Many years ago, (the old) SCO released the source for some “ancient” versions of Unix. They did that by releasing a tape dump of the file system. Included in the image was a copy of the password file. The file is from System 3 and well before the introduction of the shadow password file so it had the password hashes in them. The hash was several iterations of DES with some changes to the S-boxes to prevent using hardware to crack them.
From time-to-time people have tried their hand at cracking those passwords just for fun. The DES algorithm is notoriously weak (because of the small key space) given today’s computers so this wasn’t too difficult. One password that no one seemed able to crack was Ken Thompson’s.
For the last week or so I’ve been following a thread on the TUHS mailing list about efforts to find out what that password was. As Leah Neukirchen reports in this blog post, Nigel Williams finally succeeded in cracking his password. It’s p/q2-q4!, which, appropriately enough for Thompson, is an opening chess move.
Looking at it, you can see why it was harder to crack than some of the rest. Whether by design or as a consequence of its being a chess move, it was as hard to crack as it was possible to make passwords in those days. It’s the maximum length and comprises letters, numbers, and symbols. It’s not clear whether or not capital letters were available.
After the result was announced, Thompson posted his congratulations.