On Thu, 5 Sep 2013 23:24:54 -0400 Jerry Leichter <leich...@lrw.com> wrote: > They want to buy COTS because it's much cheap, and COTS is based on > standards. So they have two contradictory constraints: They want > the stuff they buy secure, but they want to be able to break in to > exactly the same stuff when anyone else buys it. The time-honored > way to do that is to embed some secret in the design of the > system. NSA, knowing the secret, can break in; no one else can. > There have been claims in this direction since NSA changed the > S-boxes in DES. For DES, we now know that was to protect against > differential cryptanalysis. No one's ever shown a really > convincing case of such an embedded secret hack being done ... but > now if you claim it can't happen,
It is probably very difficult, possibly impossible in practice, to backdoor a symmetric cipher. For evidence, I direct you to this old paper by Blaze, Feigenbaum and Leighton: http://www.crypto.com/papers/mkcs.pdf Perry -- Perry E. Metzger pe...@piermont.com _______________________________________________ The cryptography mailing list cryptography@metzdowd.com http://www.metzdowd.com/mailman/listinfo/cryptography
