The Irish government unwittingly purchased and operated encryption equipment from a company secretly owned by the CIA in the 1980s, according to classified documents.

The equipment gave the American intelligence agency, and consequently the British government, access to most encrypted messages sent and received by the Irish government from officials abroad during the sensitive period leading up to the 1985 Anglo-Irish agreement.

According to a detailed report in The Washington Post on Tuesday, citing a classified CIA internal history, Ireland was one of 62 named countries which purchased equipment from Crypto AG, a company wholly owned by the CIA and West German Intelligence (BND) and operated as a joint intelligence-gathering venture.

Security sources confirmed to The Irish Times the government purchased an encryption device and accompanying manuals for more than £900,000 (€1.07 million) in the early 80s to allow it to securely communicate with its embassies and officials abroad.

The CIA’s knowledge of the inner workings of Crypto AG equipment allowed it to easily intercept and decode diplomatic cables, the documents stated.

They do not detail what intelligence was gathered from Ireland or how it was used. However, they state the CIA was happy to share intelligence gathered from other Crypto AG users, such as Argentina, with its British counterparts.

In the Irish case this would have included sensitive information about the government position on Northern Ireland as it attempted to negotiate a greater role in its affairs in mid-1980s.

In line with its standard security policy, the Department of Foreign Affairs yesterday refused to comment on the matter, including on when or if the government stopped using the machine.

Many countries stopped using the devices with the arrival of online encryption methods, although the documents indicate the CIA operation is still live.

Security expert and retired deputy director of Irish Military Intelligence Michael Murphy said the revelations should not come as much of a surprise.

“Small states like ours, who don’t develop their own encryption equipment and have to buy it in, must assume someone else is always listening,” he said.