Common-Key Cryptosystem with Mixture of Fake Plaintexts

One of the fundamental methods for eavesdroppers to achieve a plaintext from a cryptogram is the brute force attack where possible candidates of decryption keys are exhaustively applied to the decryption algorithm. Here the only reason why the eavesdroppers believe to find the common-key and to achieve the plaintext is that the output of the decryption algorithm is contextually acceptable. According to this fact, this paper proposes a novel common-key cryptosystem where fake plaintexts which are also contextually acceptable are mixed into a cryptogram with the legal plaintext. If an eavesdropper applies a fake common-key to the decryption algorithm, it outputs the fake plaintexts which the eavesdroppers might believe legal. This paper also proposes concrete encryption/decryption algorithm which can be combined with any conventional common-key cryptosystem. Keywords—cryptography; common key cryptosystem; fake plaintexts; brute force attack