自己实现的一套des算法，速度还可以，C++做的，以前实验的代码，速度在1M左右-Own implementation of a set of des algorithm, the speed can, C++ to do, before the test code, the rate of about 1M

Weakest link” is size of key Attacks take advantage of encryption speed 1993: Weiner: $1M machine, 3.5 hours 1998: EFF’s Deep Crack: $250,000 92 billion keys per second 4 days on average 1999: distributed.net: 23 hours OK for some things