Hello all, Lets face it the real challenge is DES, but those 56 bits are quite a bit harder than 40. 65536 times harder in fact. But if people broke 48 bits then maybe they might start to see 56 as being in reach. After all everyone wants to be in for the biggie. So before the NSA fobs us off with 48 bits can we crack it? Wind up the 40 bit code a tad and set to work. It sounds as if it is comparable to the RSA-129 prime that was cracked (OK its probably a touch harder but machines are faster now). So who wants to make an RC-48 and a DES challenge? Phill.