MD5加密源码有几处看不懂的求讲解

[Mooner_guo]

update()方法喔就不知道要干嘛，还有就是这个是怎么存储的？分割和填充部分看不懂！！看的好乱啊！~
//package bignum;
import static java.lang.System.*;
///MD5加密算法java实现
import java.lang.reflect.*;
/*************************************************
md5 类实现了RSA Data Security, Inc.在提交给IETF
的RFC1321中的MD5 message-digest 算法。
*************************************************/

public class MD5 {
/* 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*/
static final int S11 = 7;
static final int S12 = 12;
static final int S13 = 17;
static final int S14 = 22;

static final int S21 = 5;
static final int S22 = 9;
static final int S23 = 14;
static final int S24 = 20;

static final int S31 = 4;
static final int S32 = 11;
static final int S33 = 16;
static final int S34 = 23;

static final int S41 = 6;
static final int S42 = 10;
static final int S43 = 15;
static final int S44 = 21;

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.
*/
public 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];

/*
getMD5ofStr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 getMD5ofStr(String inbuf) {
md5Init();
md5Update(inbuf.getBytes(), inbuf.length());
md5Final();
digestHexStr = "";
for (int i = 0; i < 16; i++) {
digestHexStr += byteHEX(digest[i]);
}
return digestHexStr;

}

[Mooner_guo]

// 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 public MD5() { md5Init(); return; } /* 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, //ac 为随机数，x为16个子分组,s为随机数Ti long ac) { // a += F (b, c, d) + x + ac; // a = ((int) a << s) | ((int) a >>> (32 - s)); // a += b; a = (F(b, c, d) + x + ac ) << s + 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; a = (G (b, c, d) + x + ac ) << s + 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; a = (H(b, c, d) + x + ac ) << s + 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; a = (I(b, c, d) + x + ac ) << s + 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]; //64 * byte为512位 index = (int)(count[0] >>> 3) & 0x3F; out.println("cout[0] >>> 3 = " + (count[0] >>> 3)); // /* Update number of bits */ if ((count[0] += (inputLen << 3)) < (inputLen << 3)) count[1]++; count[1] += (inputLen >>> 29); out.println("cout[0] = " + count[0] + "count[1] = " + count[1]); partLen = 64 - index; out.println("partLen = " + partLen); // 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; //0x3f = 63(10) 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]; }

[Mooner_guo]

/* 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 */ public 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) */ public static String byteHEX(byte ib) { char[] Digit = { '0','1','2','3','4','5','6','7','8','9', 'A','B','C','D','E','F' }; char [] ob = new char[2]; ob[0] = Digit[(ib >>> 4) & 0X0F]; ob[1] = Digit[ib & 0X0F]; String s = new String(ob); return s; } public static void main(String args[]) { MD5 m = new MD5(); if (Array.getLength(args) == 0) { //如果没有参数，执行标准的Test Suite System.out.println("MD5 Test suite:"); System.out.println("MD5(\"\"):"+m.getMD5ofStr("")); System.out.println("MD5(\"我了个去\"):"+m.getMD5ofStr("我了个去")); System.out.println("MD5(\"a\"):"+m.getMD5ofStr("a")); System.out.println("MD5(\"abc\"):"+m.getMD5ofStr("abc")); System.out.println("MD5(\"message digest\"):"+m.getMD5ofStr("message digest")); System.out.println("MD5(\"abcdefghijklmnopqrstuvwxyz\"):"+ m.getMD5ofStr("abcdefghijklmnopqrstuvwxyz")); System.out.println("MD5(\"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789\"):"+ m.getMD5ofStr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789")); } else System.out.println("MD5(" + args[0] + ")=" + m.getMD5ofStr(args[0])); } }