Pollux Cipher

The Pollux cipher uses Morse code and a tomogrammic overcipher that replaces the dashes and dots of Morse code with alphanumeric characters.

The plain message is first encoded in Morse, then the 3 Morse symbols (Dot, Dash and Space) are encoded via a predefined correspondence table.

Pollux decryption requires the knowledge of the correspondence between the numeric / alphanumeric characters and the dashes / points / spaces from the Morse code.

The Morse code is reconstructed and can be translated into plain text.

Decoding a Pollux message without a Morse character-to-symbol correspondence table is extremely difficult, but not impossible.

It is possible to use a probabilistic approach called MCMC (Monte Carlo Markov Chain). This method does not attempt to test all possible correspondences (which would be practically impossible), but rather to progressively explore the most likely configurations using a random optimization process.

— Starting from an initial (and often random) correspondence between the ciphertext and the Morse symbols.

— Decode the text according to this correspondence and evaluate the plausibility of the result (letter frequency, consistent words, etc.).

— Modify the correspondence slightly (by swapping a few symbols), re-evaluate the result, and if it is better, keep it; otherwise, try another modification.

By repeating this process thousands of times, the system converges towards the most plausible correspondence and thus towards the plaintext.

dCode applies this method but it does not always guarantee the exact solution (especially if the message is less than a hundred characters and the calculation time is limited), but it often allows to find at least a text close to the original message.

A Pollux encrypted message will have a minimum coincidence index (due to polygrammic encrption and the characters chosen randomly). Cryptanalysis is therefore difficult.

Morse code does not usually have two consecutive spaces, and it is rare to find long sequences of dots or dashes. Also the text should not start with space because the first space character should be in position 2, 3, 4 or even 5.

Any reference to mythology, Dioscuri (Castor and Pollux) is a clue.

Any reference to the Manège Enchanté (French TV series, with Pollux the dog) is a clue.

The Pollux cipher was popularized in some recreational cryptography publications in the 20th century. Its exact authorship remains unknown.