Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site gatech.UUCP Path: utzoo!watmath!clyde!akgua!gatech!spaf From: spaf@gatech.UUCP (Gene Spafford) Newsgroups: net.crypt Subject: Re: One-time pads Message-ID: <4050@gatech.UUCP> Date: Sun, 19-Feb-84 19:25:36 EST Article-I.D.: gatech.4050 Posted: Sun Feb 19 19:25:36 1984 Date-Received: Mon, 20-Feb-84 08:52:19 EST References: <2540@azure.UUCP> Organization: The Clouds Project, School of ICS, Georgia Tech Lines: 38 As has been pointed out, it is certainly probable that some run of truly random digits will result in a readable text, but what is read may have no relation to the actual message. In fact, that type of situation is more likely to occur than the case of a string of zeros leaving the text unencrypted (consider how many strings of length N have valid meanings, as opposed to the one "true" meaning). However, suppose you are the person reading the encrypted message. If you see text which happened to be readable and described a recipe for Aunt Pat's oatmeal cookies, you probably would ascribe to the randomness of the encryption. (You might also decide to see if it was a code of some sort (as opposed to cypher)). On the other hand, if you saw something like the formula for a new nerve gas, you'd definitely try to have your chemists put it together and give it a try. Your chances might not be good that it was actually a formula for nerve gas, but if it was, you'd have it. (Actually, with the kind of randomness we all know and love: 1) Aunt Pat's cookies could be more lethal; 2) Aunt Pat's recipe could be encrypted into a valid formula for nerve gas of which the sender never knew!) If I send my password via a one-time code and it gets transformed into some other string of characters, what do you lose by trying that string? Nothing, but there is a very small chance that what you have is a correct password. In fact, with a truly random sequence, and a six bit character code with all bits significant, the probability of finding a six character password unchanged by the encryption is on the order of 1 in 2 ** 36. That's not very good, but it may be enough. However, that kind of probability is usually much more than sufficient for most applications. As an aside, a good story embodying some of the thought in this discussion is "The Library" by Jorge Luis Borges in "Labyrinths." -- Off the Wall of Gene Spafford The Clouds Project, School of ICS, Georgia Tech, Atlanta GA 30332 CSNet: Spaf @ GATech ARPA: Spaf.GATech @ CSNet-Relay uucp: ...!{akgua,allegra,rlgvax,sb1,unmvax,ulysses,ut-sally}!gatech!spaf