MD5算法

awenst

于 2017-03-14 18:17:28 发布

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分类专栏：信息安全

本文链接：https://blog.youkuaiyun.com/awenst/article/details/62047705

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本文介绍了一种使用C语言实现的MD5加密算法。通过详细展示MD5算法的具体步骤，包括初始化、消息预处理、迭代处理及输出结果等，帮助读者理解MD5的工作原理。

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实现信息安全中基本的加密算法MD5.

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
FILE *input;
FILE *output;
unsigned int r[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 };
unsigned int k[64];
unsigned int h0 = 0x67452301;
unsigned int h1 = 0xEFCDAB89;
unsigned int h2 = 0x98BADCFE;
unsigned int h3 = 0x10325476;
char mess[];
int main(int argc, char* argv[]){
	int i;
	fopen_s(&input,"C:\\Users\Administrator\Desktop\12330296_汪欣言_Assign_1\message.txt", "r");
	i = ftell(input);
	if (i == -1L) {
		printf("error~!");
		exit(0);
	}
	fseek(input, 0, SEEK_END);
	int size = ftell(input);
	fseek(input, 0, SEEK_SET);
	fread(mess, size, 1, input);
	for (i = 0; i < 64; i++) {
		k[i] = (unsigned int)(floor((fabs(sin((float)(i + 1)))) * pow((float)2,(float) 32)));
	}
	//
	unsigned long long messLength = (unsigned long long)strlen(mess) * 8;
	mess[strlen(mess) + 1] = '\0';
	mess[strlen(mess)] = 1 << 7;


	int x = strlen(mess) % 64;
	if (x <= 56) {
		x = 56 - x;
	}
	else {
		x = 64 - (x - 56);
	}
	for (i = 0; i < x; i++) {
		mess[strlen(mess) + i] = 0;
	}
	int length = strlen(mess) + x;
	//printf("%d\n", length);
	//printf("%d\n", sizeof(unsigned long long));
	mess[length + 7] = (char)(messLength >> 56);
	mess[length + 6] = (char)(messLength >> 48);
	mess[length + 5] = (char)(messLength >> 40);
	mess[length + 4] = (char)(messLength >> 32);
	mess[length + 3] = (char)(messLength >> 24);
	mess[length + 2] = (char)(messLength >> 16);
	mess[length + 1] = (char)(messLength >> 8);
	mess[length] = (char)(messLength);
	length = length + 8;
	mess[length] = 0;
	unsigned long long Length = (unsigned long long)length * 8;
	//printf("%ld\n", messLength);
	//unsigned 
	//printf("%ld\n", Length);
	unsigned int j;
	unsigned int temp;
	unsigned int w[16];
	unsigned int a, b, c, d, f, g;
	//char bb;
	//bb = 1;
	//printf("%d\n", (int)bb << 32);

	for (i = 0; i < Length / 512; i++){
		for (j = 0; j < 16; j++){
			temp = i * 64 + j * 4;
			w[j] = ((int)mess[temp]) | ((int)mess[temp + 1] << 8) | ((int)mess[temp + 2] << 16) | ((int)mess[temp + 3] << 24);
		}
		a = h0;
		b = h1;
		c = h2;
		d = h3;

		for (j = 0; j < 64; j++) {
			if (0 <= j && j <= 15) {
				f = (b & c) | ((~b) & d);
				g = j;
			}
			else if (16 <= j && j <= 31) {
				f = (d & b) | ((~d) & c);
				g = (5 * j + 1) % 16;
			}
			else if (32 <= j && j <= 47) {
				f = b ^ c ^ d;
				g = (3 * j + 5) % 16;
			}
			else if (48 <= j && j <= 63) {
				f = c ^ (b | (~d));
				g = (7 * j) % 16;
			}
			temp = d;
			d = c;
			c = b;
			b = (((a + f + k[j] + w[g]) << r[j]) | ((a + f + k[j] + w[g]) >> (32 - r[j]))) + b;
			//b = (r[j] << (a + f + k[j] + w[g])) | (r[j] >> (32 - (a + f + k[j] + w[g]))) + b;
			a = temp;
		}
		h0 += a;
		h1 += b;
		h2 += c;
		h3 += d;
	}
	//	printf("%d %d\n", length, x);
	//	printf("%d\n", sizeof(int));
	//
	char ans[17];
	//sprintf(ans, "%u %u %u %u\n", h0, h1, h2, h3);
	h0 = ((0x000000FF & h0) << 24) | ((0x0000FF00 & h0) << 8) | ((0x00FF0000 & h0) >> 8) | ((0xFF000000 & h0) >> 24);
	h1 = ((0x000000FF & h1) << 24) | ((0x0000FF00 & h1) << 8) | ((0x00FF0000 & h1) >> 8) | ((0xFF000000 & h1) >> 24);
	h2 = ((0x000000FF & h2) << 24) | ((0x0000FF00 & h2) << 8) | ((0x00FF0000 & h2) >> 8) | ((0xFF000000 & h2) >> 24);
	h3 = ((0x000000FF & h3) << 24) | ((0x0000FF00 & h3) << 8) | ((0x00FF0000 & h3) >> 8) | ((0xFF000000 & h3) >> 24);
	printf("%02x%02x%02x%02x\n", h0, h1, h2, h3);
	fopen_s(&output,"C:\\Users\Administrator\Desktop\result.txt", "w");
	fprintf(output, "%02x%02x%02x%02x\n", h0, h1, h2, h3);
	fclose(input);
	fclose(output);
	scanf_s("%d");
	return 0;
}