MD5即Message-Digest Algorithm 5（信息-摘要算法 5），用於確保信息傳輸完整一致。是計算機廣泛使用的散列算法之一（又譯摘要算法、哈希算法），主流編程語言普遍已有MD5實現。將數據（如漢字）運算爲另一固定長度值，是散列算法的基礎原理，MD5的前身有MD2、MD3和MD4。
MD5較老，散列長度通常爲128位，隨着計算機運算能力提高，找到“碰撞”是可能的。因此，在安全要求高的場合不使用MD5。
2004年，王小云證明MD5數字簽名算法可以產生碰撞。2007年，Marc Stevens，Arjen K. Lenstra和Benne de Weger進一步指出通過僞造軟件簽名，可重複性攻擊MD5算法。研究者使用前綴碰撞法（chosen-prefix collision），使程序前端包含惡意程序，利用後面的空間添上垃圾代碼湊出同樣的MD5 Hash值。
2007年，荷蘭埃因霍芬技術大學科學家成功把2個可執行文件進行了MD5碰撞，使得這兩個運行結果不同的程序被計算出同一個MD5。2008年12月一組科研人員通過MD5碰撞成功生成了僞造的SSL證書，這使得在https協議中服務器可以僞造一些根CA的簽名。
1、AEMD5.h
/*
* This is the header file for the MD5 message-digest algorithm.
* The algorithm is due to Ron Rivest. This code was
* written by Colin Plumb in 1993, no copyright is claimed.
* This code is in the public domain; do with it what you wish.
*
* Equivalent code is available from RSA Data Security, Inc.
* This code has been tested against that, and is equivalent,
* except that you don't need to include two pages of legalese
* with every copy.
*
* To compute the message digest of a chunk of bytes, declare an
* MD5Context structure, pass it to MD5Init, call MD5Update as
* needed on buffers full of bytes, and then call MD5Final, which
* will fill a supplied 16-byte array with the digest.
*
* Changed so as no longer to depend on Colin Plumb's `usual.h'
* header definitions; now uses stuff from dpkg's config.h
* - Ian Jackson <[email protected]>.
* Still in the public domain.
*/
#ifndef _AEMD5_H_
#define _AEMD5_H_
typedef unsigned char md5byte;
typedef unsigned int UWORD32;
struct MD5Context
{
UWORD32 buf[4];
UWORD32 bytes[2];
UWORD32 in[16];
};
static void MD5Init(struct MD5Context *context);
static void MD5Update(struct MD5Context *context, md5byte const *buf, unsigned len);
static void MD5Final(struct MD5Context *context, unsigned char digest[16]);
static void MD5Transform(UWORD32 buf[4], UWORD32 const in[16]);
#endif // _AEMD5_H_2、AEMD5.cpp
/*
* This code implements the MD5 message-digest algorithm.
* The algorithm is due to Ron Rivest. This code was
* written by Colin Plumb in 1993, no copyright is claimed.
* This code is in the public domain; do with it what you wish.
*
* Equivalent code is available from RSA Data Security, Inc.
* This code has been tested against that, and is equivalent,
* except that you don't need to include two pages of legalese
* with every copy.
*
* To compute the message digest of a chunk of bytes, declare an
* MD5Context structure, pass it to MD5Init, call MD5Update as
* needed on buffers full of bytes, and then call MD5Final, which
* will fill a supplied 16-byte array with the digest.
*
* Changed so as no longer to depend on Colin Plumb's `usual.h' header
* definitions; now uses stuff from dpkg's config.h.
* - Ian Jackson <[email protected]>.
* Still in the public domain.
*/
#include <string.h> /* for memcpy() */
#ifndef _WIN32_WCE
#include <sys/types.h> /* for stupid systems */
#else
#include <types.h>
#endif
#include "aemd5.h"
static void
byteSwap(UWORD32 *buf, unsigned words)
{
const unsigned int byteOrderTest = 0x1;
if (((char *)&byteOrderTest)[0] == 0) {
md5byte *p = (md5byte *)buf;
do {
*buf++ = (UWORD32)((unsigned)p[3] << 8 | p[2]) << 16 |
((unsigned)p[1] << 8 | p[0]);
p += 4;
} while (--words);
}
}
/*
* Start MD5 accumulation. Set bit count to 0 and buffer to mysterious
* initialization constants.
*/
static void
MD5Init(struct MD5Context *ctx)
{
ctx->buf[0] = 0x67452301;
ctx->buf[1] = 0xefcdab89;
ctx->buf[2] = 0x98badcfe;
ctx->buf[3] = 0x10325476;
ctx->bytes[0] = 0;
ctx->bytes[1] = 0;
}
/*
* Update context to reflect the concatenation of another buffer full
* of bytes.
*/
static void
MD5Update(struct MD5Context *ctx, md5byte const *buf, unsigned len)
{
UWORD32 t;
/* Update byte count */
t = ctx->bytes[0];
if ((ctx->bytes[0] = t + len) < t)
ctx->bytes[1]++; /* Carry from low to high */
t = 64 - (t & 0x3f); /* Space available in ctx->in (at least 1) */
if (t > len) {
memcpy((md5byte *)ctx->in + 64 - t, buf, len);
return;
}
/* First chunk is an odd size */
memcpy((md5byte *)ctx->in + 64 - t, buf, t);
byteSwap(ctx->in, 16);
MD5Transform(ctx->buf, ctx->in);
buf += t;
len -= t;
/* Process data in 64-byte chunks */
while (len >= 64) {
memcpy(ctx->in, buf, 64);
byteSwap(ctx->in, 16);
MD5Transform(ctx->buf, ctx->in);
buf += 64;
len -= 64;
}
/* Handle any remaining bytes of data. */
memcpy(ctx->in, buf, len);
}
/*
* Final wrapup - pad to 64-byte boundary with the bit pattern
* 1 0* (64-bit count of bits processed, MSB-first)
*/
static void
MD5Final(struct MD5Context *ctx, md5byte digest[16])
{
int count = ctx->bytes[0] & 0x3f; /* Number of bytes in ctx->in */
md5byte *p = (md5byte *)ctx->in + count;
/* Set the first char of padding to 0x80. There is always room. */
*p++ = 0x80;
/* Bytes of padding needed to make 56 bytes (-8..55) */
count = 56 - 1 - count;
if (count < 0) { /* Padding forces an extra block */
memset(p, 0, count + 8);
byteSwap(ctx->in, 16);
MD5Transform(ctx->buf, ctx->in);
p = (md5byte *)ctx->in;
count = 56;
}
memset(p, 0, count);
byteSwap(ctx->in, 14);
/* Append length in bits and transform */
ctx->in[14] = ctx->bytes[0] << 3;
ctx->in[15] = ctx->bytes[1] << 3 | ctx->bytes[0] >> 29;
MD5Transform(ctx->buf, ctx->in);
byteSwap(ctx->buf, 4);
memcpy(digest, ctx->buf, 16);
memset(ctx, 0, sizeof(ctx)); /* In case it's sensitive */
}
#ifndef ASM_MD5
/* The four core functions - F1 is optimized somewhat */
/* #define F1(x, y, z) (x & y | ~x & z) */
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))
/* This is the central step in the MD5 algorithm. */
#define MD5STEP(f,w,x,y,z,in,s) \
(w += f(x,y,z) + in, w = (w<<s | w>>(32-s)) + x)
/*
* The core of the MD5 algorithm, this alters an existing MD5 hash to
* reflect the addition of 16 longwords of new data. MD5Update blocks
* the data and converts bytes into longwords for this routine.
*/
static void
MD5Transform(UWORD32 buf[4], UWORD32 const in[16])
{
register UWORD32 a, b, c, d;
a = buf[0];
b = buf[1];
c = buf[2];
d = buf[3];
MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);
MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);
MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);
MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);
buf[0] += a;
buf[1] += b;
buf[2] += c;
buf[3] += d;
}
#endif3、MD5使用
#include "aemd5.h"
#include "../src/aemd5.cpp"
CString GetPassEncrypt(const char encrypt[16])
{
// 存放於加密的信息
unsigned char decrypt[17];
// 初始化用於md5加密的結構
MD5Context md5;
MD5Init(&md5);
// 對欲加密的字符進行加密
MD5Update(&md5, (const unsigned char *)encrypt, strlen((char *)encrypt));
// 獲得最終結果
MD5Final(&md5, decrypt);
CString strEncrypt = "", strTemp;
for (int i = 0; i < 16; i++)
{
strTemp.Format("%x", decrypt[i]);
strEncrypt += strTemp;
}
return strEncrypt;
}
加密前明文：liuxuezong
加密後密文：c0c5398c97682793f945c3b3dda2c41
