What does linear cryptanalysis primarily analyze?

Linear cryptanalysis primarily analyzes pairs of plaintext and ciphertext to uncover information about the encryption key used in a cipher. This method exploits linear approximations to the action of a cipher, which suggests that certain relationships may hold between the plaintext bits, ciphertext bits, and key bits. By examining numerous pairs of plaintext and their corresponding ciphertext, linear cryptanalysis can create statistical biases that reveal information about the key, allowing for more efficient decryption than brute-force methods.

The technique focuses on building linear equations that relate the input and output of the cipher. As more data is collected, the analyst can strengthen the statistical significance of these equations, ultimately enabling the recovery of the secret key.