On Tue, 08 Jul 2003 15:31:08 GMT, John P. Willis <jwillis(a)coherent-logic.com> wrote: Such a thing exists, it is called a one-time pad. Generate a completely random key as long as the plaintext, and then XOR each successive bit of the key with the corresponding bit of the plaintext. The result is indistinguishable from random noise; only someone with an identical copy of the key can decrypt it (using precisely the same method of course). Assuming you mean "one character of encrypted data might represent any one of several different characters of plaintext" (not "one character's worth of encrypted data represents multiple characters worth of plaintext), this is indeed the effect of a one-time pad. Just don't ever reuse that key; promptly destroy both copies after use. --Mirian