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Offline santaclause102

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Interesting discussion on 'weak subjectivity' and proof of stake
« on: December 22, 2014, 04:19:38 PM »

https://blog.ethereum.org/2014/11/25/proof-stake-learned-love-weak-subjectivity/#comment-1712787612 - see the comments and the discussion between Vitalik, Paul S and Jae Kwon.

Weak subjectivity means relying on friends of core developers to provide checkpoints to avoid Long Range Nothing at Stake attacks.

Vitalik:
Quote
I would totally not support subjectivity at the multi-hour timescales that nxt and bitshares are currently going with.

I am not aware of a discussion or a documentation about such details for BitShares. How are checkpoints handled for BitShares at the moment?

Offline toast

Re: Interesting discussion on 'weak subjectivity' and proof of stake
« Reply #1 on: December 22, 2014, 04:38:49 PM »
Well right now the consensus model is that vikram is the checkpoint dictator every time we have a major breaking change. Afterwards, getting 51 delegates who have high approval to sign a chain + now allowing local clients to rewind farther than a few rounds is equivalent to getting all the delegates to sign off on a checkpoints.json file that the delegates + clients can all agree to at that time.
Do not use this post as information for making any important decisions. The only agreements I ever make are informal and non-binding. Take the same precautions as when dealing with a compromised account, scammer, sockpuppet, etc.

Offline vbuterin

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Re: Interesting discussion on 'weak subjectivity' and proof of stake
« Reply #2 on: December 22, 2014, 09:10:17 PM »
> Weak subjectivity means relying on friends of core developers to provide checkpoints to avoid Long Range Nothing at Stake attacks.

Correction: that's friends or core developers :) (or blockchain.info for that matter)

Offline santaclause102

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Re: Interesting discussion on 'weak subjectivity' and proof of stake
« Reply #3 on: December 22, 2014, 09:43:51 PM »
> Weak subjectivity means relying on friends of core developers to provide checkpoints to avoid Long Range Nothing at Stake attacks.

Correction: that's friends or core developers :) (or blockchain.info for that matter)
:) that was funny.

What I didn't understand from the conversation below your blog post was how checkpoints are related to deposits. So you (you and Truthcoin Paul) were talking about checkpoint/weak subjectivity and then you say:
Quote
Yeah, the plan is to make the deposit length at least a few months and my pref is a year. I would totally not support subjectivity at the multi-hour timescales that nxt and bitshares are currently going with. And the idea is precisely to make security deposits very large; a large part of the whole point of PoS is that via deposits the security margin can be made to be larger than the reward, which is not the case with PoW, hence why PoS is cheaper (I completely forgot to add that argument into my post for some reason)

Do you mean tendermint like deposits here?

And how does your solution differ from the solution toast outlined above (51% of delegates sign on a checkpoint from time to time)? I mean your solution doesn't involve delegates so it obviously differs but I didn't really get yet what your PoS (incl. checkpoints and deposits) proposal boils down to.

Offline Rune

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Re: Interesting discussion on 'weak subjectivity' and proof of stake
« Reply #4 on: December 22, 2014, 10:32:55 PM »
> Weak subjectivity means relying on friends of core developers to provide checkpoints to avoid Long Range Nothing at Stake attacks.

Correction: that's friends or core developers :) (or blockchain.info for that matter)

There's one thing I've been wondering in this checkpoint debate. Doesn't it require more trust to download a private-key-holding client than to accept a checkpoint from a given source? So if only new users are at risk of NaS, and they need to choose a trusted source to download a client from anyway, can't that trusted source you download the client from also provide you with the checkpoint without increasing the level of trust required at all?

Offline vbuterin

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Re: Interesting discussion on 'weak subjectivity' and proof of stake
« Reply #5 on: December 23, 2014, 12:30:45 PM »
> Weak subjectivity means relying on friends of core developers to provide checkpoints to avoid Long Range Nothing at Stake attacks.

Correction: that's friends or core developers :) (or blockchain.info for that matter)

There's one thing I've been wondering in this checkpoint debate. Doesn't it require more trust to download a private-key-holding client than to accept a checkpoint from a given source? So if only new users are at risk of NaS, and they need to choose a trusted source to download a client from anyway, can't that trusted source you download the client from also provide you with the checkpoint without increasing the level of trust required at all?

Nope not all that much. Many people in this space actually do implicitly operate under the assumption that every user wrote their code themselves, which I tried to fix at https://blog.ethereum.org/2014/09/02/software-bounded-rationality/

However, there is one thing you do need to be careful of: with software, you can wait two weeks before installing a particular version, so that if there are bugs or malicious flaws someone else will find them first. In order for checkpoints to provide the same assurance, the checkpoint should ideally also have been displayed in public for at least two weeks. If software updates versions frequently, putting checkpoints into software client versions is a reasonable way of doing this.

Offline graffenwalder

Re: Interesting discussion on 'weak subjectivity' and proof of stake
« Reply #6 on: December 23, 2014, 08:48:48 PM »
Congratulations vbuterin, you're the third winner in the 10 * 5 BITUSD Christmas give away.
PM me your BTS account and I'll send you your price.

Offline santaclause102

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Re: Interesting discussion on 'weak subjectivity' and proof of stake
« Reply #7 on: December 23, 2014, 08:56:58 PM »
Congratulations vbuterin, you're the third winner in the 10 * 5 BITUSD Christmas give away.
PM me your BTS account and I'll send you your price.
how did he get to this honor?

Offline graffenwalder

Re: Interesting discussion on 'weak subjectivity' and proof of stake
« Reply #8 on: December 23, 2014, 09:01:11 PM »
Congratulations vbuterin, you're the third winner in the 10 * 5 BITUSD Christmas give away.
PM me your BTS account and I'll send you your price.
how did he get to this honor?

Would be interesting to see if he has an BTS account.
And with that being said.

Congratulations delulo, you're the fifth winner in the 10 * 5 BITUSD Christmas give away.
PM me your BTS account and I'll send you your price.

Will you be the first to claim your price?

 

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