Codebook Attack

Related Concepts

Block Ciphers

Definition

A codebook attack is an example of a known plaintext attack scenario in which the attacker is given access to a set of plaintexts and their corresponding encryptions (for a fixed key): (P _i ,  C _i ), i = 1, …, N. These pairs constitute a codebook which someone could use to listen to further communication and which could help him or her to partially decrypt the future messages even without the knowledge of the secret key. He or she could also use this knowledge in a replay attack by replacing blocks in the communication or by constructing meaningful messages from the blocks of the codebook.

Applications

Codebook attack may even be applied in a passive traffic analysis scenario, i.e., as a ciphertext-only attack, which would start with frequency analysis of the received blocks and attempts to guess their meaning. Ciphers with small block size are vulnerable to the Codebook attack, especially if used in the simplest Electronic Codebook mode of...