret share of the two. The calculation is as follows: Participant B selects the random number B, and selects the random polynomial B () to compute its secret share be = B () to the participant E. To accept all the secret share, e n = Q. Thus all participants share the same random number David - +q + = / s.. Using the multiplicative multi-party computation algorithm, the secret obtained by the secret share is calculated Share w, and sent to the other participants, so it can be recovered by using the Lagrange interpolation, we may assume that = . It is clear that the W - a Q/ C = n, i.e. Q/'s Secret share. 2.2 lock account generation scenarios The lock account generation scheme is an improvement on threshold key management scheme based on Lagrange interpolation polynomial. Its basic idea is that through the threshold secret sharing, all the authentication nodes generate a lock account in a centralized way, and each verification node has a share of the lock private key. This ensures that the lock account private key is distributed in the entire network in the form of the private key share, so it can be centralized management. 2.3 lock account signature scheme The lock account signature algorithm uses the ECDSA signature algorithm, because it is the current block chain project's mainstream signature algorithm, this choice can improve the system compatibility. In a locked account signature generation process, different from the original ECDSA signature algorithm, the private key and the random number to account is in the form of multi-party computation involved in ECDSA signature process; lock account signature verification process with the original ECDSA signature verification algorithm. Therefore, only the lock account signature generation process is described

'''

klcchain

Go1dfish undelete link

unreddit undelete link

Author: klcchain

Dear Bitcoin devs,

I am the author of OCaml-bitcoin [1], a library offering an OCaml

interface

to the official Bitcoin client API. For those who may be unfamiliar

with it,

OCaml is one of those functional programming languages with a very rich

and

expressive type system [2]. Given its emphasis on safety, its

industrial

users are disproportionally found in the aerospace and financial

sectors.

Now, OCaml programmers care a lot about types, because experience has

taught them that deep down most programming errors are just type errors.

From this stems my request: please consider defining more precisely the

type

information associated with each API call in the JSON-RPC reference [3].

To give you a better idea of what I'm talking about, please take a look

at

the API offered by OCaml-bitcoin [4], and the associated type

definitions

[5] (note that these have not been updated for Bitcoin Core 0.10 yet).

I've created the type definitions from information gathered from the

Bitcoin

wiki and from looking at the Bitcoin Core source-code. I wouldn't be

surprised

if it contains errors, because neither the source-code nor the wiki is

very

precise about the actual types being used. As an example, consider type

hexspk_t ("hex representation of script public key"). Is this really

the

same type used in both signrawtransaction and createmultisig?

Improving this situation would pose a minimal burden on bitcoin devs:

all

that would be required is defining the precise set of types used in the

RPC

API, and annotating the RPC calls either in the source-code itself or in

the

API reference documentation. It would make writing bindings such as

mine

far easier and less error prone, and it would have the added advantage

of

better documenting the Bitcoin Core source-code itself.

Also, note that it is not necessary to extend this request to the deep

data structures returned by some API calls. Consider for instance the

gettransaction function of the OCaml-bitcoin API: it returns the raw

JSON

object without any attempt to process it. This is because that's a

fairly

niche facility, and the bindings would balloon in size if I were to

process

every single large return object. Instead, the bindings take the more

pragmatic stance of only processing the parameters and return results

where

a strong type discipline is imperative.

When I raised this issue on IRC a number of questions were posed.

What follows is my attempt to answer them:

Q: What does it matter, if JSON only has a tiny set of types?

A: JSON being the serialisation format is irrelevant. The client

bindings

know that even if a public ECDSA key is serialised as a string, itdoes

not stop being a public ECDSA key, and should only be used where apublic

ECDSA key is expected.Q: What does it matter if the types are not even distinguished in the

C++

source of Bitcoin Core?A: That is unfortunate, because it opens the door to bugs caused by

type

errors. Moreover, even if the C++ source is "stringly-typed" anddoes

not enforce a strong type discipline, that does not mean that thetypes

are not there. Even if a public and private key are bothrepresented

as strings, can you use one where the other is expected? If not,then

they actually have different types!Q: Isn't this a maintenance nightmare, given the changes to Bitcoin

core?

A: Actually, the most burdensome part is what motivated this message:

keeping track of the types used. If the Bitcoin API reference were more precise, keeping the bindings up-to-date would be trivial and even mechanical, because the API is now fairly stable.Thank you very much for your attention, and for all the work you guys

put

into Bitcoin development. It is much appreciated and not acknowledged

often enough!

Best regards,

Dario Teixeira

[1] https://github.com/darioteixeira/ocaml-bitcoin

[2] http://ocaml.org/learn/description.html

[3] https://bitcoin.org/en/developer-reference#bitcoin-core-apis

[4] http://ocaml-bitcoin.forge.ocamlcore.org/apidoc/Bitcoin.ENGINE.html

[5] http://ocaml-bitcoin.forge.ocamlcore.org/apidoc/Bitcoin.html

-----BEGIN PGP SIGNED MESSAGE-----

Hash: SHA512

Bitcoin Core version 0.13.1 is now available from:

https://bitcoin.org/bin/bitcoin-core-0.13.1/

Or through bittorrent:

magnet:?xt=urn:btih:dbe48c446b1113890644bbef03e361269f69c49a&dn;=bitcoin-core-0.13.1&tr;=udp%3A%2F%2Ftracker.openbittorrent.com%3A80%2Fannounce&tr;=udp%3A%2F%2Ftracker.publicbt.com%3A80%2Fannounce&tr;=udp%3A%2F%2Ftracker.ccc.de%3A80%2Fannounce&tr;=udp%3A%2F%2Ftracker.coppersurfer.tk%3A6969&tr;=udp%3A%2F%2Ftracker.leechers-paradise.org%3A6969&ws;=https%3A%2F%2Fbitcoin.org%2Fbin%2F

This is a new minor version release, including activation parameters for the

segwit softfork, various bugfixes and performance improvements, as well as

updated translations.

Please report bugs using the issue tracker at github:

https://github.com/bitcoin/bitcoin/issues

To receive security and update notifications, please subscribe to:

https://bitcoincore.org/en/list/announcements/join/

Compatibility

Microsoft ended support for Windows XP on April 8th, 2014,

an OS initially released in 2001. This means that not even critical security

updates will be released anymore. Without security updates, using a bitcoin

wallet on a XP machine is irresponsible at least.

In addition to that, with 0.12.x there have been varied reports of Bitcoin Core

randomly crashing on Windows XP. It is not clear

what the source of these crashes is, but it is likely that upstream

libraries such as Qt are no longer being tested on XP.

We do not have time nor resources to provide support for an OS that is

end-of-life. From 0.13.0 on, Windows XP is no longer supported. Users are

suggested to upgrade to a newer version of Windows, or install an alternative OS

that is supported.

No attempt is made to prevent installing or running the software on Windows XP,

you can still do so at your own risk, but do not expect it to work: do not

report issues about Windows XP to the issue tracker.

- From 0.13.1 onwards OS X 10.7 is no longer supported. 0.13.0 was intended to work on 10.7+,

0.13.1 now requires 10.8+, and will communicate that to 10.7 users, rather than crashing unexpectedly.

Notable changes

Segregated witness soft fork

allow transaction-producing software to separate (segregate) transaction

signatures (witnesses) from the part of the data in a transaction that is

covered by the txid. This provides several immediate benefits:

**Elimination of unwanted transaction malleability:**Segregating the witness

identifier (txid) of transactions without referencing the witness, which can

sometimes be changed by third-parties (such as miners) or by co-signers in a

multisig spend. This solves all known cases of unwanted transaction

malleability, which is a problem that makes programming Bitcoin wallet

software more difficult and which seriously complicates the design of smart

contracts for Bitcoin.**Capacity increase:**Segwit transactions contain new fields that are not

allows a block containing segwit transactions to hold more data than allowed

by the current maximum block size. Estimates based on the transactions

currently found in blocks indicate that if all wallets switch to using

segwit, the network will be able to support about 70% more transactions. The

network will also be able to support more of the advanced-style payments

(such as multisig) than it can support now because of the different weighting

given to different parts of a transaction after segwit activates (see the

following section for details).**Weighting data based on how it affects node performance:**Some parts of

blocks; other parts of a block can be immediately forgotten (pruned) or used

only for helping other nodes sync their copy of the block chain. One large

part of the immediately prunable data are transaction signatures (witnesses),

and segwit makes it possible to give a different "weight" to segregated

witnesses to correspond with the lower demands they place on node resources.

Specifically, each byte of a segregated witness is given a weight of 1, each

other byte in a block is given a weight of 4, and the maximum allowed weight

of a block is 4 million. Weighting the data this way better aligns the most

profitable strategy for creating blocks with the long-term costs of block

validation.**Signature covers value:**A simple improvement in the way signatures are

(such as hardware wallets), reduces the amount of data the signature

generator needs to download, and allows the signature generator to operate

more quickly. This is made possible by having the generator sign the amount

of bitcoins they think they are spending, and by having full nodes refuse to

accept those signatures unless the amount of bitcoins being spent is exactly

the same as was signed. For non-segwit transactions, wallets instead had to

download the complete previous transactions being spent for every payment

they made, which could be a slow operation on hardware wallets and in other

situations where bandwidth or computation speed was constrained.**Linear scaling of sighash operations:**In 2015 a block was produced that

transaction signature hashes are performed. Other similar blocks, or blocks

that could take even longer to validate, can still be produced today. The

problem that caused this can't be fixed in a soft fork without unwanted

side-effects, but transactions that opt-in to using segwit will now use a

different signature method that doesn't suffer from this problem and doesn't

have any unwanted side-effects.**Increased security for multisig:**Bitcoin addresses (both P2PKH addresses

function known as RIPEMD-160. For P2PKH addresses, this provides about 160

bits of security---which is beyond what cryptographers believe can be broken

today. But because P2SH is more flexible, only about 80 bits of security is

provided per address. Although 80 bits is very strong security, it is within

the realm of possibility that it can be broken by a powerful adversary.

Segwit allows advanced transactions to use the SHA256 hash function instead,

which provides about 128 bits of security (that is 281 trillion times as

much security as 80 bits and is equivalent to the maximum bits of security

believed to be provided by Bitcoin's choice of parameters for its Elliptic

Curve Digital Security Algorithm [ECDSA].)**More efficient almost-full-node security**Satoshi Nakamoto's original

skip downloading and validating some data from historic blocks that are

protected by large amounts of proof of work. Unfortunately, Nakamoto's

method can't guarantee that a newly-started node using this method will

produce an accurate copy of Bitcoin's current ledger (called the UTXO set),

making the node vulnerable to falling out of consensus with other nodes.

Although the problems with Nakamoto's method can't be fixed in a soft fork,

Segwit accomplishes something similar to his original proposal: it makes it

possible for a node to optionally skip downloading some blockchain data

(specifically, the segregated witnesses) while still ensuring that the node

can build an accurate copy of the UTXO set for the block chain with the most

proof of work. Segwit enables this capability at the consensus layer, but

note that Bitcoin Core does not provide an option to use this capability as

of this 0.13.1 release.**Script versioning:**Segwit makes it easy for future soft forks to allow

Script language when those users receive new transactions. Features

currently being researched by Bitcoin Core contributors that may use this

capability include support for Schnorr signatures, which can improve the

privacy and efficiency of multisig transactions (or transactions with

multiple inputs), and Merklized Abstract Syntax Trees (MAST), which can

improve the privacy and efficiency of scripts with two or more conditions.

Other Bitcoin community members are studying several other improvements

that can be made using script versioning.

versionbits. Segwit's version bit is bit 1, and nodes will begin

tracking which blocks signal support for segwit at the beginning of the

first retarget period after segwit's start date of 15 November 2016. If

95% of blocks within a 2,016-block retarget period (about two weeks)

signal support for segwit, the soft fork will be locked in. After

another 2,016 blocks, segwit will activate.

For more information about segwit, please see...[message truncated here by reddit bot]...

Bitcoin puts the current compact-format target and the arbitrary-precision "extraNonce" number there, which increments every time the Nonce field in the block header overflows. Outputs can be anything, but Bitcoin creates one exactly like an IP address transaction. The extranonce contributes to enlarge the domain for the proof of work function. Miners can easily modify nonce (4byte), timestamp ... The Bitcoin system uses the Elliptic Curve Digital Signature (ECDSA) cryptographic algorithm to authenticate Bitcoin transactions. The structure of this report is as follows. We will ﬁrst introduce in Chapter 2 some introductory concepts and explain key deﬁnitions such as decentralised and peer to peer. A brief history of Bitcoin will be given along with a quick background in cryptography ... I am trying to extract the parameters of ECDSA signature used in bitcoin to run some tests. For that i need to obtain : --- r and s , i.e., the ECDSA signature --- H(m) , the hash of the mes... Are all public keys for Elliptical Cryptography practically derived the same way.. meaning there is a ton of overlap between these ECDSA curves? No, there are lots of relevant parameters that go into public key computation: The field size for its coordinates (2^256 - 2^32 - 977 for secp256k1) ECDSA Security in Bitcoin and Ethereum: a Research Survey Hartwig Mayer {hartwig.mayer}@coinfabrik.com CoinFabrik Revised June 28, 2016 Abstract ...

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