代码如下:

using System;
using System.Collections.Generic;
using System.Text;

namespace MYMD5
{
 public class MD5
 {
 const int BITS_TO_A_BYTE = 8;
 const int BYTES_TO_A_WORD = 4;
 const int BITS_TO_A_WORD = 32;
 private static long[] m_lOnBits = new long[30 + 1];
 private static long[] m_l2Power = new long[30 + 1];

 private static long LShift(long lValue, long iShiftBits)
 {
 long LShift = 0;
 if (iShiftBits == 0)
 {
 LShift = lValue;
 return LShift;
 }
 else
 {
 if (iShiftBits == 31)
 {
 if (Convert.ToBoolean(lValue & 1))
 {
 LShift = 0x80000000;
 }
 else
 {
 LShift = 0;
 }
 return LShift;
 }
 else
 {
 if (iShiftBits 31)
 {
 // Err.Raise 6;
 }
 }
 }

 if (Convert.ToBoolean((lValue & m_l2Power[31 – iShiftBits])))
 {
 LShift = ((lValue & m_lOnBits[31 – (iShiftBits + 1)]) * m_l2Power[iShiftBits]) | 0x80000000;
 }
 else
 {
 LShift = ((lValue & m_lOnBits[31 – iShiftBits]) * m_l2Power[iShiftBits]);
 }

 return LShift;
 }

 private static long RShift(long lValue, long iShiftBits)
 {
 long RShift = 0;
 if (iShiftBits == 0)
 {
 RShift = lValue;
 return RShift;
 }
 else
 {
 if (iShiftBits == 31)
 {
 if (Convert.ToBoolean(lValue & 0x80000000))
 {
 RShift = 1;
 }
 else
 {
 RShift = 0;
 }
 return RShift;
 }
 else
 {
 if (iShiftBits 31)
 {
 // Err.Raise 6;
 }
 }
 }

 RShift = (lValue & 0x7FFFFFFE) / m_l2Power[iShiftBits];

 if (Convert.ToBoolean((lValue & 0x80000000)))
 {
 RShift = (RShift | (0x40000000 / m_l2Power[iShiftBits – 1]));
 }

 return RShift;
 }

 private static long RotateLeft(long lValue, long iShiftBits)
 {
 long RotateLeft = 0;
 RotateLeft = LShift(lValue, iShiftBits) | RShift(lValue, (32 – iShiftBits));
 return RotateLeft;
 }

 private static long AddUnsigned(long lX, long lY)
 {
 long AddUnsigned = 0;
 long lX4 = 0;
 long lY4 = 0;
 long lX8 = 0;
 long lY8 = 0;
 long lResult = 0;

 lX8 = lX & 0x80000000;
 lY8 = lY & 0x80000000;
 lX4 = lX & 0x40000000;
 lY4 = lY & 0x40000000;

 lResult = (lX & 0x3FFFFFFF) + (lY & 0x3FFFFFFF);
 if (Convert.ToBoolean(lX4 & lY4))
 {
 lResult = lResult ^ 0x80000000 ^ lX8 ^ lY8;
 }
 else if (Convert.ToBoolean(lX4 | lY4))
 {
 if (Convert.ToBoolean(lResult & 0x40000000))
 {
 lResult = lResult ^ 0xC0000000 ^ lX8 ^ lY8;
 }
 else
 {
 lResult = lResult ^ 0x40000000 ^ lX8 ^ lY8;
 }
 }
 else
 {
 lResult = lResult ^ lX8 ^ lY8;
 }
 AddUnsigned = lResult;
 return AddUnsigned;
 }

 private static long md5_F(long x, long y, long z)
 {
 long md5_F = 0;
 md5_F = (x & y) | ((~x) & z);
 return md5_F;
 }

 private static long md5_G(long x, long y, long z)
 {
 long md5_G = 0;
 md5_G = (x & z) | (y & (~z));
 return md5_G;
 }

 private static long md5_H(long x, long y, long z)
 {
 long md5_H = 0;
 md5_H = (x ^ y ^ z);
 return md5_H;
 }

 private static long md5_I(long x, long y, long z)
 {
 long md5_I = 0;
 md5_I = (y ^ (x | (~z)));
 return md5_I;
 }

 private static void md5_FF(ref long a, long b, long c, long d, long x, long s, long ac)
 {
 a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_F(b, c, d), x), ac));
 a = RotateLeft(a, s);
 a = AddUnsigned(a, b);
 }

 private static void md5_GG(ref long a, long b, long c, long d, long x, long s, long ac)
 {
 a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_G(b, c, d), x), ac));
 a = RotateLeft(a, s);
 a = AddUnsigned(a, b);
 }

 private static void md5_HH(ref long a, long b, long c, long d, long x, long s, long ac)
 {
 a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_H(b, c, d), x), ac));
 a = RotateLeft(a, s);
 a = AddUnsigned(a, b);
 }

 private static void md5_II(ref long a, long b, long c, long d, long x, long s, long ac)
 {
 a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_I(b, c, d), x), ac));
 a = RotateLeft(a, s);
 a = AddUnsigned(a, b);
 }

 private static long[] ConvertToWordArray(string sMessage)
 {
 long[] ConvertToWordArray = null;
 int lMessageLength = 0;
 int lNumberOfWords = 0;
 long[] lWordArray = null;
 int lBytePosition = 0;
 int lByteCount = 0;
 int lWordCount = 0;

 const int MODULUS_BITS = 512;
 const int CONGRUENT_BITS = 448;

 lMessageLength = sMessage.Length;
 lNumberOfWords = (((lMessageLength + ((MODULUS_BITS – CONGRUENT_BITS) / BITS_TO_A_BYTE)) / (MODULUS_BITS / BITS_TO_A_BYTE)) + 1) * (MODULUS_BITS / BITS_TO_A_WORD);
 lWordArray = new long[lNumberOfWords];

 lBytePosition = 0;
 lByteCount = 0;

 while (lByteCount {
 lWordCount = lByteCount / BYTES_TO_A_WORD;
 lBytePosition = (lByteCount % BYTES_TO_A
 _WORD) * BITS_TO_A_BYTE;
 lWordArray[lWordCount] = lWordArray[lWordCount] | LShift(Convert.ToByte(sMessage.Substring(lByteCount, 1).ToCharArray()[0]), lBytePosition);
 lByteCount = lByteCount + 1;
 }

 lWordCount = lByteCount / BYTES_TO_A_WORD;
 lBytePosition = (lByteCount % BYTES_TO_A_WORD) * BITS_TO_A_BYTE;
 lWordArray[lWordCount] = lWordArray[lWordCount] | LShift(0x80, lBytePosition);
 lWordArray[lNumberOfWords – 2] = LShift(lMessageLength, 3);
 lWordArray[lNumberOfWords – 1] = RShift(lMessageLength, 29);
 ConvertToWordArray = lWordArray;

 return ConvertToWordArray;
 }

 private static string WordToHex(long lValue)
 {
 string WordToHex = “”;
 long lByte = 0;
 int lCount = 0;
 for (lCount = 0; lCount {
 lByte = RShift(lValue, lCount * BITS_TO_A_BYTE) & m_lOnBits[BITS_TO_A_BYTE – 1];
 WordToHex = WordToHex + ((“0” + ToHex(lByte)).Substring((“0” + ToHex(lByte)).Length – 2));
 }
 return WordToHex;
 }

 private static string ToHex(long dec)
 {
 string strhex = “”;
 while (dec > 0)
 {
 strhex = tohex(dec % 16) + strhex;
 dec = dec / 16;
 }
 return strhex;
 }

 private static string tohex(long hex)
 {
 string strhex = “”;
 switch (hex)
 {
 case 10: strhex = “a”; break;
 case 11: strhex = “b”; break;
 case 12: strhex = “c”; break;
 case 13: strhex = “d”; break;
 case 14: strhex = “e”; break;
 case 15: strhex = “f”; break;
 default: strhex = hex.ToString(); break;
 }
 return strhex;
 }

 public static string Encrypt(string sMessage, int stype)
 {
 string MD5 = “”;

 for (int i = 0; i {
 m_lOnBits[i] = Convert.ToInt64(Math.Pow(2, i + 1) – 1);
 m_l2Power[i] = Convert.ToInt64(Math.Pow(2, i));
 }

 long[] x = null;
 int k = 0;
 long AA = 0;
 long BB = 0;
 long CC = 0;
 long DD = 0;
 long a = 0;
 long b = 0;
 long c = 0;
 long d = 0;

 const int S11 = 7;
 const int S12 = 12;
 const int S13 = 17;
 const int S14 = 22;
 const int S21 = 5;
 const int S22 = 9;
 const int S23 = 14;
 const int S24 = 20;
 const int S31 = 4;
 const int S32 = 11;
 const int S33 = 16;
 const int S34 = 23;
 const int S41 = 6;
 const int S42 = 10;
 const int S43 = 15;
 const int S44 = 21;

 x = ConvertToWordArray(sMessage);

 a = 0x67452301;
 b = 0xEFCDAB89;
 c = 0x98BADCFE;
 d = 0x10325476;

 for (k = 0; k {
 AA = a;
 BB = b;
 CC = c;
 DD = d;

 md5_FF(ref a, b, c, d, x[k + 0], S11, 0xD76AA478);
 md5_FF(ref d, a, b, c, x[k + 1], S12, 0xE8C7B756);
 md5_FF(ref c, d, a, b, x[k + 2], S13, 0x242070DB);
 md5_FF(ref b, c, d, a, x[k + 3], S14, 0xC1BDCEEE);
 md5_FF(ref a, b, c, d, x[k + 4], S11, 0xF57C0FAF);
 md5_FF(ref d, a, b, c, x[k + 5], S12, 0x4787C62A);
 md5_FF(ref c, d, a, b, x[k + 6], S13, 0xA8304613);
 md5_FF(ref b, c, d, a, x[k + 7], S14, 0xFD469501);
 md5_FF(ref a, b, c, d, x[k + 8], S11, 0x698098D8);
 md5_FF(ref d, a, b, c, x[k + 9], S12, 0x8B44F7AF);
 md5_FF(ref c, d, a, b, x[k + 10], S13, 0xFFFF5BB1);
 md5_FF(ref b, c, d, a, x[k + 11], S14, 0x895CD7BE);
 md5_FF(ref a, b, c, d, x[k + 12], S11, 0x6B901122);
 md5_FF(ref d, a, b, c, x[k + 13], S12, 0xFD987193);
 md5_FF(ref c, d, a, b, x[k + 14], S13, 0xA679438E);
 md5_FF(ref b, c, d, a, x[k + 15], S14, 0x49B40821);
 md5_GG(ref a, b, c, d, x[k + 1], S21, 0xF61E2562);
 md5_GG(ref d, a, b, c, x[k + 6], S22, 0xC040B340);
 md5_GG(ref c, d, a, b, x[k + 11], S23, 0x265E5A51);
 md5_GG(ref b, c, d, a, x[k + 0], S24, 0xE9B6C7AA);
 md5_GG(ref a, b, c, d, x[k + 5], S21, 0xD62F105D);
 md5_GG(ref d, a, b, c, x[k + 10], S22, 0x2441453);
 md5_GG(ref c, d, a, b, x[k + 15], S23, 0xD8A1E681);
 md5_GG(ref b, c, d, a, x[k + 4], S24, 0xE7D3FBC8);
 md5_GG(ref a, b, c, d, x[k + 9], S21, 0x21E1CDE6);
 md5_GG(ref d, a, b, c, x[k + 14], S22, 0xC33707D6);
 md5_GG(ref c, d, a, b, x[k + 3], S23, 0xF4D50D87);
 md5_GG(ref b, c, d, a, x[k + 8], S24, 0x455A14ED);
 md5_GG(ref a, b, c, d, x[k + 13], S21, 0xA9E3E905);
 md5_GG(ref d, a, b, c, x[k + 2], S22, 0xFCEFA3F8);
 md5_GG(ref c, d, a, b, x[k + 7], S23, 0x676F02D9);
 md5_GG(ref b, c, d, a, x[k + 12], S24, 0x8D2A4C8A);
 md5_HH(ref a, b, c, d, x[k + 5], S31, 0xFFFA3942);
 md5_HH(ref d, a, b, c, x[k + 8], S32, 0x8771F681);
 md5_HH(ref c, d, a, b, x[k + 11], S33, 0x6D9D6122);
 md5_HH(ref b, c, d, a, x[k + 14], S34, 0xFDE5380C);
 md5_HH(ref a, b, c, d, x[k + 1], S31, 0xA4BEEA44);
 md5_HH(ref d, a, b, c, x[k + 4], S32, 0x4BDECFA9);
 md5_HH(ref c, d, a, b, x[k + 7], S33, 0xF6BB4B60);
 md5_HH(ref b, c, d, a, x[k + 10], S34, 0xBEBFBC70);
 md5_HH(ref a, b, c, d, x[k + 13], S31, 0x289B7EC6);
 md5_HH(ref d, a, b, c, x[k + 0], S32, 0xEAA127FA);
 md5_HH(ref c, d, a, b, x[k + 3], S33, 0xD4EF3085);
 md5_HH(ref b, c, d, a, x[k + 6], S34, 0x4881D05);
 md5_HH(ref a, b, c, d, x[k + 9], S31, 0xD9D4D039);
 md5_HH(ref d, a, b, c, x[k + 12], S32, 0xE6DB99E5);
 md5_HH(ref c, d, a, b, x[k + 15], S33, 0x1FA27CF8);
 md5_HH(ref b, c, d, a, x[k + 2], S34, 0xC4AC5665);
 md5_II(ref a, b, c, d, x[k + 0], S41, 0xF4292244);
 md5_II(ref d, a, b, c, x[k + 7], S42, 0x432AFF97);
 md5_II(ref c, d, a, b, x[k + 14], S43, 0xAB9423A7);
 md5_II(ref b, c, d, a, x[k + 5], S44, 0xFC93A039);
 md5_II(ref a, b, c, d, x[k + 12], S41, 0x655B59C3);
 md5_II(ref d, a, b, c, x[k + 3], S42, 0x8F0CCC92);
 md5_II(ref c, d, a, b, x[k + 10], S43, 0xFFEFF47D);
md5_II(refb, c, d, a, x[k + 1], S44, 0x85845DD1);
 md5_II(ref a, b, c, d, x[k + 8], S41, 0x6FA87E4F);
 md5_II(ref d, a, b, c, x[k
 + 15], S42, 0xFE2CE6E0);
 md5_II(ref c, d, a, b, x[k + 6], S43, 0xA3014314);
 md5_II(ref b, c, d, a, x[k + 13], S44, 0x4E0811A1);
 md5_II(ref a, b, c, d, x[k + 4], S41, 0xF7537E82);
 md5_II(ref d, a, b, c, x[k + 11], S42, 0xBD3AF235);
 md5_II(ref c, d, a, b, x[k + 2], S43, 0x2AD7D2BB);
 md5_II(ref b, c, d, a, x[k + 9], S44, 0xEB86D391);

 a = AddUnsigned(a, AA);
 b = AddUnsigned(b, BB);
 c = AddUnsigned(c, CC);
 d = AddUnsigned(d, DD);
 }

 if (stype == 32)
 {
 MD5 = ((((WordToHex(a)) + (WordToHex(b))) + (WordToHex(c))) + (WordToHex(d))).ToLower();
 }
 else
 {
 MD5 = ((WordToHex(b)) + (WordToHex(c))).ToLower();
 }
 return MD5;
 }
 }
}

调用时,使用MD5.Encrypt(需要加密的string,加密类型16或者32)