As others have mentioned. One-time pads are unbreakable: "While he was at Bell Labs, Shannon proved that the cryptographic one-time pad is unbreakable in his c

As others have mentioned. One-time pads are unbreakable: "While he was at Bell Labs, Shannon proved that the cryptographic one-time pad is unbreakable in his classified research that was later published in October 1949" - http://en.wikipedia.org/wiki/Claude_Shannon http://en.wikipedia.org/wiki/Claude_Shannon They can also be made to decrypt to any plaintext string http://16s.us/FreeOTP/nsa/ http://16s.us/FreeOTP/nsa/ However, OTP does not scale to more than two or three people, they don't work at all on very large messages as the key has to be as large as the message and they have authentication issues. For two people sending small messages, one-time pads are ideal and if the pads are created, used and destroyed correctly, the encryption is, indeed, unbreakable.