Government Communications Headquarters
The second job of GCHQ is to crack the cyphers (codes) of sources it is interested in. It is this part of the work which Bletchley Park used to do. It also arranges for our own secret transmissions to be coded securely. This is the world of cryptography, ways and means of getting into other people's secrets, and keeping our secrets secure. This is done by CESG (Communications-Electronics Security Group).