MD5的全称是Message-Digest Algorithm 5(信息-摘要算法),作用是让大容量信息在用数字签名软件签署私人密匙前被"压缩"成一种保密的格式(就是把一个任意长度的字节串变换成一定长的大整数)。不管是MD2、MD4还是MD5,它们都需要获得一个随机长度的信息并产生一个128位的信息摘要。虽然这些算法的结构或多或少有些相似,但MD2的设计与MD4和MD5完全不同,那是因为MD2是为8位机器做过设计优化的,而MD4和MD5却是面向32位的电脑。
下面这个类是md5算法的实现过程:
import java.lang.reflect.Array;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class MD5Encrypter {
//下面是个4*4的矩阵
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
*/
private long[] state = new long[4];
private long[] count = new long[2];
private byte[] buffer = new byte[64];
//最新一次计算结果的16进制ASCII表示
public String digestHexStr;
//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];
private static MD5Encrypter md5 = new MD5Encrypter();
//加密函数,str为需加密的字符串,返回加密过的字符串
public String encrypt(String str){
if(str==null){
return null;
}
md5Init();
md5Update(str.getBytes(), str.length());
md5Final();
this.digestHexStr = "";
for (int i = 0; i < 16; i++) {
this.digestHexStr += byteHEX(this.digest[i]);
}
return digestHexStr;
}
public String getMD5ofStr(String inbuf) {
md5Init();
md5Update(inbuf.getBytes(), inbuf.length());
md5Final();
this.digestHexStr = "";
for (int i = 0; i < 8; ++i) {
this.digestHexStr += byteHEX(this.digest[i]);
}
return this.digestHexStr.substring(0, 11);
}
public String getMD5to16(String param) throws NoSuchAlgorithmException {
return jdkmd5(param).substring(8, 24);
}
public String getMD5to32(String param) throws NoSuchAlgorithmException {
return jdkmd5(param);
}
private String jdkmd5(String param) throws NoSuchAlgorithmException {
try {
MessageDigest md5 = MessageDigest.getInstance("MD5");
md5.update(param.getBytes());
byte[] b = md5.digest();
StringBuffer buf = new StringBuffer("");
for (int offset = 0; offset < b.length; ++offset) {
int i = b[offset];
if (i < 0)
i += 256;
if (i < 16)
buf.append("0");
buf.append(Integer.toHexString(i));
}
return buf.toString();
} catch (NoSuchAlgorithmException nsae) {
throw nsae;
}
}
private MD5Encrypter() {
md5Init();
}
public static MD5Encrypter getInstance() {
return md5;
}
private void md5Init() {
this.count[0] = 0L;
this.count[1] = 0L;
this.state[0] = 1732584193L;
this.state[1] = 4023233417L;
this.state[2] = 2562383102L;
this.state[3] = 271733878L;
}
/**
* F,G,H,I 是四个基本的MD5函数
* @param x
* @param y
* @param z
* @return
*/
private long F(long x, long y, long z) {
return (x & y | (x ^ 0xFFFFFFFF) & z);
}
private long G(long x, long y, long z) {
return (x & z | y & (z ^ 0xFFFFFFFF));
}
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 ^ 0xFFFFFFFF));
}
/**
* FF,GG,HH,II将调用F,G,H,I进行进一步变换
*/
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 << (int) s | (int) a >>> (int) (32L - 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 << (int) s | (int) a >>> (int) (32L - 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 << (int) s | (int) a >>> (int) (32L - 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 << (int) s | (int) a >>> (int) (32L - s);
a += b;
return a;
}
//MD5住计算过程
private void md5Update(byte[] inbuf, int inputLen) {
byte[] block = new byte[64];
int index = (int) (this.count[0] >>> 3) & 0x3F;
if ((this.count[0] += (inputLen << 3)) < (inputLen << 3))
this.count[1] += 1L;
this.count[1] += (inputLen >>> 29);
int partLen = 64 - index;
int i;
if (inputLen >= partLen) {
md5Memcpy(this.buffer, inbuf, index, 0, partLen);
md5Transform(this.buffer);
for (i = partLen; i + 63 < inputLen; i += 64) {
md5Memcpy(block, inbuf, 0, i, 64);
md5Transform(block);
}
index = 0;
} else {
i = 0;
}
md5Memcpy(this.buffer, inbuf, index, i, inputLen - i);
}
private void md5Final() {
byte[] bits = new byte[8];
Encode(bits, this.count, 8);
int index = (int) (this.count[0] >>> 3) & 0x3F;
int padLen = (index < 56) ? 56 - index : 120 - index;
md5Update(PADDING, padLen);
md5Update(bits, 8);
Encode(this.digest, this.state, 16);
}
private void md5Memcpy(byte[] output, byte[] input, int outpos, int inpos,
int len) {
for (int i = 0; i < len; ++i)
output[(outpos + i)] = input[(inpos + i)];
}
private void md5Transform(byte[] block) {
long a = this.state[0];
long b = this.state[1];
long c = this.state[2];
long d = this.state[3];
long[] x = new long[16];
Decode(x, block, 64);
a = FF(a, b, c, d, x[0], 7L, 3614090360L);
d = FF(d, a, b, c, x[1], 12L, 3905402710L);
c = FF(c, d, a, b, x[2], 17L, 606105819L);
b = FF(b, c, d, a, x[3], 22L, 3250441966L);
a = FF(a, b, c, d, x[4], 7L, 4118548399L);
d = FF(d, a, b, c, x[5], 12L, 1200080426L);
c = FF(c, d, a, b, x[6], 17L, 2821735955L);
b = FF(b, c, d, a, x[7], 22L, 4249261313L);
a = FF(a, b, c, d, x[8], 7L, 1770035416L);
d = FF(d, a, b, c, x[9], 12L, 2336552879L);
c = FF(c, d, a, b, x[10], 17L, 4294925233L);
b = FF(b, c, d, a, x[11], 22L, 2304563134L);
a = FF(a, b, c, d, x[12], 7L, 1804603682L);
d = FF(d, a, b, c, x[13], 12L, 4254626195L);
c = FF(c, d, a, b, x[14], 17L, 2792965006L);
b = FF(b, c, d, a, x[15], 22L, 1236535329L);
a = GG(a, b, c, d, x[1], 5L, 4129170786L);
d = GG(d, a, b, c, x[6], 9L, 3225465664L);
c = GG(c, d, a, b, x[11], 14L, 643717713L);
b = GG(b, c, d, a, x[0], 20L, 3921069994L);
a = GG(a, b, c, d, x[5], 5L, 3593408605L);
d = GG(d, a, b, c, x[10], 9L, 38016083L);
c = GG(c, d, a, b, x[15], 14L, 3634488961L);
b = GG(b, c, d, a, x[4], 20L, 3889429448L);
a = GG(a, b, c, d, x[9], 5L, 568446438L);
d = GG(d, a, b, c, x[14], 9L, 3275163606L);
c = GG(c, d, a, b, x[3], 14L, 4107603335L);
b = GG(b, c, d, a, x[8], 20L, 1163531501L);
a = GG(a, b, c, d, x[13], 5L, 2850285829L);
d = GG(d, a, b, c, x[2], 9L, 4243563512L);
c = GG(c, d, a, b, x[7], 14L, 1735328473L);
b = GG(b, c, d, a, x[12], 20L, 2368359562L);
a = HH(a, b, c, d, x[5], 4L, 4294588738L);
d = HH(d, a, b, c, x[8], 11L, 2272392833L);
c = HH(c, d, a, b, x[11], 16L, 1839030562L);
b = HH(b, c, d, a, x[14], 23L, 4259657740L);
a = HH(a, b, c, d, x[1], 4L, 2763975236L);
d = HH(d, a, b, c, x[4], 11L, 1272893353L);
c = HH(c, d, a, b, x[7], 16L, 4139469664L);
b = HH(b, c, d, a, x[10], 23L, 3200236656L);
a = HH(a, b, c, d, x[13], 4L, 681279174L);
d = HH(d, a, b, c, x[0], 11L, 3936430074L);
c = HH(c, d, a, b, x[3], 16L, 3572445317L);
b = HH(b, c, d, a, x[6], 23L, 76029189L);
a = HH(a, b, c, d, x[9], 4L, 3654602809L);
d = HH(d, a, b, c, x[12], 11L, 3873151461L);
c = HH(c, d, a, b, x[15], 16L, 530742520L);
b = HH(b, c, d, a, x[2], 23L, 3299628645L);
a = II(a, b, c, d, x[0], 6L, 4096336452L);
d = II(d, a, b, c, x[7], 10L, 1126891415L);
c = II(c, d, a, b, x[14], 15L, 2878612391L);
b = II(b, c, d, a, x[5], 21L, 4237533241L);
a = II(a, b, c, d, x[12], 6L, 1700485571L);
d = II(d, a, b, c, x[3], 10L, 2399980690L);
c = II(c, d, a, b, x[10], 15L, 4293915773L);
b = II(b, c, d, a, x[1], 21L, 2240044497L);
a = II(a, b, c, d, x[8], 6L, 1873313359L);
d = II(d, a, b, c, x[15], 10L, 4264355552L);
c = II(c, d, a, b, x[6], 15L, 2734768916L);
b = II(b, c, d, a, x[13], 21L, 1309151649L);
a = II(a, b, c, d, x[4], 6L, 4149444226L);
d = II(d, a, b, c, x[11], 10L, 3174756917L);
c = II(c, d, a, b, x[2], 15L, 718787259L);
b = II(b, c, d, a, x[9], 21L, 3951481745L);
this.state[0] += a;
this.state[1] += b;
this.state[2] += c;
this.state[3] += d;
}
private void Encode(byte[] output, long[] input, int len) {
int i = 0;
for (int j = 0; j < len; j += 4) {
output[j] = (byte) (int) (input[i] & 0xFF);
output[(j + 1)] = (byte) (int) (input[i] >>> 8 & 0xFF);
output[(j + 2)] = (byte) (int) (input[i] >>> 16 & 0xFF);
output[(j + 3)] = (byte) (int) (input[i] >>> 24 & 0xFF);
++i;
}
}
private void Decode(long[] output, byte[] input, int len) {
int i = 0;
for (int j = 0; j < len; j += 4) {
output[i] = (b2iu(input[j]) | b2iu(input[(j + 1)]) << 8
| b2iu(input[(j + 2)]) << 16 | b2iu(input[(j + 3)]) << 24);
++i;
}
}
public static long b2iu(byte b) {
return b;
}
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 & 0xF)];
ob[1] = Digit[(ib & 0xF)];
String s = new String(ob);
return s;
}
public static void main(String[] args) {
MD5Encrypter m = new MD5Encrypter();
if (Array.getLength(args) == 0) {
System.out.println("MD5 Test suite:");
System.out.println("MD5(\"\"):" + m.getMD5ofStr(""));
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]));
}
try {
System.out.println(m.getMD5to32("000000"));
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
}
}