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> There's no other model than the web-of-trust. SPKI & SDSI had a different model: rather than trust people to tell you who someone is, one trusts them to tell
by wtbob 12y ago
> There's no other model than the web-of-trust.
SPKI & SDSI had a different model: rather than trust people to tell you who someone is, one trusts them to tell you who they think they are. That is, rather than me verifying that key 0xDEADBEEF belongs to the individual known to the town council of Lower Shroppington as 'William Morris' (which is inherently fragile: I may not be an expert at verifying identity documents, or at verifying those issued by Lower Shroppington; the individual before me might have a document issued by Lower Shroppington deliberately to mislead me; heck, who is the real William Morris: there could be more than one), I would just verify that this is the individual I call William Morris, and let you make use of that as you may. If Lower Shroppington wanted to, they could issue a certificate stating that they call him William Morris too.
It was a really smart way of doing things.
How might it fit into a modern email infrastructure? Easy! example.com could use key 0xBADDA451 use certify that foo@example.com belongs to the keyholder of the key 0xC0FFEEBA; .com could use key 0xFEEDBAC7 to certify that example.com belongs to 0xBADDA451; the root domain could use key 0x55378008 to certify that .com belongs to 0xFEEDBAC7; IANA could certify the ownership of the root domain; the ICANN board could certify the current IANA key; the previous ICANN board could certify the current ICANN board, and so forth.
What would you see in Outlook or Gmail? Your agent would display that the claimed sender email is valid. It might also try to find some path connecting you & good ol' Bill Morris, then show you that your buddy Steve's ex girlfriend Wilhelmina says that key belongs to Billy Morris.
Interestingly, this could even work for an email legitimately sent on William's behalf. All a normal user would care about is, 'this email is legit' (for some value of); us geeks could geek out as we wished.
- tinco 12y agoSo that's the authority model, or the 'tree-of-trust'. In a good trust model I think it can't be more than just a weighting or advisement over your web-of-trust, never your sole source of trust. In the end a tree-of-trust rests on the fact that you trust the manufacturer of your laptop that they put trustworthy certificates there so you could verify the roots. We're seeing the major browsers now turning that tree-of-trust into a web-of-trust by cross referencing domain certificates to see if there are duplicates or other shady things going on.
- wtbob 12y agoPerhaps I didn't explain well. SPKI/SDSI specifically isn't the authority/tree-of-trust model: although it could be used as the infrastructure to build an authoritative, tree-of-trust system, it could also be used as the infrastructure to build a web-of-trust system, and it can be used as the infrastructure to build an even less trust-requiring system. > In the end a tree-of-trust rests on the fact that you trust the manufacturer of your laptop that they put trustworthy certificates there so you could verify the roots. For hostname and IP address ownership, there is a central authority: ICANN. The problem with the CA model is that someone other than ICANN can lie about who owns a hostname. As for the ICANN roots, those should be publicly known and verified in the same way that any information is publicly known and verified (ultimately, it comes down to verification). The problem with ICANN being a central authority is that knowing that I'm talking to the legitimate owner of 'apple.com' tells me nothing. It could be Apple Records or an apple farm or a guy who just really likes Apples for all I know. The CA system uses a ridiculously expensive, painful process to do ICANN's job for it, and still doesn't provide me the guarantees I need in order to do business online. With respect to email, I can use a tree-of-trust system to guarantee that I can send email to the legitimate owner of an email account, but I cannot guarantee that said legitimate owner is the person I think it is (after all, ICANN in a very real sense owns the Internet, and could transfer anything to anyone). If I wish to, I could use an SPKI/SDSI system to ensure that I'm sending a message to the person who the person who the person who I think is Jim thinks is Sally thinks is Bill. Which, really, is the only way trust can work anyway. What does anyone know other than what he has heard from others?