Unshared secret key cryptography: Achieving Shannon´s ideal secrecy and perfect secrecy

In cryptography, a shared secret key is normally mandatory to encrypt the confidential message. In this work, we propose the unshared secret key (USK) cryptosystem. Inspired by the artificial noise (AN) technique, we align a one-time pad (OTP) secret key within the null space of a multiple-output multiple-input (MIMO) channel between transmitter and legitimate receiver, so that the OTP is not needed by the legitimate receiver to decipher, while it is fully affecting the eavesdropper´s ability to decipher the confidential message. We show that the USK cryptosystem guarantees Shannon´s ideal secrecy and perfect secrecy, if an infinite lattice input alphabet is used.