Flame Extinguished?

I will give Microsoft credit in reacting quickly to Flame and its use of faked Microsoft CA certificates. Microsoft quickly came out and moved the two MD5 certificates that were faked and the SHA1 certificate that was abused to its untrusted store. The fact that they did this through the Microsoft update, which was one of the transaction sets that was hijacked by these certs, is kind of funny but that is an aside.

So did Microsoft solve the problem. The simple answer is NO!

Microsoft solved the problem that was created by their certificates. The problem that was created by generating a CA certificate and having the signature applied using an algorithm that was known to have weaknesses and was demonstrated to be attacked in a very similar way the year BEFORE the certificate was generated. In putting their certs in the untrusted store they closed this door - but this is not the only door that exists.

What Flame did was highlight that this attack is not only feasible but something that is executable. Did this take a high degree of knowledge and expertise - of course. The MD5 attack was a bit different then that demonstrated in the past - but this was something that was going to happen. The original demonstration of an MD5 collision attack was done on a cluster of high-end IBM UNIX servers. A few short years later the attack was performed on a network of 200 Playstation 3s. Now this says a lot about technological advancement in processing power for sure but also says a lot about the threat and how rapidly it grows. In 2005 when this was an active topic Ron Rivest (the R of RSA) said ""md5 and sha1 are both clearly broken", when speaking in terms of collision resistance. 


So what do we take away from this? Organizations, including groups like the CA Browser Forum, need to get very diligent about what CA certificates are in browsers, applications, and hardware devices. These need to be assessed for requirement, strength and validity periods and a clear strategy needs to be put in place to understand what is there and how to replace what should not be there. If you look in your out-of-the-box browser today you will not only find MD5 based signatures but also MD2 based signatures. Yes these have been around for some time but we must think that if they have been replaced with a new infrastructure why are we keeping the old ones around? We must also start to question the lifetime of the SHA1 based signatures. There are some CA certificates that are out there that are SHA1 with very long lifetimes - and some with weak key algorithms (RSA-1024 keys for example).


So it is time to get diligent and start to manage your environments - or the next flame may be one licking at your feet.