The Enigma Patent

Patent number GB267472 was published on 11th September 1927 as granted to Chiffriermaschinen AG for 'Improvements in and relating to ciphering machines'. In particular, it makes 7 claims relating to the nature of the rotating ciphering drums. There were two related patents, GB231502 (filed 1926) and GB343146 (filed 1928).

The machines were offered to the British government on a commercial basis in June 1924, and later the focus of much activity at Bletchley Park.

Refer to Public Record Office disclosures HW25/6 to 16, The Daily Telegraph's 'Key to breaking Nazi code was in the patent office', Cryptologia's 'The commercial enigma: beginnings of machine cryptography, The German Enigma Cipher Machine - History of Solving and The Enigma rotor-type ciphering machine.