Chinese boffins provoke Oz speed camera kerfuffle

Case binned after image algorithm cracked

By Lester Haines • Get more from this author

Posted in Bootnotes, 11th August 2005 11:10 GMT

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Chinese scientists are the unlikely heroes of a New South Wales speeding case which saw a Sydney magistrate dismiss the charge against an alleged speed merchant because the Roads and Traffic Authority (RTA) could not prove that its vital photographic evidence was "secure", news.com.au reports.

At the centre of the brouhaha lies the MD5 algorithm, used to "store the time, date, place, numberplate and speed of cars caught on camera", as smh.com.au explains.

MD5 is intended to safeguard against tampering with this information by turning it into a 128-bit sequence of digits. However, the chaps from the China's Shandong University proved it was possible to alter the data and retain the same code, ie, the RTA could theoretically change, for example, the car's speed without any evidence of tampering.

The whole thing came to a head when lawyer Denis Miralis used this possible abuse against the RTA in the case of a man allegedly caught speeding in a school zone last November. In June, Magistrate Lawrence Lawson gave the RTA eight weeks to produce an expert willing to testify that the photos had not been doctored. When the RTA failed, Lawson threw out the case and awarded the defendant AU$3,300 costs.

Miralis immediately demanded an enquiry into all NSW's 110 speed cameras, declaring: "The integrity of all speed camera offences has been thrown into serious doubt and it appears that the RTA is unable to prove any contested speed camera matter because of a lack of admissible evidence."

Unsurprisingly, the NSW Law Society admitted the judgment might "open the doors for other drivers caught by speed cameras to mount the same defence".

As for MD5, encryption expert Nick Ellsmore said: "Since the [Chinese] research came out, we've been recommending that clients move away from MD5 and we've certainly recommended that people don't use it for new applications." ®

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