I have no experience in this matter, but it's an interesting problem, so here are my thoughts, whatever they are worth:
When contracting on paper, the signature is a personal characteristic of the signer, so samples can be compared by an expert witness. Unless there's some sort of biometric component to the creation of the certificates, personal characteristics don't enter into crypto signatures, so you need some other way to make it personal, such as a face-to-face meeting at which certificates or at least key fingerprints are exchanged by parties who can sense each other directly, match photo IDs to faces, and the like. You could consider it a keysigning party for two and use published recommendations to guide you in setting up the process. Once personal control is established, I suppose that no more meetings are required. So this would seem to work well for people who are able to meet once, and even better for parties who then make contracts again and again from time to time. If trusted third parties are willing to attest to signatures then the other parties only need to meet with the third parties, separately. I recall seeing notices by some notaries public that they also certify PGP keys. Another form of assurance might be the publication of key fingerprints on the key owner's website. (How much would you bet that your website wasn't cached by Google or sampled by the Wayback Machine before you changed the fingerprint? A number of companies have found, to their embarassment, that trying to "disappear" inconvenient pages is not reliable.) Still another form of assurance would be the publication of keys in the keyserver network, since it's impossible to remove keys unless you control all of the servers. And again, someone may have a copy of that certificate which is simply not remotely accessible but which could conceivably turn up in court. As with signatures on paper, you need to evaluate your risk and decide whether it's acceptable. Your insurance agent may be able to help. If you read some of the laws governing admissibility of digital signatures, you may find that your requirements are already laid out for you, to some level of abstraction. It's a possible starting point, at any rate. And your lawyer might be a good source of pointers to procedural and technical recommendations, since that would make his job easier. I'll note that there are a number of companies in the business of issuing durable digital identity tokens: X.509 certificates. You might want to insist on EV certificates, since EV has a documented meaning and some CAs are not very energetic in identifying non-EV customers. In any case you probably ought to read the CA's Certification Practice Statement and decide whether their procedures are acceptable to you. There may be sound ways to use X.509 material to initialize OpenPGP exchanges if that's important to you, or you could use PEM instead of PGP. -- Mark H. Wood, Lead System Programmer [email protected] Asking whether markets are efficient is like asking whether people are smart.
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