密码算法md5 c源码

代码说明：

1. 对信息进行填充，使其字节长度与448模512同余 2. 设置好4个链接变量，进入算法的4轮循环运算 3. 每轮一个非线性函数 F(x, y, z)  (((x) & (y)) | ((~x) & (z)))   G(x, y, z)  (((x) & (z)) | ((y) & (~z))) H(x, y, z)  ((x) ^ (y) ^ (z)) I(x, y, z)  ((y) ^ ((x) | (~z))) MD5轮主要操作: FF(a, b, c, d, x, s, ac) { (a) += F ((b), (c), (d)) + (x) + ac; (a) = ROTATE_LEFT ((a), (s)); (a) += (b); } GG(a, b, c, d, x, s, ac) { (a) += G ((b), (c), (d)) + (x) + ac; (a) = ROTATE_LEFT ((a), (s)); (a) += (b); } HH(a, b, c, d, x, s, ac) { (a) += H ((b), (c), (d)) + (x) + ac; (a) = ROTATE_LEFT ((a), (s)); (a) += (b); } II(a, b, c, d, x, s, ac) { (a) += I ((b), (c), (d)) + (x) + ac; (a) = ROTATE_LEFT ((a), (s)); (a) += (b); }