Thanks to everybody for their interesting contributions to the partial signature problem. Anonymous <anon@anon.efga.org> writes:
A more general approach calculates the document hash in a line oriented way. Normally we start at the top and work down through the document to get the hash, which is signed. Instead, we would calculate a hash for each line of the document separately, and then combine them using a tree.
This approach looks like the best to me. It's a bit cumbersome for the person doing the quoting, but that's as it should be. Brian B. Riley writes:
I haven't been follwing this thread that closely, but skimming mch of it and then rereading this whole post, I must concur that the context issue renders much of the discussion moot unless you can not only relate individual sub-blocks to the whole message it came from in the proper order ... it seems to me we are right back where we started, quoting referenced message(s) in entirety.
It occurrs to me that if an issue is important enough that the veracity and autheticity of a given passage is that critical, including entire messages is of trivial concern. Now it could be handled by the discussion participant quoting out of context and 'footnoting' his quote with a message ID. The message corresponding to that ID has its entire text is signed and publicly stored and accessible. If it needs to be checked then go check it, if not take it on faith and read on.
It's easy to see why we would want other people to sign with signatures which enable partial quoting, but it's less clear why we would sign our own messages this way. For instance, somebody might want to quote my private e-mail out of context where I say "Yes, I'm real glad I got rid of that guy. He was really a pest." But they might not want to quote the part of the message where I say "Thanks for the latest shipment of plastic explosives." In order to authenticate their claim they have to reveal the entire message. If they must quote the entire message for authentication, it will discourage tacky behavior such as relaying private messages. So, this is sort of a solution looking for an application. It seems like an interesting problem and I have a strong intuitive sense that a use for it will present itself at some point. Monty Cantsin Editor in Chief Smile Magazine http://www.neoism.org/squares/smile_index.html http://www.neoism.org/squares/cantsin_10.htm Subject: Re: Quoting Portions of a Signed Document To: cypherpunks@algebra.com 16A5942B6EED349ECF4594C784DFD177 [Cantsin Protocol No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