public classMD5_Encoding

{//RFC1321中定义的标准4*4矩阵的常量定义。

static final int S11 = 7, S12 = 12, S13 = 17, S14 = 22;static final int S21 = 5, S22 = 9, S23 = 14, S24 = 20;static final int S31 = 4, S32 = 11, S33 = 16, S34 = 23;static final int S41 = 6, S42 = 10, S43 = 15, S44 = 21;//按RFC1321标准定义不可变byte型数组PADDING

static final byte[] PADDING ={-128, 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};//MD5计算过程中的3组核心数据，采用数组形式存放

private long[] state = new long[4]; //计算状态(分别对应a b c d)

private byte[] buffer = new byte[64]; //分配64个字节私有缓冲区

private long[] count = new long[2]; //位个数//最新一次计算结果的16进制ASCII字符串表示，代表了16个字符串形式的MD5值

publicString resultStr;//最新一次计算结果的2进制数组表示，一共16个字节，代表了128bit形式的MD5值

public byte[] digest = new byte[16];//MD5_Encoding类提供的主要的接口函数getMD5ofStr，用来进行数据加密变换。调用其可对任意字符串进行加密运算，并以字符串形式返回加密结果。

publicString getMD5ofStr(String in)

{

md5Init();//初始化

md5Update(in.getBytes(), in.length());//调用MD5的主计算过程

md5Final(); //输出结果到digest数组中

for (int i = 0; i < 16; i++)

{

resultStr+= byteToHEX(digest[i]); //将digest数组中的每个byte型数据转为16进制形式的字符串

}returnresultStr;

}//标准的构造函数，调用md5Init函数进行初始化工作

publicMD5_Encoding()

{

md5Init();

}//md5初始化函数.初始化核心变量.

private voidmd5Init()

{

state[0] = 0x67452301L; //定义state为RFC1321中定义的标准幻数

state[1] = 0xefcdab89L; //定义state为RFC1321中定义的标准幻数

state[2] = 0x98badcfeL; //定义state为RFC1321中定义的标准幻数

state[3] = 0x10325476L; //定义state为RFC1321中定义的标准幻数

count[0] = count[1] = 0L; //初始化为0

resultStr = "";//初始化resultStr字符串为空

for (int i = 0; i < 16; i++)

{

digest[i]= 0;//初始化digest数组元素为0

}

}//定义F G H I 为4个基数 ，即为4个基本的MD5函数,进行简单的位运算

private long F(long x, long y, longz)

{return (x & y) | ((~x) &z);

}private long G(long x, long y, longz)

{return (x & z) | (y & (~z));

}private long H(long x, long y, longz)

{return x ^ y ^z;

}private long I(long x, long y, longz)

{return y ^ (x | (~z));

}//FF,GG,HH和II调用F,G,H,I函数进行进一步变换

private long FF(long a, long b, long c, long d, long x, long s, longac)

{

a+= F(b, c, d) + x +ac;

a= ((int) a << s) | ((int) a >>> (32 - s)); //这里long型数据右移时使用无符号右移运算符>>>

a +=b;returna;

}private long GG(long a, long b, long c, long d, long x, long s, longac)

{

a+= G(b, c, d) + x +ac;

a= ((int) a << s) | ((int) a >>> (32 - s)); //这里long型数据右移时使用无符号右移运算符>>>

a +=b;returna;

}private long HH(long a, long b, long c, long d, long x, long s, longac)

{

a+= H(b, c, d) + x +ac;

a= ((int) a << s) | ((int) a >>> (32 - s));//这里long型数据右移时使用无符号右移运算符>>>

a +=b;returna;

}private long II(long a, long b, long c, long d, long x, long s, longac)

{

a+= I(b, c, d) + x +ac;

a= ((int) a << s) | ((int) a >>> (32 - s));//这里long型数据右移时使用无符号右移运算符>>>

a +=b;returna;

}//MD5的主计算过程，input是需要变换的二进制字节串，inputlen是长度

private void md5Update(byte[] input, intinputLen)

{inti, index, partLen;byte[] block = new byte[64]; //分配64个字节缓冲区//根据count计算index值。这里long型数据右移时使用无符号右移运算符>>>

index = (int) (count[0] >>> 3) & 0x3F;if ((count[0] += (inputLen << 3)) < (inputLen << 3))

{

count[1]++;

}

count[1] += (inputLen >>> 29); //这里int型数据右移时使用无符号右移运算符>>>

partLen = 64 - index; //计算partLen值

if (inputLen >=partLen)

{

md5Memcpy(buffer, input, index,0, partLen);

md5Transform(buffer);for (i = partLen; i + 63 < inputLen; i += 64)

{

md5Memcpy(block, input,0, i, 64);

md5Transform(block);

}

index= 0;

}else{

i= 0;

}

md5Memcpy(buffer, input, index, i, inputLen-i);

}//整理和填写输出结果，结果放到数组digest中。

private voidmd5Final()

{byte[] bits = new byte[8];intindex, padLen;

Encode(bits, count,8);

index= (int) (count[0] >>> 3) & 0x3f; //这里long型数据右移时使用无符号右移运算符>>>

padLen = (index < 56) ? (56 - index) : (120 -index);

md5Update(PADDING, padLen);

md5Update(bits,8);

Encode(digest, state,16);

}//byte数组的块拷贝函数，将input数组中的起始位置为inpos，长度len的数据拷贝到output数组起始位置outpos处。

private void md5Memcpy(byte[] output, byte[] input, int outpos, intinpos,intlen)

{inti;for (i = 0; i < len; i++)

{

output[outpos+ i] = input[inpos +i];

}

}//MD5核心变换计算程序，由md5Update函数调用，block是分块的原始字节数组

private void md5Transform(byteblock[])

{long a = state[0], b = state[1], c = state[2], d = state[3];long[] x = new long[16];

Decode(x, block,64);//进行4级级联运算//第1级

a = FF(a, b, c, d, x[0], S11, 0xd76aa478L); /*1*/d= FF(d, a, b, c, x[1], S12, 0xe8c7b756L); /*2*/c= FF(c, d, a, b, x[2], S13, 0x242070dbL); /*3*/b= FF(b, c, d, a, x[3], S14, 0xc1bdceeeL); /*4*/a= FF(a, b, c, d, x[4], S11, 0xf57c0fafL); /*5*/d= FF(d, a, b, c, x[5], S12, 0x4787c62aL); /*6*/c= FF(c, d, a, b, x[6], S13, 0xa8304613L); /*7*/b= FF(b, c, d, a, x[7], S14, 0xfd469501L); /*8*/a= FF(a, b, c, d, x[8], S11, 0x698098d8L); /*9*/d= FF(d, a, b, c, x[9], S12, 0x8b44f7afL); /*10*/c= FF(c, d, a, b, x[10], S13, 0xffff5bb1L); /*11*/b= FF(b, c, d, a, x[11], S14, 0x895cd7beL); /*12*/a= FF(a, b, c, d, x[12], S11, 0x6b901122L); /*13*/d= FF(d, a, b, c, x[13], S12, 0xfd987193L); /*14*/c= FF(c, d, a, b, x[14], S13, 0xa679438eL); /*15*/b= FF(b, c, d, a, x[15], S14, 0x49b40821L); /*16*/

//第2级

a = GG(a, b, c, d, x[1], S21, 0xf61e2562L); /*17*/d= GG(d, a, b, c, x[6], S22, 0xc040b340L); /*18*/c= GG(c, d, a, b, x[11], S23, 0x265e5a51L); /*19*/b= GG(b, c, d, a, x[0], S24, 0xe9b6c7aaL); /*20*/a= GG(a, b, c, d, x[5], S21, 0xd62f105dL); /*21*/d= GG(d, a, b, c, x[10], S22, 0x2441453L); /*22*/c= GG(c, d, a, b, x[15], S23, 0xd8a1e681L); /*23*/b= GG(b, c, d, a, x[4], S24, 0xe7d3fbc8L); /*24*/a= GG(a, b, c, d, x[9], S21, 0x21e1cde6L); /*25*/d= GG(d, a, b, c, x[14], S22, 0xc33707d6L); /*26*/c= GG(c, d, a, b, x[3], S23, 0xf4d50d87L); /*27*/b= GG(b, c, d, a, x[8], S24, 0x455a14edL); /*28*/a= GG(a, b, c, d, x[13], S21, 0xa9e3e905L); /*29*/d= GG(d, a, b, c, x[2], S22, 0xfcefa3f8L); /*30*/c= GG(c, d, a, b, x[7], S23, 0x676f02d9L); /*31*/b= GG(b, c, d, a, x[12], S24, 0x8d2a4c8aL); /*32*/

//第3级

a = HH(a, b, c, d, x[5], S31, 0xfffa3942L); /*33*/d= HH(d, a, b, c, x[8], S32, 0x8771f681L); /*34*/c= HH(c, d, a, b, x[11], S33, 0x6d9d6122L); /*35*/b= HH(b, c, d, a, x[14], S34, 0xfde5380cL); /*36*/a= HH(a, b, c, d, x[1], S31, 0xa4beea44L); /*37*/d= HH(d, a, b, c, x[4], S32, 0x4bdecfa9L); /*38*/c= HH(c, d, a, b, x[7], S33, 0xf6bb4b60L); /*39*/b= HH(b, c, d, a, x[10], S34, 0xbebfbc70L); /*40*/a= HH(a, b, c, d, x[13], S31, 0x289b7ec6L); /*41*/d= HH(d, a, b, c, x[0], S32, 0xeaa127faL); /*42*/c= HH(c, d, a, b, x[3], S33, 0xd4ef3085L); /*43*/b= HH(b, c, d, a, x[6], S34, 0x4881d05L); /*44*/a= HH(a, b, c, d, x[9], S31, 0xd9d4d039L); /*45*/d= HH(d, a, b, c, x[12], S32, 0xe6db99e5L); /*46*/c= HH(c, d, a, b, x[15], S33, 0x1fa27cf8L); /*47*/b= HH(b, c, d, a, x[2], S34, 0xc4ac5665L); /*48*/

//第4级

a = II(a, b, c, d, x[0], S41, 0xf4292244L); /*49*/d= II(d, a, b, c, x[7], S42, 0x432aff97L); /*50*/c= II(c, d, a, b, x[14], S43, 0xab9423a7L); /*51*/b= II(b, c, d, a, x[5], S44, 0xfc93a039L); /*52*/a= II(a, b, c, d, x[12], S41, 0x655b59c3L); /*53*/d= II(d, a, b, c, x[3], S42, 0x8f0ccc92L); /*54*/c= II(c, d, a, b, x[10], S43, 0xffeff47dL); /*55*/b= II(b, c, d, a, x[1], S44, 0x85845dd1L); /*56*/a= II(a, b, c, d, x[8], S41, 0x6fa87e4fL); /*57*/d= II(d, a, b, c, x[15], S42, 0xfe2ce6e0L); /*58*/c= II(c, d, a, b, x[6], S43, 0xa3014314L); /*59*/b= II(b, c, d, a, x[13], S44, 0x4e0811a1L); /*60*/a= II(a, b, c, d, x[4], S41, 0xf7537e82L); /*61*/d= II(d, a, b, c, x[11], S42, 0xbd3af235L); /*62*/c= II(c, d, a, b, x[2], S43, 0x2ad7d2bbL); /*63*/b= II(b, c, d, a, x[9], S44, 0xeb86d391L); /*64*/

//分别累加到state[0],state[1],state[2],state[3]

state[0] +=a;

state[1] +=b;

state[2] +=c;

state[3] +=d;

}//把byte型数据转换为无符号long型数据

private static long byteToul(byteb)

{return b > 0 ? b : (b & 0x7F + 128);

}//把byte类型的数据转换成十六进制ASCII字符表示

private static String byteToHEX(bytein)

{char[] DigitStr ={'0', '1', '2', '3', '4', '5', '6', '7', '8', '9','A', 'B', 'C', 'D', 'E', 'F'};char[] out = new char[2];

out[0] = DigitStr[(in >> 4) & 0x0F]; //取高4位

out[1] = DigitStr[in & 0x0F]; //取低4位

String s = newString(out);returns;

}//将long型数组按顺序拆成byte型数组,长度为len

private void Encode(byte[] output, long[] input, intlen)

{inti, j;for (i = 0, j = 0; j < len; i++, j += 4)

{

output[j]= (byte) (input[i] & 0xffL);

output[j+ 1] = (byte) ((input[i] >>> 8) & 0xffL);

output[j+ 2] = (byte) ((input[i] >>> 16) & 0xffL);

output[j+ 3] = (byte) ((input[i] >>> 24) & 0xffL);

}

}//将byte型数组按顺序合成long型数组，长度为len

private void Decode(long[] output, byte[] input, intlen)

{inti, j;for (i = 0, j = 0; j < len; i++, j += 4)

{

output[i]=byteToul(input[j])| (byteToul(input[j + 1]) << 8)| (byteToul(input[j + 2]) << 16)| (byteToul(input[j + 3]) << 24);

}

}

}