-----BEGIN PGP SIGNED MESSAGE----- In <199711260002.BAA28863@basement.replay.com>, on 11/25/97 at 07:02 PM, nobody@REPLAY.COM (Anonymous) said:
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.
Well you can do it. Wether you want to do it is another matter. For the level of granularity you are sugesting a hash is not pratical. You could just use RSA encryption to encrypt the message in the following manner: The user encrypts the message with his *private* key. Rather than encrypting the entire document in one operation he would encrypt each [insert you level of granularity here] and then concantinate the results. Say we wanted a level of granularity of a word: word1 word2 word3 word4 the resulting cypher text would be: cypher1 cypher2 cypher3 cypher4 Now if someone wished to verifiably quote words 1,3,4 they would include cypher1 cypher3 cypher4 in their document. Since cypher 1,3,4 could only be generated by original author it can be verified that he actually wrote those words. At a bare minimum this would have to be done on a level of granularity of a sentance to have any meaning at all and even then it's relavance would be questioned. - -- - --------------------------------------------------------------- William H. Geiger III http://users.invweb.net/~whgiii Geiger Consulting Cooking With Warp 4.0 Author of E-Secure - PGP Front End for MR/2 Ice PGP & MR/2 the only way for secure e-mail. OS/2 PGP 2.6.3a at: http://users.invweb.net/~whgiii/pgpmr2.html - --------------------------------------------------------------- -----BEGIN PGP SIGNATURE----- Version: 2.6.3a Charset: cp850 Comment: Registered_User_E-Secure_v1.1b1_ES000000 iQCVAwUBNHt00o9Co1n+aLhhAQHrKwP/SfQYrH07AA1WxJa/atnYfrnlkORgsevK eO0EDDBcz3XIwBWP43y1l8XqRcK0F5sLjdQ6L0s8t9CmqH4N00awfM8UlN7bm69s 9AGuJwA1/UanfOi6TDXclvKJYgMCRerP0X+Yvr04gePObITYOrMKZUbDdYnO/70Y 2EpPAbaPcg4= =5HsX -----END PGP SIGNATURE-----