Problems with Bruce Schneier's "Solitaire" describes a bias in the output of the card cipher "Solitaire". Here I'll try and describe an alternative cipher of my own design, "Mirdek", that avoids these problems.
Updated 2001.04.07: Hello to visitors from EAWorlds! I notice from my referrer log that a message on this page (scroll down) is bringing lots of hits to this page. Please feel free to mail me with any questions this stuff raises. Note that the "Solitaire" cipher is the one linked above; this page is about my own (so far unsuccessful) attempts to design a secure alternative.
Now, would someone mind telling me what the hell "Majestic" is about? :-)
Updated 2000.01.27: This cipher is not secure: it's terrifically weak against a chosen plaintext attack. I hope to detail these weaknesses in a future revision of these pages, and hopefully propose a stronger variant.
Updated 2000.01.13: I've made many changes since the original version was published here which I hope are improvements. They certainly make the cipher easier to remember and to operate, but I hope that they also improve security. Be warned that there may yet be further changes - this is still a "work in progress".
Mirdek is intended to fulfill exactly the same goals as Bruce Schneier's card cipher Solitaire: a cipher that can be operated entirely by hand, but that resists machine cryptanalysis even from very well-funded adversaries. See John Savard's proposal for another example.