MD5使用

         MD5即Message-Digest Algorithm 5（信息-摘要算法 5），用于确保信息传输完整一致。是计算机广泛使用的散列算法之一（又译摘要算法、哈希算法），主流编程语言普遍已有MD5实现。将数据（如汉字）运算为另一固定长度值，是散列算法的基础原理，MD5的前身有MD2、MD3和MD4。

        MD5较老，散列长度通常为128位，随着计算机运算能力提高，找到“碰撞”是可能的。因此，在安全要求高的场合不使用MD5。

        2004年，王小云证明MD5数字签名算法可以产生碰撞。2007年，Marc Stevens，Arjen K. Lenstra和Benne de Weger进一步指出通过伪造软件签名，可重复性攻击MD5算法。研究者使用前缀碰撞法（chosen-prefix collision），使程序前端包含恶意程序，利用后面的空间添上垃圾代码凑出同样的MD5 Hash值。

        2007年，荷兰埃因霍芬技术大学科学家成功把2个可执行文件进行了MD5碰撞，使得这两个运行结果不同的程序被计算出同一个MD5。2008年12月一组科研人员通过MD5碰撞成功生成了伪造的SSL证书，这使得在https协议中服务器可以伪造一些根CA的签名。

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 
  
    . * 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 
  
    . * Still in the public domain. */ #include 
   
     /* for memcpy() */ #ifndef _WIN32_WCE #include 
    
      /* for stupid systems */ #else #include 
     
       #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] = 0x; ctx->buf[1] = 0xefcdab89; ctx->buf[2] = 0x98badcfe; ctx->buf[3] = 0x; 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< 
      >(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] + 0xdb, 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] + 0xa, 17); MD5STEP(F1, b, c, d, a, in[7] + 0xfd, 22); MD5STEP(F1, a, b, c, d, in[8] + 0xd8, 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] + 0x6b, 7); MD5STEP(F1, d, a, b, c, in[13] + 0xfd, 12); MD5STEP(F1, c, d, a, b, in[14] + 0xae, 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] + 0x0, 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] + 0xf, 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] + 0xa, 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; } #endif 
      
     
    
  

3、MD5使用

#include "aemd5.h" #include "../src/aemd5.cpp" CString GetPassEncrypt(const char encrypt[16]) { // 存放于加密的信息 unsigned char decrypt[17]; // 初始化用于md5加密的结构 MD5Context md5; MD5Init(&md5); // 对欲加密的字符进行加密 MD5Update(&md5, (const unsigned char *)encrypt, strlen((char *)encrypt)); // 获得最终结果 MD5Final(&md5, decrypt); CString strEncrypt = "", strTemp; for (int i = 0; i < 16; i++) { strTemp.Format("%x", decrypt[i]); strEncrypt += strTemp; } return strEncrypt; }

加密后密文：c0c5398cf945c3b3dda2c41