-----BEGIN PGP SIGNED MESSAGE----- I'm not exactly sure what this thread is about :-) but I do have some numbers: Differential cryptanalysis of DES requires 2^47 = 140737488355328 = 1.4 10^14 known plaintexts. The complexity of a brute force DES attack (keysearch) is 2^56 = 72057594037927936 = 7.2 10^16, or 2^55 = 36028797018963968 = 3.6 10^16 if you are efficient. Similary, brute forcing IDEA is 2^128 = 340282366920938463463374607431768211456 = 3.4 10^38 The best factoring algorithm (gopher plug: check in Misc/ for a recent "bits and difficulty factoring post") for a 1024 bit key is a complexity of 4.42 10^29. Somewhere around 1600 bits comes a point where it is "easier" to attack IDEA than factor the resulting number. Karl Barrus <klbarrus@owlnet.rice.edu> -----BEGIN PGP SIGNATURE----- Version: 2.3a iQCVAgUBLNKNqYOA7OpLWtYzAQFlkwP+PdenJNJOKm9zcxkL4Zaq22aujfa2SAgk 1NILjQzZI8uZe9FIn8p2uEoS3YjYskg40tEMeohhGqZ371s/ndlTjDDhga0PCXLj Q4UHoowTVR9hx/cVGzLhuZbyAwbbqAvygGQNKN1iXn3IqpLoNV3Do+TtUj0xLt1l 0j1gl055YL4= =Vl2r -----END PGP SIGNATURE-----