c++编程实现基于非对称Feistel结构实验基础,写MD5压缩函数的其中一步实现
时间: 2024-03-12 16:45:52 浏览: 88
以下是C++代码实现MD5压缩函数中的消息扩展(Message Expansion)步骤:
```c++
#include <iostream>
#include <cstdint>
#include <cstring>
// 左移位数
const uint32_t s[64] = {
7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21
};
// 常数
const uint32_t K[64] = {
0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
};
// 消息扩展函数
void msg_expand(const uint8_t* msg, uint32_t* w) {
for (int i = 0; i < 16; ++i) {
w[i] = (msg[i * 4 + 3] << 24) | (msg[i * 4 + 2] << 16) | (msg[i * 4 + 1] << 8) | msg[i * 4];
}
for (int i = 16; i < 64; ++i) {
w[i] = w[i - 16] + (w[i - 16] << s[0]) + w[i - 7] + (w[i - 7] << s[1]);
}
}
int main() {
// 待处理的消息
const char* msg = "hello, world!";
// 计算消息的长度(单位:比特)
uint64_t len = strlen(msg) * 8;
// 将消息按照512位进行分组
uint8_t* msg_blocks = new uint8_t[(len + 72) / 512 * 64];
memcpy(msg_blocks, msg, strlen(msg));
msg_blocks[strlen(msg)] = 0x80;
uint64_t bit_len = len + 8;
memcpy(msg_blocks + (bit_len / 512 + 1) * 512 / 8 - 8, &len, 8);
// 对每个分组进行消息扩展
uint32_t w[64];
for (int i = 0; i < bit_len / 512 + 1; ++i) {
uint8_t* msg_block = msg_blocks + i * 64;
msg_expand(msg_block, w);
// TODO: 在压缩函数中使用w进行消息摘要计算
}
delete[] msg_blocks;
return 0;
}
```
注意:此处的代码只展示了消息扩展的实现,如果要实现完整的MD5压缩函数,还需要实现位操作函数、压缩函数等。