4 ms·

Sure but how is this distributed? Does every device hold the chain of blocks?

by coolThingsFirst 11mo ago

dewey 11mo ago
Yes, at least if you want to verify the whole chain.
- OneDeuxTriSeiGo 11mo ago
  Not necessarily. There exists a concept of light mining. It's largely a research topic more than anything deployed currently AFAIK but it's certainly possible and theory wise is secure up to more or less the same bounds as blockchain consensus in general.
OneDeuxTriSeiGo 11mo ago
It depends on the implementation. The naive solution is to have every client hold the full chain. The lightweight solutions come in two flavors, the easy "good enough" solution and the much harder ideal/zero trust solution. The easy solution (light clients) to avoiding carrying the full chain is to simply rely on some set of known/trusted "beacon" servers that you are willing to trust to relay you the chain state and send you what information you need. The hard solution is called a "super light" client. One of the famous super light client implementations is called flyclient[1]. It relies on some tricks with proof of work to only store log2(n) blocks out of the n blocks in the whole chain. It gives you enough security to be able to verify that your chain is valid and constructed from the origin block as well as allowing it to use the longest chain rule to decide what chain is the current "official" chain for the network just like you would with a full chain history. There's another approach called NiPiPoWs [2] (non-interactive proofs of proofs-of-work) which is conceptually similar but is a bit more generally useful (outside of just as a light client system). A few networks adopted it but idk how prevalent its use is nowadays. Note that flyclient, NiPiPoWs and most super light clients tend to rely on properties of proof of work as well as UTxO accounting models which disqualify their use for most networks. Cardano at the very least seems to have figured their own version out [3][4] and it exists kind of as a conceptual redesign of NiPiPoWs but for stake based systems (and actually came out of NiPiPoW research). And of course super light clients still require miners to hold the full chain state generally but there's work[5][6] on how to do "light mining" which of course would allow everybody to abandon old chain state and only keep the data they care about. Note: a lot of the research I linked is inter related as these are the researchers I kept up more closely with last time I was deep in the ecosystem but there's a lot of work on the topic in general coming at these problems from different angles. -------------------------- 1. Flyclient: Super-Light Clients for Cryptocurrencies - https://eprint.iacr.org/2019/226 https://eprint.iacr.org/2019/226 2. Compact Storage of Superblocks for NIPoPoW Applications - https://eprint.iacr.org/2019/1444 https://eprint.iacr.org/2019/1444 3. Mithril: Stake-based Threshold Multisignatures - https://eprint.iacr.org/2021/916 https://eprint.iacr.org/2021/916 4. The velvet path to superlight blockchain clients - https://dl.acm.org/doi/abs/10.1145/3479722.3480999 https://dl.acm.org/doi/abs/10.1145/3479722.3480999 5. Mining in Logarithmic Space - https://dl.acm.org/doi/abs/10.1145/3460120.3484784 https://dl.acm.org/doi/abs/10.1145/3460120.3484784 6. SNACKs: Leveraging Proofs of Sequential Work for Blockchain Light Clients - https://eprint.iacr.org/2022/240 https://eprint.iacr.org/2022/240
- coolThingsFirst 11mo ago
  has there been any useful application of this outside of bitcoin as currency? Seems like a solid technical idea with lots of woo-woo on top of it.
  - OneDeuxTriSeiGo 11mo ago
    Which part? Blockchain in general?
    - coolThingsFirst 11mo ago
      Blockchain and smart contracts.
      - OneDeuxTriSeiGo 11mo ago
        There's certainly application outside of currencies. Bluesky/atproto for example is built on DIDs (decentralised IDs) and IPLD (the data format/standard of IPFS). Both are very heavily rooted in cryptocurrency tech. There's a joke in the atproto community that it's a blockchain but without the currency because of this.
        dboreham 11mo ago
        Neither DID nor IPLD have anything to do with cryptocurrency from a technical perspective. At least no more than do X.509 and ssh.
        OneDeuxTriSeiGo 11mo ago
        IPLD is literally a merkle tree data structure format standardised by IPFS which is heavily rooted in cryptocurrency and in fact has its own cryptocurrency created by the IPFS devs: Filecoin. DIDs were created by cryptocurrency orgs. The standard was created by a bunch of cryptocurrency groups working with the W3C and the entire time it was being developed, it was derided by non-cryptocurrency people as just another way for cryptocurrency to scam people. It doesn't stop being related to cryptocurrency once you realise it's useful.
DJBunnies 11mo ago
Gossip protocol. One can run a pruned node where you only keep block info relating to your associated wallet, but you often keep the whole chain.
kpcyrd 11mo ago
The partial collision is easy to verify but hard to generate, consensus is defined as "longest chain is the source of truth". If some p2p node can present you a longer chain you switch your source of truth to that one.
- dollylambda 11mo ago
  In terms of Bitcoin consensus, it is actually the chain with the most work, not the longest chain.
  - amitav1 11mo ago
    Isn't the longest chain assumed to be the chain with the most work? Not an expert.
    - FabHK 11mo ago
      Generally, yes. But remember that there are difficulty adjustments, and it's conceivable that there are two chains, one being a bit shorter but with higher difficulty, and that can have precedence over the longer but easier one. The point is that you want the chain embodying most work, no matter how long. (And note that a) the difficulty is included in the header that gets hashed, and b) it is easy to check that the block conforms to the specified difficulty.) That's why "heavier-chain-rule" would be a better name than "longest-chain-rule", strictly speaking.

Sure but how is this distributed? Does every device hold the chain of blocks?

dewey 11mo ago

Yes, at least if you want to verify the whole chain.

OneDeuxTriSeiGo 11mo ago
Not necessarily. There exists a concept of light mining. It's largely a research topic more than anything deployed currently AFAIK but it's certainly possible and theory wise is secure up to more or less the same bounds as blockchain consensus in general.

OneDeuxTriSeiGo 11mo ago

It depends on the implementation. The naive solution is to have every client hold the full chain. The lightweight solutions come in two flavors, the easy "good enough" solution and the much harder ideal/zero trust solution. The easy solution (light clients) to avoiding carrying the full chain is to simply rely on some set of known/trusted "beacon" servers that you are willing to trust to relay you the chain state and send you what information you need. The hard solution is called a "super light" client. One of the famous super light client implementations is called flyclient[1]. It relies on some tricks with proof of work to only store log2(n) blocks out of the n blocks in the whole chain. It gives you enough security to be able to verify that your chain is valid and constructed from the origin block as well as allowing it to use the longest chain rule to decide what chain is the current "official" chain for the network just like you would with a full chain history. There's another approach called NiPiPoWs [2] (non-interactive proofs of proofs-of-work) which is conceptually similar but is a bit more generally useful (outside of just as a light client system). A few networks adopted it but idk how prevalent its use is nowadays. Note that flyclient, NiPiPoWs and most super light clients tend to rely on properties of proof of work as well as UTxO accounting models which disqualify their use for most networks. Cardano at the very least seems to have figured their own version out [3][4] and it exists kind of as a conceptual redesign of NiPiPoWs but for stake based systems (and actually came out of NiPiPoW research). And of course super light clients still require miners to hold the full chain state generally but there's work[5][6] on how to do "light mining" which of course would allow everybody to abandon old chain state and only keep the data they care about. Note: a lot of the research I linked is inter related as these are the researchers I kept up more closely with last time I was deep in the ecosystem but there's a lot of work on the topic in general coming at these problems from different angles. -------------------------- 1. Flyclient: Super-Light Clients for Cryptocurrencies - https://eprint.iacr.org/2019/226 https://eprint.iacr.org/2019/226 2. Compact Storage of Superblocks for NIPoPoW Applications - https://eprint.iacr.org/2019/1444 https://eprint.iacr.org/2019/1444 3. Mithril: Stake-based Threshold Multisignatures - https://eprint.iacr.org/2021/916 https://eprint.iacr.org/2021/916 4. The velvet path to superlight blockchain clients - https://dl.acm.org/doi/abs/10.1145/3479722.3480999 https://dl.acm.org/doi/abs/10.1145/3479722.3480999 5. Mining in Logarithmic Space - https://dl.acm.org/doi/abs/10.1145/3460120.3484784 https://dl.acm.org/doi/abs/10.1145/3460120.3484784 6. SNACKs: Leveraging Proofs of Sequential Work for Blockchain Light Clients - https://eprint.iacr.org/2022/240 https://eprint.iacr.org/2022/240

coolThingsFirst 11mo ago
has there been any useful application of this outside of bitcoin as currency? Seems like a solid technical idea with lots of woo-woo on top of it.
- OneDeuxTriSeiGo 11mo ago
  Which part? Blockchain in general?
  - coolThingsFirst 11mo ago
    Blockchain and smart contracts.
    - OneDeuxTriSeiGo 11mo ago
      There's certainly application outside of currencies. Bluesky/atproto for example is built on DIDs (decentralised IDs) and IPLD (the data format/standard of IPFS). Both are very heavily rooted in cryptocurrency tech. There's a joke in the atproto community that it's a blockchain but without the currency because of this.
      - dboreham 11mo ago
        Neither DID nor IPLD have anything to do with cryptocurrency from a technical perspective. At least no more than do X.509 and ssh.
        OneDeuxTriSeiGo 11mo ago
        IPLD is literally a merkle tree data structure format standardised by IPFS which is heavily rooted in cryptocurrency and in fact has its own cryptocurrency created by the IPFS devs: Filecoin. DIDs were created by cryptocurrency orgs. The standard was created by a bunch of cryptocurrency groups working with the W3C and the entire time it was being developed, it was derided by non-cryptocurrency people as just another way for cryptocurrency to scam people. It doesn't stop being related to cryptocurrency once you realise it's useful.

DJBunnies 11mo ago

Gossip protocol. One can run a pruned node where you only keep block info relating to your associated wallet, but you often keep the whole chain.

kpcyrd 11mo ago

The partial collision is easy to verify but hard to generate, consensus is defined as "longest chain is the source of truth". If some p2p node can present you a longer chain you switch your source of truth to that one.

dollylambda 11mo ago
In terms of Bitcoin consensus, it is actually the chain with the most work, not the longest chain.
- amitav1 11mo ago
  Isn't the longest chain assumed to be the chain with the most work? Not an expert.
  - FabHK 11mo ago
    Generally, yes. But remember that there are difficulty adjustments, and it's conceivable that there are two chains, one being a bit shorter but with higher difficulty, and that can have precedence over the longer but easier one. The point is that you want the chain embodying most work, no matter how long. (And note that a) the difficulty is included in the header that gets hashed, and b) it is easy to check that the block conforms to the specified difficulty.) That's why "heavier-chain-rule" would be a better name than "longest-chain-rule", strictly speaking.