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 stubthis.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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