🚀 go-pugleaf

   In article <YSN9FVS@minnie.zdv.uni-mainz.de> pom@anke.imsd.uni-mainz.DE (Prof. Dr. Klaus Pommerening) writes:
   >[technique for stealing messages if you can get someone to 
   > sign them by decrypting with their public key as an
   > acknowledgement of receipt.]
   >Never sign a document that Charles presents to you!

It was an interesting attack, and demonstrated that there are stupid
ways to use any technique, but the fundamental weakness was that
the protocol assumed that Alice would sign a document without reading it first.

This is just as stupid in the electronic world as it is in the paper world -
Imagine if the post office used registered-mail receipts like
	Pay Charlie $1000000 from my account, signed ____________

The most you would typically use for an delivery-acknowledgement protocol
would be to sign a checksum (MD5 or whatever) or a document,
or more likely to sign a note saying
	I received message with checksum 765765765 at time 14:37
		signed Alice
which doesn't let your attack work.
--
#				Pray for peace;      Bill
# Bill Stewart 908-949-0705 wcs@anchor.att.com AT&T Bell Labs 4M312 Holmdel NJ
# Nov 12 - Anniversary of Indonesian massacre in East Timor, 1991
# Indonesia first invaded in 1975, and about 1/3 of the people have been killed.