CESG is the Information Assurance (IA) arm of GCHQ and is based in Cheltenham, Gloucestershire, UK. It is the UK Government's National Technical Authority for IA, responsible for enabling secure and trusted knowledge sharing to help customers achieve their business aims.
CESG aims to protect and promote the vital interests of the UK by providing advice and assistance on the security of communications and electronic data. CESG deliver information assurance policy, services and advice that government and other customers need to protect vital information services.