Hacker News

Algorand Consensus Protocol(developer.algorand.org)

63 pointsnemoniac posted 2 days ago15 Comments
15 Comments:
vessenes said a day ago:

Written as someone who knows a reasonable amount about crypto system design, I would like this page to be written with a fixed audience in mind. It’s frustrating to read because it is at once ‘high level’ with cute diagrams, and then technical (“private key plus data into VRF gives a lottery”).

At any rate, it would be nice to see something written for a more technical user that’s not just a formal spec (although that would be okay, too.)

One salient question I have is: during the account choosing phase in which the VRF is applied to each account held in a given wallet, what is the precise mechanism by which some accounts are chosen? Is it a difficulty mechanism, where the VRF(account, some blockheader data) must be less than a given number? If so, how and why does the number change?

josh2600 said a day ago:

I mean you can just read Silvio’s paper: https://arxiv.org/abs/1607.01341

My understanding on how the accounts are chosen is that they have a global list of users that have opted in to validate and they pick one person at random to create the block and then 1000 people at random to validate it. If you get 501 validations back, then you have a block.

The attack I always thought about but never got an answer to was: what if you pay for the lottery winners to collude? Certainly if you offer some amount of money for the block producers only on the condition that you get 501+the block creator in a given block you could probably sign a bad block, right? It’s unclear what the consequences of that would be if the block’s signatures still have to be valid but you could maybe craft something bad.

I don’t know, all of this thinking is from when I first talked to Silvio at IACR so it’s been a long time. It’s possible all of my knowledge is way out of date or wrong.

Anyways, I wish them luck, they’ve certainly got a big thing going.

vessenes said 6 hours ago:

Generally Bitcoin has solved this by social and denominative means — definitionally if a majority of miners sign a stream of blocks that ‘break the rules’ then, that is the truth and the miners have chosen new rules.

Socially if this is signing a block with a bug, miners have historically colluded to rewrite history.

If on the other hand the new blocks embed protocol changes, then we move to names: is it still ‘Bitcoin’? If not then there is a hard fork with a new community. This is the BCH, BSV and ETC story.

The answer to your question about Algorand is probably similar, unless the scheme has some novel mechanism to prune hard forks, or a way to radically include them.

quantum_state said a day ago:

I am very curious to know about this as well ... hope someone in the know would provide some clue ... :-)

mmahut said a day ago:

I really like Algorand, too bad for all the patents surrounding the protocol, it could have been the next standard.

aeternum said 2 days ago:

This does not address the bootstrapping problem. Without some existing peer or root to trust, how do I know which is the real Algorand blockchain?

Some other group could follow this exact protocol and also call their blockchain Algorand.

tromp said 2 days ago:

Just as with Bitcoin, you have to know the genesis block.

Which is generally hardcoded in the client you run. So in that sense you trust the binaries you download, or the source code that you compile. The advantage of PoW consensus is that it's much easier to tell the real chain from a fake one, as the latter will not have much more work performed on it.

Even with the genesis block fixed, control of the initial keys embedded in it allows you to generate arbitrary alternative blockchain histories that without PoW are difficult to distinguish from the "real" one.

aeternum said a day ago:

With a PoW blockchain you do not need to trust the genesis block. You can calculate the total amount of work represented by any blockchain which provides an independent measure of trust. Total proof of work can be calculated with just a copy of the blockchain data without trusting the software client. Nothing like that exists with proof-of-stake.

If the assumption is that downloaded binaries must be trusted, one could simply use a key embedded inside that binary to verify the identity of a centralized database. No need for proof-of-stake.

einarvollset said 2 days ago:

Nice to see applied to a different domain, but this is a reasonably standard randomized Byzantine fault tolerant consensus protocol, or? Nothing wrong with that of course, just curious why it was deemed newsworthy.

AlexCoventry said 2 days ago:

Which prior protocol does it seem most similar to, to you?

brynb said 2 days ago:

Oh, hey there, Coventry :) I’d be curious to know the same, as well as to hear a comparison between Algorand and: 1) recent work on aBFT protocols, many of which don’t seem to require any kind of staking, and... 2) Chainlink’s off-chain aggregation protocol’s consensys mechanism

ncmncm said 2 days ago:

Is this the first example of a blockchain-related algorithm that is of actual, practical use?

exdsq said a day ago:

I assume, if this algorithm is of actual use to you, the algorithm used by Cardano and Tezos are also of actual practical use. These are my three favourite projects (including Algorand). I am particularly biased though as I work on Cardano.

josh2600 said a day ago:

Does cardano do on-chain governance? On-chain governance scares me.

said 2 days ago:
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