Heh. His password was a chess move!
[Leah Neukirchen] Somewhere around 2014 I found an /etc/passwd file in some dumps of the BSD 3 source tree, containing passwords of all the old timers such as Dennis Ritchie, Ken Thompson, Brian W. Kernighan, Steve Bourne and Bill Joy.
However, kens password eluded my cracking endeavor. Even an exhaustive search over all lower-case letters and digits took several days (back in 2014) and yielded no result. Since the algorithm was developed by Ken Thompson and Robert Morris, I wondered what’s up there. I also realized, that, compared to other password hashing schemes (such as NTLM), crypt(3) turns out to be quite a bit slower to crack (and perhaps was also less optimized).
Finally, today this secret was resolved by Nigel Williams:
From: Nigel Williams [email protected]
Subject: Re: [TUHS] Recovered /etc/passwd files
ken is done:
took 4+ days on an AMD Radeon Vega64 running hashcat at about 930MH/s
during that time (those familiar know the hash-rate fluctuates and
slows down towards the end).
This is a chess move in descriptive notation, and the beginning of many common openings. It fits very well to Ken Thompson’s background in computer chess.