4 ms·

Would be better if someone could come up with a problem that blockchains solve.

petertodd 8y ago
There's a good chance you're using a blockchain(1) to visit this website: the SSL certificate that protects your connection is published in a Certificate Transparency blockchain. If you're using Chrome, your browser verified a proof that the certificate was in fact in one of the CT blockchains. Being a blockchain, auditors (like the sysadmins at hacker news) can be sure they have the complete set of all certificates, and thus be sure they can detect any forgeries. 1) A blockchain is simply a chain of blocks. The key thing they do is allow auditing mechanisms to be sure they have the complete set of data contained in them. They're really a very simple and useful idea, which unfortunately has been hyped up by a bunch of scammers and semi-scammers. The consensus mechanisms used to secure blockchains are the interesting part, not the blockchains themselves. Although for many applications - Certificate Transparency being one of them - boring old trusted third parties seem to be good enough. That said, if you have a stronger decentralized chain available too, you can always publish commitments to the state of your centralized chain in the decentralized chain, improving security at relatively little cost. I wrote up a particularly scalable version of that idea here: https://petertodd.org/2017/scalable-single-use-seal-asset-transfer https://petertodd.org/2017/scalable-single-use-seal-asset-tr...
- knorker 8y ago
  > Certificate Transparency Only in the sense that "git" also is a blockchain. In other words: nothing relevant to cryptocurrencies, really.
  - petertodd 8y ago
    But that's the thing: git is very close to a blockchain! The only thing that's missing from git that makes it not quite a blockchain is that the way we use git doesn't expect there to be a linear series of commits. But with relatively little effort you can add that to git, making a blockchain out of it. What blockchains do in cryptocurrencies is not magic: they're just the basic auditing mechanism that allows everyone with a full node to verify that all the rules are being followed by parsing all the transactions. The simplest way to do that is with a linear chain of blocks that you validate, starting at block zero. All the "magic" is in the consensus mechanisms that decide which chain of blocks is in fact the real chain, not the blockchains themselves.
    - tscs37 8y ago
      Git is a blockchains. I don't see any rules that a consensus algorithm needs to be non-human or that only a single chain can be authorative. Git is a blockchain that has none of the usual problems of blockchains since the arbiter is a human and they can do as they please. Argreement between humans is a social procedure.
      - petertodd 8y ago
        My only real disagreement with you is I'd call Git a blockdag, because it's a more general directed acyclic graph rather than a linear chain. But that's just a disagreement about what's more helpful terminology.
    - admax88q 8y ago
      I think the term "blockchain" implies more than just a merkle-tree but some level of distributed concensus. A plain merkle-tree or merkle-list. Such technology has been around for a while before "blockchain" was such a hyped technology.
    - knorker 8y ago
      I think you missed my point. When people talk about blockchains they're not talking about a DAG, even they're related. Playing a semantics game gets us nowhere. I could try to be more specific and say distributed blockchain every time. But then you'll say oh but git does merging and network, so it's distributed. I'll use a new phrase, and you'll point out that RAM is usually not the same chip as the CPU, so it's distributed, etc… etc… I'm certainly not saying anything is magic. If anyone says cryptocurrencies are magic or Holy, then it's their proponents. I'm saying "but why…?" to the explanation, not "what sorcery is this?!". You might as well say that "algorithms" are used in crimecurrencies, so "you're using the same technology to visit this web site". In short: By no meaningful definition has blockchains come up with a use case.
  - fixermark 8y ago
    I believe parent poster's point is that there are other uses for blockchains than (implied by the GP) cryptocurrency.
    - knorker 8y ago
      Yes, but there aren't.
tomjen3 8y ago
Here is one: without a block chain to prove you developed something first you have to write it in an engineering log, in your handwriting and pay a fortune to store that some place safe, probably environmentally secured, etc. With a block chain you can pay 1 sat (ie less than 1/100 penny) to have your git hash stamped forever into the blockchain. You can then pay nearly nothing to have it safely stored until you need to prove it, at which point you have very, very good evidence to prove you had what you claimed, when you did. You can also stamp the git hash into your twitter, (you can, as of this writing, delete but not edit tweets), but that assumes you are counting on Twitter to be around 30+ years.
- theamk 8y ago
  ... or sign it using cryptographic timestamp service, and keep certificate? Use multiple timestamp services if you want more assurance. see also: https://www.globalsign.com/en/blog/what-is-timestamping-how-does-it-work/ https://www.globalsign.com/en/blog/what-is-timestamping-how-... see also free services: https://stackoverflow.com/questions/25052925/does-anyone-know-a-freetrial-timestamp-server-service https://stackoverflow.com/questions/25052925/does-anyone-kno...
  - tomjen3 8y ago
    There are more than one way to do it, of course, but you are relying on them never to lose control of their private keys.
- knorker 8y ago
  I'll agree that this makes it easier. But why? Have you ever, in your life, needed to do this? Do you know anyone who has? Have you heard of anyone who has? This problem sometimes comes up in thought experiments, and sometimes involves convoluted solutions such as bouncing signals off of celestial bodies to produce a time delay. I have never needed to do this. And either way the actual cost for society to do this with blockchains is huge, in energy. You're not paying it, but the cost is there. Or you could just do it the traditional way: Put it on pastebin. Hell, put it on a couple of cloud services, who will likely have logs about upload times. Maybe there are cases, where you want to guard yourself against someone reinventing your industry secret and claiming IP theft saying you copied them. It won't help against a patent lawsuit, I'm pretty sure, since you didn't publish. And publishing is the trade you make with society in order to get monopoly for 18-20 years via a patent. But more importantly: This NEVER needs to be a blockchain. This is not a use for a blockchain. There is nothing chain about it. You just want your blob signed. You could build a service in a weekend that does nothing but sign "I saw the following hash on 2018-05-24: 82390182903120", and run it for no cost (not 0.5% of world electricity). Send your hash to 100 places and boom, done.

There's a good chance you're using a blockchain(1) to visit this website: the SSL certificate that protects your connection is published in a Certificate Transparency blockchain. If you're using Chrome, your browser verified a proof that the certificate was in fact in one of the CT blockchains. Being a blockchain, auditors (like the sysadmins at hacker news) can be sure they have the complete set of all certificates, and thus be sure they can detect any forgeries. 1) A blockchain is simply a chain of blocks. The key thing they do is allow auditing mechanisms to be sure they have the complete set of data contained in them. They're really a very simple and useful idea, which unfortunately has been hyped up by a bunch of scammers and semi-scammers. The consensus mechanisms used to secure blockchains are the interesting part, not the blockchains themselves. Although for many applications - Certificate Transparency being one of them - boring old trusted third parties seem to be good enough. That said, if you have a stronger decentralized chain available too, you can always publish commitments to the state of your centralized chain in the decentralized chain, improving security at relatively little cost. I wrote up a particularly scalable version of that idea here: https://petertodd.org/2017/scalable-single-use-seal-asset-transfer https://petertodd.org/2017/scalable-single-use-seal-asset-tr...

knorker 8y ago
> Certificate Transparency Only in the sense that "git" also is a blockchain. In other words: nothing relevant to cryptocurrencies, really.
- petertodd 8y ago
  But that's the thing: git is very close to a blockchain! The only thing that's missing from git that makes it not quite a blockchain is that the way we use git doesn't expect there to be a linear series of commits. But with relatively little effort you can add that to git, making a blockchain out of it. What blockchains do in cryptocurrencies is not magic: they're just the basic auditing mechanism that allows everyone with a full node to verify that all the rules are being followed by parsing all the transactions. The simplest way to do that is with a linear chain of blocks that you validate, starting at block zero. All the "magic" is in the consensus mechanisms that decide which chain of blocks is in fact the real chain, not the blockchains themselves.
  - tscs37 8y ago
    Git is a blockchains. I don't see any rules that a consensus algorithm needs to be non-human or that only a single chain can be authorative. Git is a blockchain that has none of the usual problems of blockchains since the arbiter is a human and they can do as they please. Argreement between humans is a social procedure.
    - petertodd 8y ago
      My only real disagreement with you is I'd call Git a blockdag, because it's a more general directed acyclic graph rather than a linear chain. But that's just a disagreement about what's more helpful terminology.
  - admax88q 8y ago
    I think the term "blockchain" implies more than just a merkle-tree but some level of distributed concensus. A plain merkle-tree or merkle-list. Such technology has been around for a while before "blockchain" was such a hyped technology.
  - knorker 8y ago
    I think you missed my point. When people talk about blockchains they're not talking about a DAG, even they're related. Playing a semantics game gets us nowhere. I could try to be more specific and say distributed blockchain every time. But then you'll say oh but git does merging and network, so it's distributed. I'll use a new phrase, and you'll point out that RAM is usually not the same chip as the CPU, so it's distributed, etc… etc… I'm certainly not saying anything is magic. If anyone says cryptocurrencies are magic or Holy, then it's their proponents. I'm saying "but why…?" to the explanation, not "what sorcery is this?!". You might as well say that "algorithms" are used in crimecurrencies, so "you're using the same technology to visit this web site". In short: By no meaningful definition has blockchains come up with a use case.
- fixermark 8y ago
  I believe parent poster's point is that there are other uses for blockchains than (implied by the GP) cryptocurrency.
  - knorker 8y ago
    Yes, but there aren't.

tomjen3 8y ago

Here is one: without a block chain to prove you developed something first you have to write it in an engineering log, in your handwriting and pay a fortune to store that some place safe, probably environmentally secured, etc. With a block chain you can pay 1 sat (ie less than 1/100 penny) to have your git hash stamped forever into the blockchain. You can then pay nearly nothing to have it safely stored until you need to prove it, at which point you have very, very good evidence to prove you had what you claimed, when you did. You can also stamp the git hash into your twitter, (you can, as of this writing, delete but not edit tweets), but that assumes you are counting on Twitter to be around 30+ years.

theamk 8y ago
... or sign it using cryptographic timestamp service, and keep certificate? Use multiple timestamp services if you want more assurance. see also: https://www.globalsign.com/en/blog/what-is-timestamping-how-does-it-work/ https://www.globalsign.com/en/blog/what-is-timestamping-how-... see also free services: https://stackoverflow.com/questions/25052925/does-anyone-know-a-freetrial-timestamp-server-service https://stackoverflow.com/questions/25052925/does-anyone-kno...
- tomjen3 8y ago
  There are more than one way to do it, of course, but you are relying on them never to lose control of their private keys.
knorker 8y ago
I'll agree that this makes it easier. But why? Have you ever, in your life, needed to do this? Do you know anyone who has? Have you heard of anyone who has? This problem sometimes comes up in thought experiments, and sometimes involves convoluted solutions such as bouncing signals off of celestial bodies to produce a time delay. I have never needed to do this. And either way the actual cost for society to do this with blockchains is huge, in energy. You're not paying it, but the cost is there. Or you could just do it the traditional way: Put it on pastebin. Hell, put it on a couple of cloud services, who will likely have logs about upload times. Maybe there are cases, where you want to guard yourself against someone reinventing your industry secret and claiming IP theft saying you copied them. It won't help against a patent lawsuit, I'm pretty sure, since you didn't publish. And publishing is the trade you make with society in order to get monopoly for 18-20 years via a patent. But more importantly: This NEVER needs to be a blockchain. This is not a use for a blockchain. There is nothing chain about it. You just want your blob signed. You could build a service in a weekend that does nothing but sign "I saw the following hash on 2018-05-24: 82390182903120", and run it for no cost (not 0.5% of world electricity). Send your hash to 100 places and boom, done.