THE US government has closed a three year investigation into the export of the Pretty Good Privacy (PGP) encryption program.
The inquiry into the programwritten by software engineer Philip Zimmermann involved a US law banning the export of strong encryption technology.
PGP is regarded as very robust and it is available worldwide on the Internet.
Zimmermann's lawyer, Philip Dubois, said PGP was never exported by his client intentionally but that he "gave it to friends" to promote his belief in the right to privacy. "It was a political statement ... He wanted people to have it and pass it around."
William Keane, an assistant US attorney in San Jose, California, did not say why the government had closed its investigation. But he emphasised that there was no change in the law. "If you're planning on making encryption available over the Internet . . . or other means, better check with the State Department first."
Zimmermann, who had been facing a grand jury investigation and the possibility of a felony charge and severe penalties, said the government's decision "means that I can get on with my life."
The cryptographer, based in Boulder, Colorado, said he would continue to advocate the right to privacy, adding that a new PGP version designed to encode telephone conversations that take place via computer was made available last week to an organisation in Massachusetts that makes PGP available within the US.
Zimmermann finished writing PGP in mid 1991 and it quickly spread over the Internet. It uses a powerful method known as public key encryption, in which a user generates two electronic keys using the program.
The "public" key is posted freely on the Internet. Anyone wanting to send a message to that user can encrypt it with the public key. The message can only be decoded with the user's "private key" which is kept secret.
PGP also allows digital signatures to be added to electronic documents that are not encrypted, so that the recipient knows the e mail has not been tampered with. The signature also proves that the message was generated using the sender's private key, so the sender cannot deny having sent the message.