Security of andrew.cmu.edu anon-server?

What kind of encryption is the anonymous contact system at andrew using? I think someone said that it used a home-brew cipher. How secure might such a system be against cryptanalysis (or just brute force key searches?) Or has it been changed to use something like DES or IDEA? (In the former case, DES, it might not be completely secure, unless you used 3DES or something.) If someone could break the code, they could find out _EVERYONE'S_ mail address that ever posted using an anon address from that remailer...