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It would be neat if you could quote people and prove that they signed the particular paragraph quoted without supplying the entire text. Is there a way to do this? (It seems impossible, but so does mental poker.)
A crude approach would be to sign every paragraph or line separately, but that's obviously inelegant.
Well this could be done by creating a document signature and then a collection of sub signatures but it can get ugly real quick.
Ugly's the word for it, alright. ;-)
What level of granularity does one use for the sub signature?
It would be nifty if there was a way to show that any continuous set of bits were signed given only one signature on a whole document. Intuitively, it seems to me that this might be provably inconsistent with a secure hash. Still, crypto results are full of surprises, so I could imagine there is a way to do this.
Then what does the sub signature really tell you? Yes you can verify that the quote was written by someone but it may be taken completely out of context.
Good point. It is nice that people who quote out of context now in a misleading way are convicted when you demand proof. Still, my sense is that this would be a pretty useful thing to be able to do and it would be technically interesting. For example, you might want to reveal parts of a message signed by somebody else without revealing the entire message. Monty Cantsin Editor in Chief Smile Magazine http://www.neoism.org/squares/smile_index.html http://www.neoism.org/squares/cantsin_10.htm -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQEVAwUBNHtvB5aWtjSmRH/5AQEFvgf8C2gv6G9XZjAjfYy6+wtNY0n/3k8TZXj7 Yr0x9jidiJvfRXOi6cjKskmQ8WL98EbVkjHZkPN2t7rlLtLfQVQyQhBtW0jeXlav dC9tSbNO9ThpIAlztO4Wfpx75xNHgEyvMAMB0CnGj1ZcmgParL6F/WM9nkhaI+ZT R8Uu53BZXsCz408/YI4yu4t6E3SXhOJQYFjQ/JxaI8G9mTBpXXbNV9PoN4i2PjHe 0VfOeU0IAJNvWazFqbwcnTuDpcFvQRY70FhgR1exb7MzPYqJMm7D5kdUtZqFWLAH RkwjusDo01rE6+1YxPtq8dP4/8I1wEUsNLOtLyG9gQ2CT+xBhXfrDw== =FT0Y -----END PGP SIGNATURE-----