Zimmermann plays down PGP flaw

And sticks it to Czech discoverers

By Kieren McCarthy, 22nd March 2001

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Phil Zimmermann - creator of the OpenPGP encryption software - is playing down a flaw discovered in his hugely popular program, saying that someone would still need access to your hard drive to break the code.

Two Czech researchers, working for their country's National Security Authority, claimed to have found a way to bypass the public/private key system. The claim was posted on a Czech IT company's Web site. They refused to give any details, however, leading many to believe it was a hoax.

Zimmermann and Network Associates - which owns the PGP trademark - subsequently announced that the flaw was real, but assured all that it does not compromise the system. They also criticised the Web site - ICZ Group - for failing to give it any technical details and using the news as a publicity stunt on the eve of CeBIT.

The flaw, according to ICZ's press release, allows someone to find out a person's private key by modifying the encrypted key and then getting hold of a message signed with that key. A small program can then work out what the private key is. You can then use it to pass off future messages as coming from that person.

Zimmermann said this is not a practical way to steal keys however. "Your adversary has to be able to modify your private key," he said. "That means they have to have access to your computer." Only then could they install software to monitor keys and/or passwords. The implication is that if someone has access to your computer they can do pretty much what they want anyway.

As for his and Network Associates' claims of publicity seeking, ICZ is certainly milking the situation for all its worth. Its front page contains little else. It has now put an Acrobat file on the flaw on its site as well as an FAQ and some media reports.

In its FAQ, it answers the question: Why have you made your attack public? thus: "Because it is momentous finding, which on the theoretical level concerns many electronic signature systems around the whole world, not just programmes based on the OpenPGP format. It is necessary to distinguish the theoretical benefit and the hunt for sensation of the type 'they breached the electronic signature'. It would be the same as if we found that a car's braking system has serious construction flaws. It is our job to inform the public about it, even if we physically tested the fact in only one type of car which uses it."

PGP (pretty good privacy, if you didn't know) is currently used by about 10 million people but is expected to take off in the next couple of years as it becomes accepted by business as a legally binding signature. ®