Maybe Blockchain Really Does Have Magical Powers • Hacker News Board

Re: Maybe Blockchain Really Does Have Magical Powers

#81

Post by wpietri » Fri, Sep 02, 2016, 10:55 PM UTC

runeks wrote: post #71

zby wrote: post #69

Earlier quoted context omitted.

The trustlesness comes with a heavy price of Proof of Work with its wastefulness, complexity and vulnerability to various attacks. I can understand why financial institutions don't want that part.

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…

> 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.

I have been asking this question for a long time and not yet seen a satisfactory answer. At this point I'm sure that either I or a bunch of blockchain advocates are missing something important. Glad to know somebody else sees the problem too.

Re: Maybe Blockchain Really Does Have Magical Powers

#82

Post by aeijdenberg » Fri, Sep 02, 2016, 11:01 PM UTC

artursapek wrote: post #54

wc- wrote: post #43

Earlier quoted context omitted.

Someone more familiar with this than me feel free to correct me here, but this is my basic understanding: If you think of your bitcoins as following a path from address to address, the pruning process would retain the final node or two on that path but discard any previous nodes. So your 10 year old bitcoins at address X are still the most recent node on that chain and are kept around. However, once they are finally…

Yep. If people are familiar with Redis, it would be much like how Redis periodically rewrites its append-only-file to make it smaller. So you go from a file with full history like SET a 2 SET b 4 SET a 6 SET b 10 SET a 20 to just SET a 20 SET b 10 The snapshot would just retain resulting balances at a certain block height, and no history of how they got there (previous transactions). If people wanted that history it…

Would be interested in your feedback on Verifiable Maps as implemented at https://www.continusec.com/ which can give verifiable answers to specific questions such as what is the current balance as well as a full history log of all mutations to the map.

Re: Maybe Blockchain Really Does Have Magical Powers

#83

Post by wpietri » Fri, Sep 02, 2016, 11:13 PM UTC

zby wrote: post #47

jnbiche wrote: post #9

Earlier quoted context omitted.

> tldr; this whole breakthru in technology called the blockchain isn't a new idea at all I haven't read the article, and I been tired of blockchain hype for multiple years, but if this is an accurate tldr of the article, it isn't true at all. Blockchains are far more than simple shared ledgers. They're trustless shared ledgers, which is a huge leap forward from simple shared ledgers, and a pretty big deal for financi…

The point is that the trustlesness is not needed for the applications mentioned in the original report. Also they probably don't want Proof of Work for its wastefulness.

Or, I'm sure, its relative slowness. LMAX can do millions of transactions per second. [1] Bitcoin is doing, what, 3 TPS? And I don't mean 3 million, just 3. (I get that from ~1600 transactions per block [2] and 1 block per 10 minutes.)

Back when I was doing trading systems, my traders would have murdered me if my response time graph looks like the Bitcoin one does. [3]

[1] http://martinfowler.com/articles/lmax.html

[2] https://blockchain.info/charts/n-transactions-per-block

[3] https://blockchain.info/charts/avg-confirmation-time?timespa...

Re: Maybe Blockchain Really Does Have Magical Powers

#84

Post by TD-Linux » Fri, Sep 02, 2016, 11:21 PM UTC

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…

This assumes you already know Block D is genuine. You can only know this if you have already verified all the previous blocks. You can prune them away afterwards, but you still must download and run computation over them once.

Re: Maybe Blockchain Really Does Have Magical Powers

#85

Post by TD-Linux » Fri, Sep 02, 2016, 11:23 PM UTC

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…

Bitcoin already has a p2p layer like torrents or IPFS that can quickly download the block chain from many peers. On a sufficiently fast internet connection you get limited by CPU speed verifying signatures.

Re: Maybe Blockchain Really Does Have Magical Powers

#86

Post by TD-Linux » Fri, Sep 02, 2016, 11:31 PM UTC

wc- wrote: post #43

DougN7 wrote: post #42

Earlier quoted context omitted.

I'm a blockchain noob, but what about people like me that own some bitcoin, but don't touch them for a decade. I imagine my ownership of said coins would be in that part that is truncated/archived/hashed. So how would I then use them?

Someone more familiar with this than me feel free to correct me here, but this is my basic understanding: If you think of your bitcoins as following a path from address to address, the pruning process would retain the final node or two on that path but discard any previous nodes. So your 10 year old bitcoins at address X are still the most recent node on that chain and are kept around. However, once they are finally…

In Bitcoin, these final nodes are called UTXOs (unspent transaction outputs), and indeed if you use chain pruning or a light client, they are all you need. They also need to be searched quickly to verify transactions, so they are usually kept in RAM. Because they cannot be pruned, there is a soft fork being developed called SegWit that changes the accounting so that transactions cost more if they create many unspent outputs, or cost less if they spend more outputs than they create.

Re: Maybe Blockchain Really Does Have Magical Powers

#87

Post by thefreeman » Fri, Sep 02, 2016, 11:37 PM UTC

tromp wrote: post #39

DSMan195276 wrote: post #34

Earlier quoted context omitted.

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…

> 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?

Re: Maybe Blockchain Really Does Have Magical Powers

#88

Post by jude- » Fri, Sep 02, 2016, 11:38 PM UTC

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 peers can see divergent histories of arbitrary length even under normal operation.

Third, Byzantine agreement is defined in terms of the set of peers. Systems where the agreement protocol does not know the number of peers cannot solve the Byzantine agreement problem, since they can't prove that no more than f of 3f+1 peers are faulty (neither quantity is known to the system).

Fourth, open-membership Byzantine agreement was published this year: http://hackingdistributed.com/2016/08/04/byzcoin/. The membership set changes every "block", but the peers in the set during the current epoch are known.

EDIT: typo

Re: Maybe Blockchain Really Does Have Magical Powers

#89

Post by [deleted] » Fri, Sep 02, 2016, 11:38 PM UTC

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…

[deleted]

Re: Maybe Blockchain Really Does Have Magical Powers

#90

Post by heliumcraft » Fri, Sep 02, 2016, 11:44 PM UTC

Avalaxy wrote: post #72

heliumcraft wrote: post #67

Earlier quoted context omitted.

http://dapps.ethercasts.com/

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, etc..). Decentralized storages such as swarm, IPFS, maidsafe etc.. are still under development. Overall, there is a lot of experimentation and throwing stuff at the wall to see what sticks. If you want to develop production ready stuff that your grandma can use today, you might be better off waiting 2-5 years until it's sufficiently mature and all the use cases are obvious. If you like to experiment with new paradigms, new architectures, and explore new business models then it's an exciting field to be in.