Maybe Blockchain Really Does Have Magical Powers • Hacker News Board

Re: Maybe Blockchain Really Does Have Magical Powers

#101

Post by semi-extrinsic » Sat, Sep 03, 2016, 11:00 AM UTC

wmf wrote: post #80

semi-extrinsic wrote: post #73

Earlier quoted context omitted.

Out of curiosity: were there known solutions for an arbitrarily large number of fixed generals? Could a similar solution as with Nakamoto consensus be obtained by having a huge, fixed number of generals, setting some as occupied and using live inputs for those, and then using an alternating series of yes/no votes for the unoccupied generals? (Maybe you'd have trouble with off-by-one errors in the alternating series,…

I assume protocols like Paxos can work with any odd number of generals. Since the generals are anonymous, consider a Sybil attack. If there are N total generals, what's to prevent me from claiming that I am all N generals? If there are N total generals but M entities try to each spam the system with fake generals, how does the system decide?

So you're saying blockchains prevent this because proof-of-work? I.e. that you literally can't run a Sybil attack, because the only way to impersonate N miners is to actually run N miners?

Re: Maybe Blockchain Really Does Have Magical Powers

#102

Post by heliumcraft » Sat, Sep 03, 2016, 11:38 AM UTC

Avalaxy wrote: post #100

heliumcraft wrote: post #90

Earlier quoted context omitted.

Yes and no. Basically there was and still are major obstacles to widespread adoption. For example, VERY recently stuff like https://metamask.io/ and Mist has been released, which make this sort of apps more accessible to the average user. light clients protocol are still under development, there is lots of important scalability improvements on the roadmap (proof of stake, instantaneous transactions, unlimited txs, et…

Yea that last point is where I'm struggling with. I've done quite a bit of software dev in the Bitcoin space. I built at least 5 different wallet apps (mostly contracting), but I'm still struggling with how I can use blockchains to build other stuff than payment systems. The distributed storage definitely sounds interesting and I can see how that would benefit certain scenarios.

Have you given a look at ethereum? Generally the community there doesn't care too much about wallets, that should tell you something :)

For usage, one of the mains advantages would be for systems that you don't want to use a centralized system anymore - for whatever reason from privacy to control over your data to simply infrastructure reasons (i.e you want 100% uptime and no censorship), and want to transform it into a decentralized system.

Re: Maybe Blockchain Really Does Have Magical Powers

#103

Post by wmf » Sat, Sep 03, 2016, 8:23 PM UTC

semi-extrinsic wrote: post #101

wmf wrote: post #80

Earlier quoted context omitted.

I assume protocols like Paxos can work with any odd number of generals. Since the generals are anonymous, consider a Sybil attack. If there are N total generals, what's to prevent me from claiming that I am all N generals? If there are N total generals but M entities try to each spam the system with fake generals, how does the system decide?

So you're saying blockchains prevent this because proof-of-work? I.e. that you literally can't run a Sybil attack, because the only way to impersonate N miners is to actually run N miners?

Yes. (Modulo arguments about the definition of "blockchain".)

Re: Maybe Blockchain Really Does Have Magical Powers

#104

Post by lefkok » Sun, Sep 04, 2016, 9:41 PM UTC

riprowan wrote: post #97

jude- wrote: post #88

Earlier quoted context omitted.

No. First, solutions to Byzantine agreement for known numbers of processes predate Bitcoin. Second, Nakamoto Consensus is not Byzantine agreement. Byzantine agreement forbids committed writes from being reverted, and each replica sees the same history of writes. However, Nakamoto Consensus only offers probabilistic write durability (our transactions can get orphaned arbitrarily far into the future), and different pee…

Byzcoin is interesting but like Bitcoin its security model depends on massively decentralized mining. Mining is a function of turning electricity into coins. Since coin generation rate is fixed through a difficulty adjustment, mining becomes a winner-take-all game where only those miners with the lowest electricity costs can effectively compete. Thus the system collapses quickly into a mining oligarchy. What does Byz…

Any proof-of-work based system has this problem, especially when the PoW is outsourceable. However, I believe you are missing the point of Byzcoin, which is that if there is a set of decentralised miners we can still get the strongly consistent, final guarantees of Byzantine agreement in a scalable way.

ByzCoin has PoW to be Bitcoin compatible, but it can change to PoS or PoA or even permissioned systems (e.g hyperledger).