MD5算法是将資料進行不可逆加密的算法有較好的安全性，在國内如壽信的安全支付平台就采用此算法。
源代碼如下
import java.lang.reflect.*;
public class MD5 {
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 };
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
public String digestHexStr;
private byte[] digest = new byte[16];
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;
}
// 這是MD5這個類的标準構造函數，JavaBean要求有一個public的并且沒有參數的構造函數
public MD5() {
md5Init();
return;
}
private void md5Init() {
count[0] = 0L;
count[1] = 0L;
//
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));
}
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;
}
private void md5Update(byte[] inbuf, int inputLen) {
int i, index, partLen;
byte[] block = new byte[64];
index = (int)(count[0] >>> 3) & 0x3F;
//
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;
//
md5Memcpy(buffer, inbuf, index, i, inputLen - i);
}
private void md5Final () {
byte[] bits = new byte[8];
int index, padLen;
//
Encode (bits, count, 8);
//
md5Update(bits, 8);
//
Encode (digest, state, 16);
}
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];
}
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);
a = FF (a, b, c, d, x[0], S11, 0xd76aa478L);
d = FF (d, a, b, c, x[1], S12, 0xe8c7b756L);
c = FF (c, d, a, b, x[2], S13, 0x242070dbL);
b = FF (b, c, d, a, x[3], S14, 0xc1bdceeeL);
a = FF (a, b, c, d, x[4], S11, 0xf57c0fafL);
d = FF (d, a, b, c, x[5], S12, 0x4787c62aL);
c = FF (c, d, a, b, x[6], S13, 0xa8304613L);
b = FF (b, c, d, a, x[7], S14, 0xfd469501L);
a = FF (a, b, c, d, x[8], S11, 0x698098d8L);
d = FF (d, a, b, c, x[9], S12, 0x8b44f7afL);
c = FF (c, d, a, b, x[10], S13, 0xffff5bb1L);
b = FF (b, c, d, a, x[11], S14, 0x895cd7beL);
a = FF (a, b, c, d, x[12], S11, 0x6b901122L);
d = FF (d, a, b, c, x[13], S12, 0xfd987193L);
c = FF (c, d, a, b, x[14], S13, 0xa679438eL);
b = FF (b, c, d, a, x[15], S14, 0x49b40821L);
a = GG (a, b, c, d, x[1], S21, 0xf61e2562L);
d = GG (d, a, b, c, x[6], S22, 0xc040b340L);
c = GG (c, d, a, b, x[11], S23, 0x265e5a51L);
b = GG (b, c, d, a, x[0], S24, 0xe9b6c7aaL);
a = GG (a, b, c, d, x[5], S21, 0xd62f105dL);
d = GG (d, a, b, c, x[10], S22, 0x2441453L);
c = GG (c, d, a, b, x[15], S23, 0xd8a1e681L);
b = GG (b, c, d, a, x[4], S24, 0xe7d3fbc8L);
a = GG (a, b, c, d, x[9], S21, 0x21e1cde6L);
d = GG (d, a, b, c, x[14], S22, 0xc33707d6L);
c = GG (c, d, a, b, x[3], S23, 0xf4d50d87L);
b = GG (b, c, d, a, x[8], S24, 0x455a14edL);
a = GG (a, b, c, d, x[13], S21, 0xa9e3e905L);
d = GG (d, a, b, c, x[2], S22, 0xfcefa3f8L);
c = GG (c, d, a, b, x[7], S23, 0x676f02d9L);
b = GG (b, c, d, a, x[12], S24, 0x8d2a4c8aL);
a = HH (a, b, c, d, x[5], S31, 0xfffa3942L);
d = HH (d, a, b, c, x[8], S32, 0x8771f681L);
c = HH (c, d, a, b, x[11], S33, 0x6d9d6122L);
b = HH (b, c, d, a, x[14], S34, 0xfde5380cL);
a = HH (a, b, c, d, x[1], S31, 0xa4beea44L);
d = HH (d, a, b, c, x[4], S32, 0x4bdecfa9L);
c = HH (c, d, a, b, x[7], S33, 0xf6bb4b60L);
b = HH (b, c, d, a, x[10], S34, 0xbebfbc70L);
a = HH (a, b, c, d, x[13], S31, 0x289b7ec6L);
d = HH (d, a, b, c, x[0], S32, 0xeaa127faL);
c = HH (c, d, a, b, x[3], S33, 0xd4ef3085L);
b = HH (b, c, d, a, x[6], S34, 0x4881d05L);
a = HH (a, b, c, d, x[9], S31, 0xd9d4d039L);
d = HH (d, a, b, c, x[12], S32, 0xe6db99e5L);
c = HH (c, d, a, b, x[15], S33, 0x1fa27cf8L);
b = HH (b, c, d, a, x[2], S34, 0xc4ac5665L);
a = II (a, b, c, d, x[0], S41, 0xf4292244L);
d = II (d, a, b, c, x[7], S42, 0x432aff97L);
c = II (c, d, a, b, x[14], S43, 0xab9423a7L);
b = II (b, c, d, a, x[5], S44, 0xfc93a039L);
a = II (a, b, c, d, x[12], S41, 0x655b59c3L);
d = II (d, a, b, c, x[3], S42, 0x8f0ccc92L);
c = II (c, d, a, b, x[10], S43, 0xffeff47dL);
b = II (b, c, d, a, x[1], S44, 0x85845dd1L);
a = II (a, b, c, d, x[8], S41, 0x6fa87e4fL);
d = II (d, a, b, c, x[15], S42, 0xfe2ce6e0L);
c = II (c, d, a, b, x[6], S43, 0xa3014314L);
b = II (b, c, d, a, x[13], S44, 0x4e0811a1L);
a = II (a, b, c, d, x[4], S41, 0xf7537e82L);
d = II (d, a, b, c, x[11], S42, 0xbd3af235L);
c = II (c, d, a, b, x[2], S43, 0x2ad7d2bbL);
b = II (b, c, d, a, x[9], S44, 0xeb86d391L);
state[0] += a;
state[1] += b;
state[2] += c;
state[3] += d;
}
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);
}
}
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;
}
public static long b2iu(byte b) {
return b < 0 ? b & 0x7F + 128 : 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) & 0X0F];
ob[1] = Digit[ib & 0X0F];
String s = new String(ob);
return s;
}
}