CA Exploit Update: Falling Sky Averted

By Marc Handelman on January 2nd, 2009

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In an update to the recent Certificate Authority attack research revealed at the CCC last week, ZDNet’s ZeroDay Guest Blogger Jon Viega has posted a tremendous raison d’être to not fear the end of the interwebs…A short snippet of his post (along with appropriate URLs) appears after the jump. You may also wish to visit Rational Survivability, for a slightly different (as in Hoffian) perspective to this issue…

From ZDNet’s ZeroDay Guest Blogger Jon Viega’s Post: “Today there’s been a lot of buzz about the clever new attack on public key infrastructure from Alex Sotirov and a team of researchers. In the attack, the bad guy ends up with his own Certification Authority (CA) that is fully trusted according to every major browser. People are declaring the entire Internet is broken, and that it will be hard to fix. This is simply not true.

The major misconception I’m seeing over and over is that the problem allows the bad guy to steal the signature off any valid MD5 signature from any certificate on the Internet.

Actually, the attack works by a bad guy generating two certificates, one that is just a regular web site certificate, and the other that is a CA certificate. Then, to get the CA certificate trusted, the bad guy submits the web site cert. If he can predict the internal values the CA will use when he starts generating the certificate (a process that takes a few days right now), then he will get back a signature that can be pasted onto the CA cert. That allows the CA to generate new certs to impersonate anybody on the Internet (e.g., Citibank.com).—-