Alex Katalov, Russian hacker complete with beard and laptop, had just landed in Paris when we met him. The entrepreneur is in the password recovery business, and he seems rather good at it. Elcomsoft, his company, sells tools to law enforcement, amongst others. Elcomsoft got some legal exposure in 2002, when it published a tool to break Adobe's eBook Reader encryption, allowing users to transfer eBooks to other medias. Today, however, it's back to password recovery business. 

SecurityNewsletter.com : What password-protected document can you recover passwords for ?

Alex Katalov : We can work with ZIP archives, PDF documents, Microsoft Office documents, and even PGP. Of course, the recovery is more or less difficult, or at times impossible, depending on the version of those softwares, the password used and the key's length.

SNL : What's the easiest ?

AK : For ZIP password-protected archives, if there are more than five files in the archive, we can recover the password no matter what. With PDF documents, we can break any 40 bits encryption through rainbow tables. Above, for 128 bits encryption we use brute force, but it gives pretty good results. Last test we did, on 10.000 PDF files encrypted differently, we were able to break 10% of those in less than half a second, 50% in less than 8 seconds, and 99% in 250 seconds. As for Microsoft Office, we can decrypt anything up to Office XP, or above if the documents use Office XP compatible protection. And those are by far the most common.

SNL : What makes it so easy ?

AK : Along with the regular CPU, we now use computing power from Nvidia GPUs if present (only for the 8000 series). It makes the recovery process 10 to 20 times faster on a dual Intel 3ghz (editor's note : a full Windows Vista NTLM password crack could take less than five days). And of course, we take advantage of design flaws.

SNL : How are the vendors responding to you breaking encryption functionalities they develop for their products ?

AK : Well, we are Microsoft Gold certified partner, so not all of them are mad after us. But they sure don't help us in any way !

SNL : What would be your advice to companies wanting to protect their files ?

AK : I'd say use AES whenever it's possible. Also, the two applications we have the greatest difficulties cracking passwords for are PGP and WinRAR. For the later, we can only try 400 passwords per seconds (compared to millions for WinZIP), so any password above 5 characters is rather safe. And the author does not bother with backward compatibilities. If we manage to crack it, he will change it overnight. Other than that, it's the regular advice : use 8 to 10 characters long passwords, with mixed case and punctuation, and change them often. But considering the average user can only remember about 8 different passwords, we still have some good business ahead of us !