History of Information Assurance (IA)
The New Zealand Government recognised the need to protect its communications early in its Colonial history. Whether it was to diplomatic posts or to military forces, some means had been necessary to ensure that sensitive messages could not be read by third parties.
Secure Book Cyphers
In the period before World War II, New Zealand's military forces and government departments used secure book cyphers. In 1929 the British High Commission loaned copies of the Colonial Cypher to the Department of External Affairs for confidential dispatches between Wellington and Samoa. In February 1937 an Administrative Code and Cypher was introduced and operators were also being trained to use the Government Telegraph Code and the Interdepartmental Cypher.
In 1939 a committee decided that Government (non-military) telegrams would use either the Dominions Office Cypher "... which is moderately secure ..." or the Interdepartmental Cypher "... which is absolutely secure".
According to David Kahn in his book Codebreakers, the Playfair code was first demonstrated in 1854. From February 1941 the New Zealand War Cabinet approved the use of Playfair to secure commercial messages sent by wireless between New Zealand, the Chatham Islands and the Pacific Islands. At this time the use of commercial codes such as the Government Telegraph Code was cancelled and smaller Pacific Islands which did not hold code books were instructed to use their native language. The Playfair code was withdrawn from use in September 1945.
The Playfair code was replaced by the more secure one-time letter code. The Navy view was that the radio transmitters in use at Wellington, Chathams, Niue, Rarotonga, Apia and the Kermadecs were of sufficient power for their transmissions to be picked up in Japan and that the transmitters at outstations working to Apia and Rarotonga were not. Consequently, both IN and OUT pads of one-time letter code were issued to high-powered stations while low-powered stations received IN pads only.
One-time pads may have been more secure than the Playfair code, but they were time consuming in use and prone to arithmetical error. A Naval staff officer commented "... our coding and cyphering systems seem to be coming more complicated every day".
Machine cypher systems overlapped the use of Playfair and one-time pad systems. Typex cypher equipment was based on the principles of the German 'Enigma' machine with its series of code wheels (see picture). Around 1928 the British were considering replacing their book cypher systems, so the Admiralty purchased two commercial Enigmas. In 1935 the Air Ministry commissioned Creed & Company to manufacture three sets of 'Enigma type' machines. By 1936 Creed had made two devices which became known as the RAF Enigma with Type X attachments and subsequently as 'Typex'.
In 1941 the British government supplied ten Typex machines to New Zealand, 145 being paid for each machine. The NZ Navy made one Typex available to the Prime Minister's Department and by January 1942 Typex communications had been established to the Secretary of State for Dominion Affairs in London.
Typex remained in service in New Zealand until replaced by more modern systems, the last Ministry of Foreign Affairs machines being dumped at sea about 1973.