java 关于MD5加密

现在很多时候会用到md5加密的技术，其实很简单就是不管是什么字符串通过md5加密之后都会生成一个别人很难识别的长字符串，也就是密文，MD5也算一个常用的工具类了，大家可以下载

package com.weibao.util.secret;

import java.util.Arrays;

import com.weibao.util.secret.DataChange;

/*************************************************
* 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 {
String hex_chr = "0123456789abcdef";

private byte[] key;

public MD5() {
// TODO Auto-generated constructor stub
this.key = new byte[16];
this.key[0] = (byte) 0x11;
this.key[1] = (byte) 0x22;
this.key[2] = (byte) 0x33;
this.key[3] = (byte) 0x44;
this.key[4] = (byte) 0x55;
this.key[5] = (byte) 0x66;
this.key[6] = (byte) 0x77;
this.key[7] = (byte) 0x88;
this.key[8] = (byte) 0x99;
this.key[9] = (byte) 0x00;
this.key[10] = (byte) 0xaa;
this.key[11] = (byte) 0xbb;
this.key[12] = (byte) 0xcc;
this.key[13] = (byte) 0xdd;
this.key[14] = (byte) 0xee;
this.key[15] = (byte) 0xff;
}

public MD5(byte[] key) {
this.key = key;
}

public String hex(byte[] arr) {
String str = "";
for (int i = 0; i < arr.length; i++)
str = str + hex_chr.charAt((arr[i] >> 4) & 0x0F)
+ hex_chr.charAt(arr[i] & 0x0F);
return str;
}

/*
* Add integers, wrapping at 2^32
*/
private int add(int x, int y) {
return ((x & 0x7FFFFFFF) + (y & 0x7FFFFFFF)) ^ (x & 0x80000000)
^ (y & 0x80000000);
}

/*
* Bitwise rotate a 32-bit number to the left
*/
private int rol(int num, int cnt) {
return (num << cnt) | (num >>> (32 - cnt));
}

/*
* These functions implement the basic operation for each round of the
* algorithm.
*/
private int cmn(int q, int a, int b, int x, int s, int t) {
return add(rol(add(add(a, q), add(x, t)), s), b);
}

private int ff(int a, int b, int c, int d, int x, int s, int t) {
return cmn((b & c) | ((~b) & d), a, b, x, s, t);
}

private int gg(int a, int b, int c, int d, int x, int s, int t) {
return cmn((b & d) | (c & (~d)), a, b, x, s, t);
}

private int hh(int a, int b, int c, int d, int x, int s, int t) {
return cmn(b ^ c ^ d, a, b, x, s, t);
}

private int ii(int a, int b, int c, int d, int x, int s, int t) {
return cmn(c ^ (b | (~d)), a, b, x, s, t);
}

/*
* Convert a byte array to a sequence of 16-word blocks, stored as an array.
* Append padding bits and the length, as described in the MD5 standard.
*/

private int[] str2blks_MD5(byte[] str) {
int nblk = ((str.length + 8) >> 6) + 1;
int[] blks = new int[nblk * 16];
int i = 0;
for (i = 0; i < nblk * 16; i++) {
blks[i] = 0;
}
for (i = 0; i < str.length; i++) {
blks[i >> 2] |= (str[i] & 0xFF) << ((i % 4) * 8);
}
blks[i >> 2] |= 0x80 << ((i % 4) * 8);
blks[nblk * 16 - 2] = str.length * 8;

return blks;
}

public byte[] calcMD5(byte[] str, byte[] key) {
byte[] mac = new byte[16];

int[] x = str2blks_MD5(str);

/*
* java initial vector : a = 0x67452301 b = 0xEFCDAB89 c = 0x98BADCFE d
* = 0x01325476
*/

int a = (((key[3] & 0xFF) << 24) | ((key[2] & 0xFF) << 16)
| ((key[1] & 0xFF) << 8) | (key[0] & 0xFF));
int b = (((key[7] & 0xFF) << 24) | ((key[6] & 0xFF) << 16)
| ((key[5] & 0xFF) << 8) | (key[4] & 0xFF));
int c = (((key[11] & 0xFF) << 24) | ((key[10] & 0xFF) << 16)
| ((key[9] & 0xFF) << 8) | (key[8] & 0xFF));
int d = (((key[15] & 0xFF) << 24) | ((key[14] & 0xFF) << 16)
| ((key[13] & 0xFF) << 8) | (key[12] & 0xFF));

for (int i = 0; i < x.length; i += 16) {
int olda = a;
int oldb = b;
int oldc = c;
int oldd = d;

a = ff(a, b, c, d, x[i + 0], 7, 0xD76AA478);
d = ff(d, a, b, c, x[i + 1], 12, 0xE8C7B756);
c = ff(c, d, a, b, x[i + 2], 17, 0x242070DB);
b = ff(b, c, d, a, x[i + 3], 22, 0xC1BDCEEE);
a = ff(a, b, c, d, x[i + 4], 7, 0xF57C0FAF);
d = ff(d, a, b, c, x[i + 5], 12, 0x4787C62A);
c = ff(c, d, a, b, x[i + 6], 17, 0xA8304613);
b = ff(b, c, d, a, x[i + 7], 22, 0xFD469501);
a = ff(a, b, c, d, x[i + 8], 7, 0x698098D8);
d = ff(d, a, b, c, x[i + 9], 12, 0x8B44F7AF);
c = ff(c, d, a, b, x[i + 10], 17, 0xFFFF5BB1);
b = ff(b, c, d, a, x[i + 11], 22, 0x895CD7BE);
a = ff(a, b, c, d, x[i + 12], 7, 0x6B901122);
d = ff(d, a, b, c, x[i + 13], 12, 0xFD987193);
c = ff(c, d, a, b, x[i + 14], 17, 0xA679438E);
b = ff(b, c, d, a, x[i + 15], 22, 0x49B40821);

a = gg(a, b, c, d, x[i + 1], 5, 0xF61E2562);
d = gg(d, a, b, c, x[i + 6], 9, 0xC040B340);
c = gg(c, d, a, b, x[i + 11], 14, 0x265E5A51);
b = gg(b, c, d, a, x[i + 0], 20, 0xE9B6C7AA);
a = gg(a, b, c, d, x[i + 5], 5, 0xD62F105D);
d = gg(d, a, b, c, x[i + 10], 9, 0x02441453);
c = gg(c, d, a, b, x[i + 15], 14, 0xD8A1E681);
b = gg(b, c, d, a, x[i + 4], 20, 0xE7D3FBC8);
a = gg(a, b, c, d, x[i + 9], 5, 0x21E1CDE6);
d = gg(d, a, b, c, x[i + 14], 9, 0xC33707D6);
c = gg(c, d, a, b, x[i + 3], 14, 0xF4D50D87);
b = gg(b, c, d, a, x[i + 8], 20, 0x455A14ED);
a = gg(a, b, c, d, x[i + 13], 5, 0xA9E3E905);
d = gg(d, a, b, c, x[i + 2], 9, 0xFCEFA3F8);
c = gg(c, d, a, b, x[i + 7], 14, 0x676F02D9);
b = gg(b, c, d, a, x[i + 12], 20, 0x8D2A4C8A);

a = hh(a, b, c, d, x[i + 5], 4, 0xFFFA3942);
d = hh(d, a, b, c, x[i + 8], 11, 0x8771F681);
c = hh(c, d, a, b, x[i + 11], 16, 0x6D9D6122);
b = hh(b, c, d, a, x[i + 14], 23, 0xFDE5380C);
a = hh(a, b, c, d, x[i + 1], 4, 0xA4BEEA44);
d = hh(d, a, b, c, x[i + 4], 11, 0x4BDECFA9);
c = hh(c, d, a, b, x[i + 7], 16, 0xF6BB4B60);
b = hh(b, c, d, a, x[i + 10], 23, 0xBEBFBC70);
a = hh(a, b, c, d, x[i + 13], 4, 0x289B7EC6);
d = hh(d, a, b, c, x[i + 0], 11, 0xEAA127FA);
c = hh(c, d, a, b, x[i + 3], 16, 0xD4EF3085);
b = hh(b, c, d, a, x[i + 6], 23, 0x04881D05);
a = hh(a, b, c, d, x[i + 9], 4, 0xD9D4D039);
d = hh(d, a, b, c, x[i + 12], 11, 0xE6DB99E5);
c = hh(c, d, a, b, x[i + 15], 16, 0x1FA27CF8);
b = hh(b, c, d, a, x[i + 2], 23, 0xC4AC5665);

a = ii(a, b, c, d, x[i + 0], 6, 0xF4292244);
d = ii(d, a, b, c, x[i + 7], 10, 0x432AFF97);
c = ii(c, d, a, b, x[i + 14], 15, 0xAB9423A7);
b = ii(b, c, d, a, x[i + 5], 21, 0xFC93A039);
a = ii(a, b, c, d, x[i + 12], 6, 0x655B59C3);
d = ii(d, a, b, c, x[i + 3], 10, 0x8F0CCC92);
c = ii(c, d, a, b, x[i + 10], 15, 0xFFEFF47D);
b = ii(b, c, d, a, x[i + 1], 21, 0x85845DD1);
a = ii(a, b, c, d, x[i + 8], 6, 0x6FA87E4F);
d = ii(d, a, b, c, x[i + 15], 10, 0xFE2CE6E0);
c = ii(c, d, a, b, x[i + 6], 15, 0xA3014314);
b = ii(b, c, d, a, x[i + 13], 21, 0x4E0811A1);
a = ii(a, b, c, d, x[i + 4], 6, 0xF7537E82);
d = ii(d, a, b, c, x[i + 11], 10, 0xBD3AF235);
c = ii(c, d, a, b, x[i + 2], 15, 0x2AD7D2BB);
b = ii(b, c, d, a, x[i + 9], 21, 0xEB86D391);

a = add(a, olda);
b = add(b, oldb);
c = add(c, oldc);
d = add(d, oldd);
}

mac[0] = (byte) ((a >> 0) & 0xFF);
mac[1] = (byte) ((a >> 8) & 0xFF);
mac[2] = (byte) ((a >> 16) & 0xFF);
mac[3] = (byte) ((a >> 24) & 0xFF);
mac[4] = (byte) ((b >> 0) & 0xFF);
mac[5] = (byte) ((b >> 8) & 0xFF);
mac[6] = (byte) ((b >> 16) & 0xFF);
mac[7] = (byte) ((b >> 24) & 0xFF);
mac[8] = (byte) ((c >> 0) & 0xFF);
mac[9] = (byte) ((c >> 8) & 0xFF);
mac[10] = (byte) ((c >> 16) & 0xFF);
mac[11] = (byte) ((c >> 24) & 0xFF);
mac[12] = (byte) ((d >> 0) & 0xFF);
mac[13] = (byte) ((d >> 8) & 0xFF);
mac[14] = (byte) ((d >> 16) & 0xFF);
mac[15] = (byte) ((d >> 24) & 0xFF);

return mac;
}

public byte[] calcMD5(byte[] str) {
return calcMD5(str, key);
}

public byte[] calcMD5(String str) {
byte[] buffer = DataChange.Unicode2Byte(str);
return calcMD5(buffer);
}

/*
* 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 byte[] getSubBytes(byte[] original, int newLength) {

if (original.length >= newLength) {
return Arrays.copyOf(original, newLength);
} else {
byte[] newBytes = new byte[newLength];
for (int i = 0; i < original.length; i++) {
newBytes[newLength - original.length + i] = original[i];
}
return newBytes;
}
}

/**
*
* @作者 庄小达
* @编写日期 2015-11-13
* @功能描述 通用加密字符串
*
* @返回值 byte[]
* @参数
*/
public String encrypt(String str){
return hex(calcMD5(str));
}

public String encrypt(byte[] b){
return hex(calcMD5(b));
}

}

其中encrypt()方法是加密用的，大家可以new一个MD5出来就好。MD5 md = new MD%(); md.encrypt("你想要加密的内容");

一般数据库存的密码是通过MD5密文加密后放入数据库，比对的时候加密后比对加密后是否equls()就ok了。安全考虑。

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