Cryptanalysis of the Enigma Bletchley Park to describe the network that used the same Enigma setting sheets. Initially these were recorded using coloured pencils and were given the names "red", "light blue" etc., and later the names of birds such as "kestrel". During World War II the settings for most networks lasted for 24 hours, although towards the end of the war, some were changed more frequently. The sheets had columns specifying, for each day of the month, the rotors to be used and their positions, the ring positions and the plugboard connections. For security, the dates were in reverse chronological order down the
Cryptanalysis of the Enigma current on the way out to the lamp panel. To decipher German military Enigma messages, the following information would need to be known. Logical structure of the machine (unchanging) Internal settings (usually changed less frequently than external settings) External settings (usually changed more frequently than internal settings) Discovering the logical structure of the machine may be called "breaking" it, a one-off process except when changes or additions were made to the machines. Finding the internal and external settings for one or more messages may be called "solving" - although breaking is often used for this process as well. The various