9 ms·

I believe certificate transparency http://www.certificate-transparency.org/ http://www.certificate-transparency.org/ is based on blockchain technology. (Haven't

I believe certificate transparency http://www.certificate-transparency.org/ http://www.certificate-transparency.org/ is based on blockchain technology. (Haven't studied it in detail, just happened to notice this new SCT field in my Let's Encrypt certificate recently.)

tialaramex 6y ago
Certificate Transparency is mostly built out of a Merkle tree hash which is a 1979 idea from Ralph Merkle (also the M in MD5 and various other things) and ordinary digital signature technology of the same sort used in those certificates. An observer can verify that the log remains consistent (thus nothing can be retrospectively inserted or removed as opposed to appended - without an observer detecting this) and that specific things that carry SCTs saying they were logged were, in fact, appended to the log. This isn't a blockchain. If you want to call it "blockchain technology" you can probably squint hard enough to do that, see also various "Internet technology" companies from the turn of the century that just consisted of a normal company plus a web site most of which were failures - but I don't think you learn anything from it. And in fact not all of CT is actually finished and deployed. There ought to be a Gossip system, which would allow clients to er, gossip about things they'd learned, and thus discover any inconsistencies which they can't see individually. e.g if from Turkey the log seems to show one entry for this www.google.com certificate but when seen from France the entry is different, Gossip potentially allows a Turkish client to tell a French client what it saw and the alarm is sounded. Gossip is necessary to ensure logs can't deliver a split horizon view and to loop back the trust from SCTs to actual log records, but it's fraught to do this in a privacy-preserving manner. The actual deployed system works for two reasons, which I've no doubt would horrify Blockchain proponents who worship at the altar of distributed consensus: 1. The actors (root Certificate Authorities, trust stores) are basically honest. They're not always competent or diligent or open but they mostly don't deliberately spread falsehoods, so the records in CT would probably be almost as useful even if it was just a huge text file or something with no cryptographic basis of trust. 2. The main clients mandating CT are Safari and Chrome and both of them require that certificates are logged with Google (and somebody else, but you can pick who). So attacks that require falsifying the logs can't work unless Google does them. If you're Google this is enough. If you're not Google it's still pretty satisfying, why would Google build this complicated and relatively expensive system just to lie to me about something I otherwise would have no way to know about in the first place?
- tialaramex 6y ago
  > (also the M in MD5 and various other things) I should correct this. MD stands for "Message Digest" which is what this type of algorithm is for. So then it's just a coincidence that it's also the initials of (Ralph) Merkle and (Ivan) Damgård whose method for making a cryptographic hash out of a compression function was used.
lucb1e 6y ago
Open site, use the search box on the top right to look for merely the keyword "blockchain", find 1 hit which says: > We are not making "the" blockchain, and we do not claim to support decentralisation. This does not use a blockchain in the bitcoin/ethereum/... sense of the word. Perhaps in a "git" sense of the word, but I don't think that's what OP meant when asking for legitimate uses.

tialaramex 6y ago

Certificate Transparency is mostly built out of a Merkle tree hash which is a 1979 idea from Ralph Merkle (also the M in MD5 and various other things) and ordinary digital signature technology of the same sort used in those certificates. An observer can verify that the log remains consistent (thus nothing can be retrospectively inserted or removed as opposed to appended - without an observer detecting this) and that specific things that carry SCTs saying they were logged were, in fact, appended to the log. This isn't a blockchain. If you want to call it "blockchain technology" you can probably squint hard enough to do that, see also various "Internet technology" companies from the turn of the century that just consisted of a normal company plus a web site most of which were failures - but I don't think you learn anything from it. And in fact not all of CT is actually finished and deployed. There ought to be a Gossip system, which would allow clients to er, gossip about things they'd learned, and thus discover any inconsistencies which they can't see individually. e.g if from Turkey the log seems to show one entry for this www.google.com certificate but when seen from France the entry is different, Gossip potentially allows a Turkish client to tell a French client what it saw and the alarm is sounded. Gossip is necessary to ensure logs can't deliver a split horizon view and to loop back the trust from SCTs to actual log records, but it's fraught to do this in a privacy-preserving manner. The actual deployed system works for two reasons, which I've no doubt would horrify Blockchain proponents who worship at the altar of distributed consensus: 1. The actors (root Certificate Authorities, trust stores) are basically honest. They're not always competent or diligent or open but they mostly don't deliberately spread falsehoods, so the records in CT would probably be almost as useful even if it was just a huge text file or something with no cryptographic basis of trust. 2. The main clients mandating CT are Safari and Chrome and both of them require that certificates are logged with Google (and somebody else, but you can pick who). So attacks that require falsifying the logs can't work unless Google does them. If you're Google this is enough. If you're not Google it's still pretty satisfying, why would Google build this complicated and relatively expensive system just to lie to me about something I otherwise would have no way to know about in the first place?

tialaramex 6y ago
> (also the M in MD5 and various other things) I should correct this. MD stands for "Message Digest" which is what this type of algorithm is for. So then it's just a coincidence that it's also the initials of (Ralph) Merkle and (Ivan) Damgård whose method for making a cryptographic hash out of a compression function was used.

lucb1e 6y ago

Open site, use the search box on the top right to look for merely the keyword "blockchain", find 1 hit which says: > We are not making "the" blockchain, and we do not claim to support decentralisation. This does not use a blockchain in the bitcoin/ethereum/... sense of the word. Perhaps in a "git" sense of the word, but I don't think that's what OP meant when asking for legitimate uses.