Court case falls apart because of MD5 insecurities

According to a post on the cryptography mailing list, an Australian court threw out a case against an (allegedly) speeding motorist because the speed camera images were secured using MD5. The defence argued that MD5 was a "discredited piece of technology". Indeed, the MD5 hash function was shown to have a weakness last August when a team of Chinese researchers announced that there was a practical method to generate collisions.

But it's not totally clear what's going on here. One possibility is that the speed cameras digitally sign the evidence, or more specifically, the MD5 hash of the evidence. To tamper with the evidence, you'd need to mount a second preimage attack, but, as far as I'm aware, nobody's come up with a way of doing this.

Another possibility is that the camera simply prepends the evidence with the MD5 hash, which provides no integrity guarantees, but that's got nothing to do with the security of MD5 per se.

Still, there's a great quote from the defence lawyer Denis Mirabilis: "People have shown it [the algorithm] has been hacked and it's open to viruses."

Update: Slashdot have just covered this.

Tags: Cryptography , MD5