java实现MD5加密算法

package com.moonights.tools;   
  
public class MD5Encrypt {   
       
    /*  
     *下面这些S11-S44实际上是一个4*4的矩阵，在原始的C实现中是用#define 实现的， 这里把它们实现成为static  
     *final是表示了只读，切能在同一个进程空间内的多个 Instance间共享  
     */  
    private static final int S11 = 7;      
    private static final int S12 = 12;     
    private static final int S13 = 17;     
    private static final int S14 = 22;     
    private static final int S21 = 5;      
    private static final int S22 = 9;      
    private static final int S23 = 14;     
    private static final int S24 = 20;     
    private static final int S31 = 4;      
    private static final int S32 = 11;     
    private static final int S33 = 16;     
    private static final int S34 = 23;     
    private static final int S41 = 6;      
    private static final int S42 = 10;     
    private static final int S43 = 15;     
    private static final int S44 = 21;   
       
    private 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 };   
    /*  
     * 下面的三个成员是MD5计算过程中用到的3个核心数据，在原始的C实现中 被定义到MD5_CTX结构中  
     */  
    private long[] state = new long[4];// state (ABCD)   
    private long[] count = new long[2];// number of bits, modulo 2^64 (lsb// first)   
    private byte[] buffer = new byte[64]; // input buffer   
       
    /*  
     * digestHexStr是MD5的唯一一个公共成员，是最新一次计算结果的 16进制ASCII表示.  
     */  
    private String digestHexStr;   
       
    /*  
     * digest,是最新一次计算结果的2进制内部表示，表示128bit的MD5值.  
     */  
    private byte[] digest = new byte[16];   
       
    //MD5唯一实例;   
    private static MD5Encrypt instance =null;   
       
    /*  
     * 这是MD5这个类的标准构造函数，JavaBean要求有一个public的并且没有参数的构造函数  
     */  
    private MD5Encrypt(){   
        md5Init();   
        return;   
    }   
       
    /*  
     * 返回MD5Encrypt实例  
     */  
    public static MD5Encrypt getInstance(){   
        if(instance == null){   
            instance = new MD5Encrypt();    
        }   
        return instance;   
    }   
       
       
       
    //md5Init是一个初始化函数，初始化核心变量，装入标准的幻数   
    private void md5Init(){   
        count[0] = 0L;   
        count[1] = 0L;   
        //Load magic initialization constants.   
        state[0] = 0x67452301L;   
        state[1] = 0xefcdab89L;   
        state[2] = 0x98badcfeL;   
        state[3] = 0x10325476L;   
        return;   
    }   
       
    /*F, G, H ,I 是4个基本的MD5函数，在原始的MD5的C实现中，由于它们是  
     * 简单的位运算，可能出于效率的考虑把它们实现成了宏，在java中，我们把它们 实现成了private方法，名字保持了原来C中的。  
     */  
    private long F(long x, long y, long z){        
        return (x & y) | ((~x) & z);   
    }   
    private long G(long x, long y, long z){        
        return (x & z) | (y & (~z));   
    }      
    private long H(long x, long y, long z){        
        return x ^ y ^ z;      
    }      
    private long I(long x, long y, long z){        
        return y ^ (x | (~z));     
    }   
       
    /*  
     * FF,GG,HH和II将调用F,G,H,I进行近一步变换 FF, GG, HH, and II transformations for  
     * rounds 1, 2, 3, and 4. Rotation is separate from addition to prevent recomputation.  
     */  
    private long FF(long a, long b, long c, long d, long x, long s, long ac){   
        a += F(b, c, d) + x + ac;   
        a = ((int) a << s) | ((int) a >>> (32 - s));   
        a += b;   
        return a;   
    }   
    private long GG(long a, long b, long c, long d, long x, long s, long ac){   
        a += G(b, c, d) + x + ac;   
        a = ((int) a << s) | ((int) a >>> (32 - s));   
        a += b;   
        return a;   
    }   
    private long HH(long a, long b, long c, long d, long x, long s, long ac){   
        a += H(b, c, d) + x + ac;   
        a = ((int) a << s) | ((int) a >>> (32 - s));   
        a += b;   
        return a;   
    }   
    private long II(long a, long b, long c, long d, long x, long s, long ac){   
        a += I(b, c, d) + x + ac;   
        a = ((int) a << s) | ((int) a >>> (32 - s));   
        a += b;   
        return a;   
    }   
       
    /*  
     * md5Update是MD5的主计算过程，inbuf是要变换的字节串，inputlen是长度，这个  
     * 函数由getMD5ofStr调用，调用之前需要调用md5init，因此把它设计成private的  
     */  
    private void md5Update(byte[] inbuf, int inputLen){   
        int i, index, partLen;   
        byte[] block = new byte[64];   
        index = (int) (count[0] >>> 3) & 0x3F;   
        //Update number of bits    
        if ((count[0] += (inputLen << 3)) < (inputLen << 3))   
            count[1]++;   
        count[1] += (inputLen >>> 29);   
        partLen = 64 - index;   
        //Transform. as many times as possible.   
        if (inputLen >= partLen){   
            md5Memcpy(buffer, inbuf, index, 0, partLen);   
            md5Transform(buffer);   
            for (i = partLen; i + 63 < inputLen; i += 64){   
                md5Memcpy(block, inbuf, 0, i, 64);   
                md5Transform(block);   
            }   
            index = 0;   
        }else{   
            i = 0;   
        }   
        //Buffer remaining input    
        md5Memcpy(buffer, inbuf, index, i, inputLen - i);   
    }   
       
    /*  
     * md5Final整理和填写输出结果  
     */  
    private void md5Final(){   
        byte[] bits = new byte[8];   
        int index, padLen;   
        //Save number of bits    
        Encode(bits, count, 8);   
        //Pad out to 56 mod 64.   
        index = (int) (count[0] >>> 3) & 0x3f;   
        padLen = (index < 56) ? (56 - index) : (120 - index);   
        md5Update(PADDING, padLen);   
        //Append length (before padding)   
        md5Update(bits, 8);   
        //Store state in digest    
        Encode(digest, state, 16);   
    }   
       
    /*  
     * md5Memcpy是一个内部使用的byte数组的块拷贝函数，从input的inpos开始把len长度的  
     * 字节拷贝到output的outpos位置开始  
     */  
    private void md5Memcpy(byte[] output, byte[] input, int outpos, int inpos, int len){   
        int i;   
        for (i = 0; i < len; i++)   
            output[outpos + i] = input[inpos + i];   
    }   
       
    /*  
     * md5Transform是MD5核心变换程序，有md5Update调用，block是分块的原始字节  
     */  
    private void md5Transform(byte block[]){   
        long a = state[0], b = state[1], c = state[2], d = state[3];   
        long[] x = new long[16];   
        Decode(x, block, 64);   
        // Round 1   
        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 */  
        //Round 2   
        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 */  
        //Round 3   
        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 */  
        //Round 4   
        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 */           
        state[0] += a;         
        state[1] += b;         
        state[2] += c;         
        state[3] += d;   
    }   
       
    /*  
     * Encode把long数组按顺序拆成byte数组，因为java的long类型是64bit的，只拆低32bit，以适应原始C实现的用途  
     */  
    private void Encode(byte[] output, long[] input, int len){   
        int i, 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);   
        }   
    }   
       
    /*  
     * Decode把byte数组按顺序合成成long数组，因为java的long类型是64bit的，  
     * 只合成低32bit，高32bit清零，以适应原始C实现的用途  
     */  
    private void Decode(long[] output, byte[] input, int len){   
        int i, j;   
        for (i = 0, j = 0; j < len; i++, j += 4)   
            output[i] = b2iu(input[j]) | (b2iu(input[j + 1]) << 8) | (b2iu(input[j + 2]) << 16) | (b2iu(input[j+3]) << 24);   
        return;   
    }   
       
    /*  
     * b2iu是我写的一个把byte按照不考虑正负号的原则的＂升位＂程序，因为java没有unsigned运算  
     */  
    private static long b2iu(byte b){   
        return b < 0 ? b & 0x7F + 128 : b;   
    }   
       
    /*  
     * byteHEX()，用来把一个byte类型的数转换成十六进制的ASCII表示，  
     * 因为java中的byte的toString无法实现这一点，我们又没有C语言中的 sprintf(outbuf,"%02X",ib)  
     */  
    private static String byteHEX(byte ib){   
        char[] Digit = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A','B', 'C', 'D', 'E', 'F' };   
        char[] b = new char[2];        
        ob[0] = Digit[(ib >>> 4) & 0X0F];         
        ob[1] = Digit[ib & 0X0F];          
        String s = new String(ob);         
        return s;   
    }   
       
    /*  
     * encrypt是类MD5最主要的公共方法，入口参数是你想要进行MD5变换的字符串  
     * 返回的是变换完的结果，这个结果是从公共成员digestHexStr取得的．  
     */  
    public String encrypt(String inbuf){   
        md5Init();   
        md5Update(inbuf.getBytes(), inbuf.length());   
        md5Final();   
        digestHexStr = "";   
        for (int i = 0; i < 16; i++) {   
            digestHexStr += byteHEX(digest[i]);   
        }   
        return digestHexStr;   
    }   
       
    /*  
     * 测试  
     */  
    public static void main(String[] args){   
        System.out.println(MD5Encrypt.getInstance().encrypt("TestPassword"));      
    }   
}