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Maybe Blockchain Really Does Have Magical Powers

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Re: Maybe Blockchain Really Does Have Magical Powers

#91

Post by jude- »

pipermerriam wrote: post #18
kfk wrote: post #6

Can somebody explain me how we deal with the increasing size of a blockchain? I get moore's law etc., but other than that? I mean, it's trillions of transactions we are talking about. Federated servers? We break the chain in some way?

Any blockchain client for any chain (Bitcoin, Ethereum, Dogecoin, ...) could very easily implement a storage layer for the underlying blockchain data using a protocol like IPFS. https://ipfs.io/ In this model, individuals would not need to store the entire chain as they could lazily fetch parts of the chain as they are needed. This would allow individuals to store very little of the historical blockchain data if thei…

Don't forget that like BitTorrent, IPFS uses a DHT to route requests. This makes it vulnerable to DHT routing attacks, where an attacker can Sybil the system and censor all of the routes to a block.

Re: Maybe Blockchain Really Does Have Magical Powers

#92

Post by [deleted] »

pipermerriam wrote: post #18
kfk wrote: post #6

Can somebody explain me how we deal with the increasing size of a blockchain? I get moore's law etc., but other than that? I mean, it's trillions of transactions we are talking about. Federated servers? We break the chain in some way?

Any blockchain client for any chain (Bitcoin, Ethereum, Dogecoin, ...) could very easily implement a storage layer for the underlying blockchain data using a protocol like IPFS. https://ipfs.io/ In this model, individuals would not need to store the entire chain as they could lazily fetch parts of the chain as they are needed. This would allow individuals to store very little of the historical blockchain data if thei…

[deleted]

Re: Maybe Blockchain Really Does Have Magical Powers

#93

Post by TillE »

dgreensp wrote: post #74
runeks wrote: post #71

Earlier quoted context omitted.

It shouldn't be necessary either. The proof-of-work is only necessary to avoid a central party wrt. which blockchain is the "right one". Financial institutions are working together with each other, they can easily just agree on which blockchain to follow. But without proof-of-work, the blockchain is just a database with atomic updates. I don't see why they would need a blockchain for that. Ripping Bitcoin in two give…

I think by "blockchain" they mean hashed blocks that include the hash of the previous block and can be synced; basically git.

That doesn't gain you much besides a definite order and a way to check integrity. Useful things to be sure, but nothing a traditional database can't do.

Re: Maybe Blockchain Really Does Have Magical Powers

#94

Post by a3_nm »

DSMan195276 wrote: post #34
valkea wrote: post #25

Earlier quoted context omitted.

How would you ensure the validity of the part of the blockchain you are reading from IPFS?

You may be aware, since you're asking the question, but you really can't without some other information. If you have block D, and want to fetch block A, you don't actually know if it's the real block A unless you also have blocks B, and C. Block D (which you have) contains the hash of block C, which contains the hash of block B, which contains the hash of block A. You need the hash of block A to be able to verify tha…

Not an expert about blockchains, but this makes me wonder whether something close to skip lists " rel="nofollow">https://en.wikipedia.org/wiki/Skip_list> couldn't in principle be implemented in blockchains to avoid this difficulty.

Imagine that block n, when produced, in addition to the hash of the previous block n-1, gave the hash of block n-2, n-4, n-8, ..., n-2^n. This implies that the block size grows linearly, but it should give you the following: whenever you request and obtain a past block A and you have the current block D, you can use these pointers starting at D to easily request and obtain a sequence of blocks (of length log n) which allows you to authenticate A from D. (Of course the algorithm to reach from A is simply to request the first block authenticated in the header of D which is after A.)

Re: Maybe Blockchain Really Does Have Magical Powers

#95

Post by pash »

thefreeman wrote: post #87
tromp wrote: post #39

Earlier quoted context omitted.

> unless you also have blocks B, and C. It suffices to have the headers of blocks B and C. Which, at only 80 bytes per header, is quite manageable.

Are you sure? The header for C will tell you the hash of B. How will you verify the header given for B if you cannot hash the entire block and compare it to the hash you got in the header of C?

Each block's header contains a hash that is the root of a Merkle tree [0] of the transactions in the block. The Merkle-root hash effectively summarizes all of the block's transactions, which allows the overall block hash to be a hash just of the constituents of the header.

Thus if you have the header, you do indeed have everything you need to produce a hash and verify that it matches the hash referenced in the succeeding block. You do not need the information describing individual transactions.

0. https://en.m.wikipedia.org/wiki/Merkle_tree

Re: Maybe Blockchain Really Does Have Magical Powers

#96

Post by baddox »

spullara wrote: post #23
Kinnard wrote: post #13

Earlier quoted context omitted.

Why can't you place multiple bets? Hedging?

Goes back to an old stock prediction scam. You choose 1024 and send 512 the prediction that a stock will go up and 512 the prediction that the same stock will go down. Each day you repeat this process only with the group where you were right. So, 512 -> 256 -> 128 -> 64 -> 32. Eventually you have a small number of people that think you can predict the future and you can ask them for money that you will invest on thei…

It's not clear to me how any system (other than education, which is obviously a very different topic) can solve the gullibility of people who are uneducated about basic game theory and common scams.

Re: Maybe Blockchain Really Does Have Magical Powers

#97

Post by riprowan »

jude- wrote: post #88
jcoffland wrote: post #15

> The technological innovation of a blockchain is that it combines cryptographic signatures with a fault-tolerant distributed database. This is the naive view that has allowed the financial industry to ditch Bitcoin and run with blockchain. The problem that Bitcoin solves and private blockchains do not is called the Byzantine generals problem which did not have a known solution until Bitcoin came along. Private block…

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 Byzcoin propose to resolve the as-yet unresolved problem of mining centralization, which is fundamental to the success of any of these coins?

Re: Maybe Blockchain Really Does Have Magical Powers

#98

Post by riprowan »

semi-extrinsic wrote: post #73
wmf wrote: post #49

Earlier quoted context omitted.

There were known solutions given a fixed set of generals. Nakamoto consensus handles the case of an unknown number of anonymous generals (miners) who may come and go when they please.

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,…

How can you know a general is not a sybil?

Re: Maybe Blockchain Really Does Have Magical Powers

#99

Post by dharma1 »

pipermerriam wrote: post #18
kfk wrote: post #6

Can somebody explain me how we deal with the increasing size of a blockchain? I get moore's law etc., but other than that? I mean, it's trillions of transactions we are talking about. Federated servers? We break the chain in some way?

Any blockchain client for any chain (Bitcoin, Ethereum, Dogecoin, ...) could very easily implement a storage layer for the underlying blockchain data using a protocol like IPFS. https://ipfs.io/ In this model, individuals would not need to store the entire chain as they could lazily fetch parts of the chain as they are needed. This would allow individuals to store very little of the historical blockchain data if thei…

Is IPFS a workable solution, since storage and bandwidth still have real costs to participants? It seems to me it's prone to abuse (botnets storing large amounts of crap on it)

Re: Maybe Blockchain Really Does Have Magical Powers

#100

Post by Avalaxy »

heliumcraft wrote: post #90
Avalaxy wrote: post #72

Earlier quoted context omitted.

Are any of these dapps really in use and making a difference? It seems to me that the listed dapps are mostly technical proof of concepts. For example: a decentralized actuary sounds great, but I find it highly unlikely that the industry is really accepting it. Same goes for flight insurance and option exchanges.

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.
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