Behind the MD5 attack

When the researchers who produced the elegantl MD5 attack I wrote about this morning realized the severity of what they had found, they took two highly unusual steps. First, they consulted with lawyers from the Electronic Frontier Foundation, describing their findings and voicing their concerns about the potential legal ramifications. The researchers were afraid that if the certificate authorities found out about the researchers’ work and its implications for the security of their digital certificates, the CAs would move to stop the researchers’ talk at the 25C3 conference today in Berlin, at the very least, and perhaps sue them for good measure.

Second, the group approached Microsoft and Mozilla, the two dominant browser vendors, and  explained that they had a serious browser security issue that they’d like to share. But first, they needed some assurances from the two vendors that they wouldn’t share what they heard with the CAs before the researchers were ready to announce their findings. So they asked Microsoft and Mozilla officials to sign non-disclosure agreements. It was a 180-degree reversal from the way that these things normally work.

In most cases, researchers who approach a vendor with a security problem are asked by the vendor to keep quiet about the vulnerability until a patch is ready. But in this instance, the researchers held the upper hand and chose not to even tell the vendors what the issue was until they had the signed NDAs in hand. Alex Sotirov, one of the researchers involved in the project, said that it took some negotiations to get Microsoft officials to agree to the NDA, but they eventually signed on. As did Mozilla.

During their presentation in Tuesday, the researchers said that they were hopeful that other researchers would follow their lead. And Dino Dai Zovi, a researcher who was not part of the project but who was briefed on the team’s work, agreed. “A letter from a lawyer is usually enough to stop any researcher,” he said. “But showing up with your own lawyer changes the balance of power.”