A 17-year-old Kent schoolboy has spent just four weeks putting together an encryption method for computer files which could take 30 billion years to crack.

Peter Parkinson's Unbreakable Encryption program is now available over the Internet and illustrates the futility of many governments' attempts to control the use of the technology.

The United States bars the export of such strong encryption without "key recovery", the ability of a third party to unlock and decode encrypted files if, for example, they suspect criminal activity.

The UK Government also wants such keys, to be held by "trusted third parties", so that the security forces can foil paedophile rings, drug dealers and spies, among others.

Cracked it

But an English sixth former appears to have demonstrated the ease with which strong encryption without key recovery can be programmed and distributed.

His key length is 2048 bits, compared to the 40-bit "weak" encryption allowed for export by the US.

Peter says the maths means it should take 30 billion years to crack. A powerful computer built by the Electronic Frontier Foundation recently took three days to crack the American 56-bit Data Encryption Standard (DES).

The popular Pretty Good Privacy program advertises its 128-bit minimum key length as "the strongest encryption available."

Peter admits 2048-bit encryption is more than anybody needs, but it helps to sell the product.

He designed a slick Windows interface for his program and spent four weeks of after-school and weekend work putting an extra step in the encryption of each bit of the RC4 algorithm, a stream cipher technology developed by America's RSA Data Security.

Good maths not required

"I'm not really very good at maths, I got a B in the GCSE," he said. "But this has to be done by a programmer, though they say it's good if you have a basis in maths."

The program was first released under his own name, CIPHERTech, four months ago. But a US-based online software sales company, Atlantic Coast, has since snapped it up, paying Peter a lump sum rather than a commission on sales.

"Now I'm programming an accounts package for them called Fastcheck. I would like to carry on working with them, they keep phoning me up with little projects."

Peter operates out of his bedroom at home in Maidstone, Kent, and plans to set up a registered company when he is 18, although he still wants to continue his education.

"I'm taking Further Maths, Physics and Geography and would like to go to university to study Geography, not to fart around with computers.