Signals intelligence and information security have a long and honourable history in the service of the Australian Government and its allies in times of peace, crisis and conflict. The current generation of Australia's Sigint and Infosec professionals are proud to inherit that record, and to add their own contributions to it.

But it is a history little known to the public at large. Because of the secrecy that surrounds the business of intelligence collection, many of the great successes of Sigint cannot be revealed until many years later.

Some important aspects of Sigint's history have been declassified. Many readers will be familiar with the story of how the Allied cryptanalysts broke the allegedly 'unbreakable' Enigma cypher system used by the Germans during WWII – a feat that contributed in no small measure to the ultimate Allied victory. It was not until several decades after the War that it was safe to reveal the the full story of Enigma.

More recently, in the mid-1990's, the US Sigint organisation, the National Security Agency, made the decision to release much of the material collected from Soviet diplomatic and intelligence targets during the 1940's, 1950's and later under an operation codenamed Venona.

The Archives Act 1983 contains some special provisions relating to intelligence agencies, including DSD. DSD continues to hold records that would otherwise be subject to public release after 30 years. It does so on the basis that release of this material would compromise ongoing national security interests, or Australia's obligation to protect the material that other countries have provided to us in confidence. In conjunction with National Archives of Australia, DSD has an active program to review this material, with a view to eventual public release.

But, inevitably, there will be many stories that cannot yet be told.