c语言实现MD5算法

MD5加密

MD5介绍

 1。 一种单向加密算法，即对明文加密，而不能通过密文得到明文。对原数据的任何改动，哪怕是1字节，得到的MD5值都有很大的区别。可以用公式表示：密文=Md5_calc(原文数据)；

应用场景

1.密码认证；
2.数据校验：

代码分析 （基于qt5.14.2）

md5.c

#include 
#include "md5.h"

#define F(x,y,z) ((x & y) | (~x & z))
#define G(x,y,z) ((x & z) | (y & ~z))
#define H(x,y,z) (x^y^z)
#define I(x,y,z) (y ^ (x | ~z))
#define ROTATE_LEFT(x,n) ((x << n) | (x >> (32-n)))
#define FF(a,b,c,d,x,s,ac) \
    { \
        a += F(b,c,d) + x + ac; \
        a = ROTATE_LEFT(a,s); \
        a += b; \
    }
#define GG(a,b,c,d,x,s,ac) \
    { \
        a += G(b,c,d) + x + ac; \
        a = ROTATE_LEFT(a,s); \
        a += b; \
    }
#define HH(a,b,c,d,x,s,ac) \
    { \
        a += H(b,c,d) + x + ac; \
        a = ROTATE_LEFT(a,s); \
        a += b; \
    }
#define II(a,b,c,d,x,s,ac) \
    { \
        a += I(b,c,d) + x + ac; \
        a = ROTATE_LEFT(a,s); \
        a += b; \
    }

void MD5Transform(unsigned int state[4],unsigned char block[64]);
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len);
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len);

unsigned char PADDING[] = {
    0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
};

void MD5Init(MD5_CTX *context) {
    context->count[0] = 0;
    context->count[1] = 0;
    context->state[0] = 0x67452301;
    context->state[1] = 0xEFCDAB89;
    context->state[2] = 0x98BADCFE;
    context->state[3] = 0x10325476;
}
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen)
{
    unsigned int i = 0,index = 0,partlen = 0;
    index = (context->count[0] >> 3) & 0x3F;
    partlen = 64 - index;
    context->count[0] += inputlen << 3;
    if(context->count[0] < (inputlen << 3)) {
        context->count[1]++;
    }
    context->count[1] += inputlen >> 29;

    if(inputlen >= partlen) {
        memcpy(&context->buffer[index],input,partlen);
        MD5Transform(context->state,context->buffer);
        for(i = partlen;i+64 <= inputlen;i+=64) {
            MD5Transform(context->state,&input[i]);
        }
        index = 0;
    } else {
        i = 0;
    }

    memcpy(&context->buffer[index],&input[i],inputlen-i);
}

void MD5Final(MD5_CTX *context,unsigned char digest[16]) {
    unsigned int index = 0,padlen = 0;
    unsigned char bits[8];
    index = (context->count[0] >> 3) & 0x3F;
    padlen = (index < 56)?(56-index):(120-index);
    MD5Encode(bits,context->count,8);
    MD5Update(context,PADDING,padlen);
    MD5Update(context,bits,8);
    MD5Encode(digest,context->state,16);
}
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len) {
    unsigned int i = 0,j = 0;
    while(j < len) {
        output[j] = input[i] & 0xFF;
        output[j+1] = (input[i] >> 8) & 0xFF;
        output[j+2] = (input[i] >> 16) & 0xFF;
        output[j+3] = (input[i] >> 24) & 0xFF;
        i++;
        j+=4;
    }
}
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len) {
    unsigned int i = 0,j = 0;
    while(j < len) {
        output[i] = (input[j]) | (input[j+1] << 8) | (input[j+2] << 16) | (input[j+3] << 24);
        i++;
        j+=4;
    }
}
void MD5Transform(unsigned int state[4],unsigned char block[64]) {
    unsigned int a = state[0];
    unsigned int b = state[1];
    unsigned int c = state[2];
    unsigned int d = state[3];
    unsigned int x[64];

    MD5Decode(x,block,64);

    FF(a, b, c, d, x[ 0], 7, 0xd76aa478);
    FF(d, a, b, c, x[ 1], 12, 0xe8c7b756);
    FF(c, d, a, b, x[ 2], 17, 0x242070db);
    FF(b, c, d, a, x[ 3], 22, 0xc1bdceee);
    FF(a, b, c, d, x[ 4], 7, 0xf57c0faf);
    FF(d, a, b, c, x[ 5], 12, 0x4787c62a);
    FF(c, d, a, b, x[ 6], 17, 0xa8304613);
    FF(b, c, d, a, x[ 7], 22, 0xfd469501);
    FF(a, b, c, d, x[ 8], 7, 0x698098d8);
    FF(d, a, b, c, x[ 9], 12, 0x8b44f7af);
    FF(c, d, a, b, x[10], 17, 0xffff5bb1);
    FF(b, c, d, a, x[11], 22, 0x895cd7be);
    FF(a, b, c, d, x[12], 7, 0x6b901122);
    FF(d, a, b, c, x[13], 12, 0xfd987193);
    FF(c, d, a, b, x[14], 17, 0xa679438e);
    FF(b, c, d, a, x[15], 22, 0x49b40821);

    GG(a, b, c, d, x[ 1], 5, 0xf61e2562);
    GG(d, a, b, c, x[ 6], 9, 0xc040b340);
    GG(c, d, a, b, x[11], 14, 0x265e5a51);
    GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);
    GG(a, b, c, d, x[ 5], 5, 0xd62f105d);
    GG(d, a, b, c, x[10], 9,  0x2441453);
    GG(c, d, a, b, x[15], 14, 0xd8a1e681);
    GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);
    GG(a, b, c, d, x[ 9], 5, 0x21e1cde6);
    GG(d, a, b, c, x[14], 9, 0xc33707d6);
    GG(c, d, a, b, x[ 3], 14, 0xf4d50d87);
    GG(b, c, d, a, x[ 8], 20, 0x455a14ed);
    GG(a, b, c, d, x[13], 5, 0xa9e3e905);
    GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8);
    GG(c, d, a, b, x[ 7], 14, 0x676f02d9);
    GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);


    HH(a, b, c, d, x[ 5], 4, 0xfffa3942);
    HH(d, a, b, c, x[ 8], 11, 0x8771f681);
    HH(c, d, a, b, x[11], 16, 0x6d9d6122);
    HH(b, c, d, a, x[14], 23, 0xfde5380c);
    HH(a, b, c, d, x[ 1], 4, 0xa4beea44);
    HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);
    HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60);
    HH(b, c, d, a, x[10], 23, 0xbebfbc70);
    HH(a, b, c, d, x[13], 4, 0x289b7ec6);
    HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);
    HH(c, d, a, b, x[ 3], 16, 0xd4ef3085);
    HH(b, c, d, a, x[ 6], 23,  0x4881d05);
    HH(a, b, c, d, x[ 9], 4, 0xd9d4d039);
    HH(d, a, b, c, x[12], 11, 0xe6db99e5);
    HH(c, d, a, b, x[15], 16, 0x1fa27cf8);
    HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);


    II(a, b, c, d, x[ 0], 6, 0xf4292244);
    II(d, a, b, c, x[ 7], 10, 0x432aff97);
    II(c, d, a, b, x[14], 15, 0xab9423a7);
    II(b, c, d, a, x[ 5], 21, 0xfc93a039);
    II(a, b, c, d, x[12], 6, 0x655b59c3);
    II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);
    II(c, d, a, b, x[10], 15, 0xffeff47d);
    II(b, c, d, a, x[ 1], 21, 0x85845dd1);
    II(a, b, c, d, x[ 8], 6, 0x6fa87e4f);
    II(d, a, b, c, x[15], 10, 0xfe2ce6e0);
    II(c, d, a, b, x[ 6], 15, 0xa3014314);
    II(b, c, d, a, x[13], 21, 0x4e0811a1);
    II(a, b, c, d, x[ 4], 6, 0xf7537e82);
    II(d, a, b, c, x[11], 10, 0xbd3af235);
    II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb);
    II(b, c, d, a, x[ 9], 21, 0xeb86d391);
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
}

md5.h

#ifndef MD5_H
#define MD5_H

typedef struct
{
    unsigned int count[2];
    unsigned int state[4];
    unsigned char buffer[64];
}MD5_CTX;

void MD5Init(MD5_CTX *context);
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen);
void MD5Final(MD5_CTX *context,unsigned char digest[16]);

#endif

main.c

#include 

extern "C"{         //添加头文件
    #include "md5.h"
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    int i, n;
    bool isfile = false;
    unsigned char decrypt[16];
    MD5_CTX md5;

    if(argc > 1 && strlen(argv[1]) == 2 && !memcmp(argv[1], "-f", 2)) {
        isfile = true;
    }

    if(argc == 1 || (argc == 2 && isfile)) {
        fprintf(stderr, "usage:\n    %s -f file ...\n    %s string ...\n", argv[0], argv[0]);
        return 1;
    }

    if(isfile) {
        FILE *fp;
        for(n=2; n<argc; n++) {
            fp = fopen(argv[n], "rb");
            if(fp == NULL) {
                fprintf(stderr, "File %s not exists, errno = %d, error = %s\n", argv[n], errno, strerror(errno));
                continue;
            }

            MD5Init(&md5);

            do {
                unsigned char encrypt[1024];
                while(!feof(fp)) {
                    MD5Update(&md5, encrypt, fread(encrypt, 1, sizeof(encrypt), fp));
                }
                fclose(fp);
            } while(0);

            MD5Final(&md5, decrypt);

            for(i=0; i<16; i++) {
                printf("%02x", decrypt[i]);  //02x前需要加上 %
            }

            printf("  %s\n", argv[n]);
        }
    } else {
        for(n=1; n<argc; n++) {
            MD5Init(&md5);
            MD5Update(&md5,(unsigned char*) argv[n], strlen(argv[n]));
            MD5Final(&md5, decrypt);

            for(i=0; i<16; i++) {
                printf("%02x", decrypt[i]);  //02x前需要加上 %
            }

            printf("  %s\n", argv[n]);
        }
    }
    return a.exec();
}

测试记录

1. 源码打包（windeployqt.exe工具），得到MD5.exe
   
2. 运行测试，创建一个test.txt文件，打开文件写入：123，保存关闭，运行如下测试命令：MD5.exe -f test.txt 得到密文：202cb962ac59075b964b07152d234b70
   
3. 测试准确性，利用在线工具，输入：123得到相同的密文，验证成功。