Paper 2025/438

Transmitting Secrets by Transmitting only Plaintext

Abstract

Presenting a novel use of encryption, not for hiding a secret, but for marking letters. Given a 2n letters plaintext, the transmitter encrypts the first n letters with key K1 to generate corresponding n cipherletters, and encrypts the second n letters with key K2 to generate n corresponding cipherletters. The transmitter sends the 2n cipherletters along with the keys, K1 and K2 The recipient (and any interceptor) will readily decrypt the 2n cipherletters to the original plaintext. This makes the above procedure equivalent to sending out the plaintext. So why bother? When decrypting the 2n cipherletters one will make a note of how the letters that were encrypted with K1 are mixed with the letters encrypted with K2 while keeping the original order of the letters encrypted with each key. There are 2^n possible mixings. Which means that the choice of mixing order can deliver a secret message, S, comprising n bits. So while on the surface a given plaintext is sent out from transmitter to recipient, this plaintext hides a secret. Imagine a text messaging platform that uses this protocol. An adversary will not know which plain innocent message harbors a secret message. This allows residents of cyberspace to communicate secrets without exposing the fact that they communicated a secret. Expect a big impact on the level of cyberspace privacy.