Lorenz Cipher

A stream cipher, manufactured by C. Lorenz AG, that encrypts a Baudot-coded plaintext bit stream into 5 ciphertext bit streams.

Encryption XORs the 5-bit Baudot code with a 5-bit random sequence, generated by 12 shift registers in 3 groups:

• 5 $\chi$ registers, lengths 41, 31, 29, 26, 23.
• 5 $\psi$ registers, lengths 43, 47, 51, 53, 59.
• 2 $\mu$ registers, lengths 61, 37.

At each clock tick $t$:

• $K = (\chi_i \oplus \psi_i)$ for $i = 1, \dots, 5$.
• $t \leftarrow t + 1$, and the $\chi$ registers advance.
• $\mu^{(1)}$ advances every tick, and conditionally triggers $\mu^{(2)}$ to advance.
• $\mu^{(2)}$ conditionally triggers the $\psi$ registers to advance.
• Output $K$.

Key space: