MD5加密算法（java及js）

为了防止用户登陆过程中信息被拦截导致信息泄露，我们应该在客户端就对用户密码进行加密。浏览器提交给服务器的是加密后的信息，即使被恶意拦截，被拦截信息也已做了加密处理，现在比较安全的一种加密算法是MD5加密算法，尽管MD5是一种单向的加密算法，但网上也有破解网站，所以为了进一步提高安全性，可以进行两次md5加密，或者结合其他的加密方法如3des等进行二次加密。

代码如下：

js版：

var hexcase = 0;
function hex_md5(a) {
	if (a == "")
		return a;
	return rstr2hex(rstr_md5(str2rstr_utf8(a)))
}
function hex_hmac_md5(a, b) {
	return rstr2hex(rstr_hmac_md5(str2rstr_utf8(a), str2rstr_utf8(b)))
}
function md5_vm_test() {
	return hex_md5("abc").toLowerCase() == "900150983cd24fb0d6963f7d28e17f72"
}
function rstr_md5(a) {
	return binl2rstr(binl_md5(rstr2binl(a), a.length * 8))
}
function rstr_hmac_md5(c, f) {
	var e = rstr2binl(c);
	if (e.length > 16) {
		e = binl_md5(e, c.length * 8)
	}
	var a = Array(16), d = Array(16);
	for ( var b = 0; b < 16; b++) {
		a[b] = e[b] ^ 909522486;
		d[b] = e[b] ^ 1549556828
	}
	var g = binl_md5(a.concat(rstr2binl(f)), 512 + f.length * 8);
	return binl2rstr(binl_md5(d.concat(g), 512 + 128))
}
function rstr2hex(c) {
	try {
		hexcase
	} catch (g) {
		hexcase = 0
	}
	var f = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
	var b = "";
	var a;
	for ( var d = 0; d < c.length; d++) {
		a = c.charCodeAt(d);
		b += f.charAt((a >>> 4) & 15) + f.charAt(a & 15)
	}
	return b
}
function str2rstr_utf8(c) {
	var b = "";
	var d = -1;
	var a, e;
	while (++d < c.length) {
		a = c.charCodeAt(d);
		e = d + 1 < c.length ? c.charCodeAt(d + 1) : 0;
		if (55296 <= a && a <= 56319 && 56320 <= e && e <= 57343) {
			a = 65536 + ((a & 1023) << 10) + (e & 1023);
			d++
		}
		if (a <= 127) {
			b += String.fromCharCode(a)
		} else {
			if (a <= 2047) {
				b += String
						.fromCharCode(192 | ((a >>> 6) & 31), 128 | (a & 63))
			} else {
				if (a <= 65535) {
					b += String.fromCharCode(224 | ((a >>> 12) & 15),
							128 | ((a >>> 6) & 63), 128 | (a & 63))
				} else {
					if (a <= 2097151) {
						b += String.fromCharCode(240 | ((a >>> 18) & 7),
								128 | ((a >>> 12) & 63),
								128 | ((a >>> 6) & 63), 128 | (a & 63))
					}
				}
			}
		}
	}
	return b
}
function rstr2binl(b) {
	var a = Array(b.length >> 2);
	for ( var c = 0; c < a.length; c++) {
		a[c] = 0
	}
	for ( var c = 0; c < b.length * 8; c += 8) {
		a[c >> 5] |= (b.charCodeAt(c / 8) & 255) << (c % 32)
	}
	return a
}
function binl2rstr(b) {
	var a = "";
	for ( var c = 0; c < b.length * 32; c += 8) {
		a += String.fromCharCode((b[c >> 5] >>> (c % 32)) & 255)
	}
	return a
}
function binl_md5(p, k) {
	p[k >> 5] |= 128 << ((k) % 32);
	p[(((k + 64) >>> 9) << 4) + 14] = k;
	var o = 1732584193;
	var n = -271733879;
	var m = -1732584194;
	var l = 271733878;
	for ( var g = 0; g < p.length; g += 16) {
		var j = o;
		var h = n;
		var f = m;
		var e = l;
		o = md5_ff(o, n, m, l, p[g + 0], 7, -680876936);
		l = md5_ff(l, o, n, m, p[g + 1], 12, -389564586);
		m = md5_ff(m, l, o, n, p[g + 2], 17, 606105819);
		n = md5_ff(n, m, l, o, p[g + 3], 22, -1044525330);
		o = md5_ff(o, n, m, l, p[g + 4], 7, -176418897);
		l = md5_ff(l, o, n, m, p[g + 5], 12, 1200080426);
		m = md5_ff(m, l, o, n, p[g + 6], 17, -1473231341);
		n = md5_ff(n, m, l, o, p[g + 7], 22, -45705983);
		o = md5_ff(o, n, m, l, p[g + 8], 7, 1770035416);
		l = md5_ff(l, o, n, m, p[g + 9], 12, -1958414417);
		m = md5_ff(m, l, o, n, p[g + 10], 17, -42063);
		n = md5_ff(n, m, l, o, p[g + 11], 22, -1990404162);
		o = md5_ff(o, n, m, l, p[g + 12], 7, 1804603682);
		l = md5_ff(l, o, n, m, p[g + 13], 12, -40341101);
		m = md5_ff(m, l, o, n, p[g + 14], 17, -1502002290);
		n = md5_ff(n, m, l, o, p[g + 15], 22, 1236535329);
		o = md5_gg(o, n, m, l, p[g + 1], 5, -165796510);
		l = md5_gg(l, o, n, m, p[g + 6], 9, -1069501632);
		m = md5_gg(m, l, o, n, p[g + 11], 14, 643717713);
		n = md5_gg(n, m, l, o, p[g + 0], 20, -373897302);
		o = md5_gg(o, n, m, l, p[g + 5], 5, -701558691);
		l = md5_gg(l, o, n, m, p[g + 10], 9, 38016083);
		m = md5_gg(m, l, o, n, p[g + 15], 14, -660478335);
		n = md5_gg(n, m, l, o, p[g + 4], 20, -405537848);
		o = md5_gg(o, n, m, l, p[g + 9], 5, 568446438);
		l = md5_gg(l, o, n, m, p[g + 14], 9, -1019803690);
		m = md5_gg(m, l, o, n, p[g + 3], 14, -187363961);
		n = md5_gg(n, m, l, o, p[g + 8], 20, 1163531501);
		o = md5_gg(o, n, m, l, p[g + 13], 5, -1444681467);
		l = md5_gg(l, o, n, m, p[g + 2], 9, -51403784);
		m = md5_gg(m, l, o, n, p[g + 7], 14, 1735328473);
		n = md5_gg(n, m, l, o, p[g + 12], 20, -1926607734);
		o = md5_hh(o, n, m, l, p[g + 5], 4, -378558);
		l = md5_hh(l, o, n, m, p[g + 8], 11, -2022574463);
		m = md5_hh(m, l, o, n, p[g + 11], 16, 1839030562);
		n = md5_hh(n, m, l, o, p[g + 14], 23, -35309556);
		o = md5_hh(o, n, m, l, p[g + 1], 4, -1530992060);
		l = md5_hh(l, o, n, m, p[g + 4], 11, 1272893353);
		m = md5_hh(m, l, o, n, p[g + 7], 16, -155497632);
		n = md5_hh(n, m, l, o, p[g + 10], 23, -1094730640);
		o = md5_hh(o, n, m, l, p[g + 13], 4, 681279174);
		l = md5_hh(l, o, n, m, p[g + 0], 11, -358537222);
		m = md5_hh(m, l, o, n, p[g + 3], 16, -722521979);
		n = md5_hh(n, m, l, o, p[g + 6], 23, 76029189);
		o = md5_hh(o, n, m, l, p[g + 9], 4, -640364487);
		l = md5_hh(l, o, n, m, p[g + 12], 11, -421815835);
		m = md5_hh(m, l, o, n, p[g + 15], 16, 530742520);
		n = md5_hh(n, m, l, o, p[g + 2], 23, -995338651);
		o = md5_ii(o, n, m, l, p[g + 0], 6, -198630844);
		l = md5_ii(l, o, n, m, p[g + 7], 10, 1126891415);
		m = md5_ii(m, l, o, n, p[g + 14], 15, -1416354905);
		n = md5_ii(n, m, l, o, p[g + 5], 21, -57434055);
		o = md5_ii(o, n, m, l, p[g + 12], 6, 1700485571);
		l = md5_ii(l, o, n, m, p[g + 3], 10, -1894986606);
		m = md5_ii(m, l, o, n, p[g + 10], 15, -1051523);
		n = md5_ii(n, m, l, o, p[g + 1], 21, -2054922799);
		o = md5_ii(o, n, m, l, p[g + 8], 6, 1873313359);
		l = md5_ii(l, o, n, m, p[g + 15], 10, -30611744);
		m = md5_ii(m, l, o, n, p[g + 6], 15, -1560198380);
		n = md5_ii(n, m, l, o, p[g + 13], 21, 1309151649);
		o = md5_ii(o, n, m, l, p[g + 4], 6, -145523070);
		l = md5_ii(l, o, n, m, p[g + 11], 10, -1120210379);
		m = md5_ii(m, l, o, n, p[g + 2], 15, 718787259);
		n = md5_ii(n, m, l, o, p[g + 9], 21, -343485551);
		o = safe_add(o, j);
		n = safe_add(n, h);
		m = safe_add(m, f);
		l = safe_add(l, e)
	}
	return Array(o, n, m, l)
}
function md5_cmn(h, e, d, c, g, f) {
	return safe_add(bit_rol(safe_add(safe_add(e, h), safe_add(c, f)), g), d)
}
function md5_ff(g, f, k, j, e, i, h) {
	return md5_cmn((f & k) | ((~f) & j), g, f, e, i, h)
}
function md5_gg(g, f, k, j, e, i, h) {
	return md5_cmn((f & j) | (k & (~j)), g, f, e, i, h)
}
function md5_hh(g, f, k, j, e, i, h) {
	return md5_cmn(f ^ k ^ j, g, f, e, i, h)
}
function md5_ii(g, f, k, j, e, i, h) {
	return md5_cmn(k ^ (f | (~j)), g, f, e, i, h)
}
function safe_add(a, d) {
	var c = (a & 65535) + (d & 65535);
	var b = (a >> 16) + (d >> 16) + (c >> 16);
	return (b << 16) | (c & 65535)
}
function bit_rol(a, b) {
	return (a << b) | (a >>> (32 - b))
};

java版(代码来源：http://www.cnblogs.com/computer-lzy/archive/2011/04/28/2031649.html)：

package md5;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/*
 * MD5 加密算法
*/
public class MD5 {
    
    // 全局数组
    private final static String[] strDigits = { "0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };

    public MD5() {
    }

    // 返回形式为数字跟字符串
    private static String byteToArrayString(byte bByte) {
        int iRet = bByte;
        // System.out.println("iRet="+iRet);
        if (iRet < 0) {
            iRet += 256;
        }
        int iD1 = iRet / 16;
        int iD2 = iRet % 16;
        return strDigits[iD1] + strDigits[iD2];
    }

    // 返回形式只为数字
    private static String byteToNum(byte bByte) {
        int iRet = bByte;
        System.out.println("iRet1=" + iRet);
        if (iRet < 0) {
            iRet += 256;
        }
        return String.valueOf(iRet);
    }

    // 转换字节数组为16进制字串
    private static String byteToString(byte[] bByte) {
        StringBuffer sBuffer = new StringBuffer();
        for (int i = 0; i < bByte.length; i++) {
            sBuffer.append(byteToArrayString(bByte[i]));
        }
        return sBuffer.toString();
    }

    public static String GetMD5Code(String strObj) {
        String resultString = null;
        try {
            resultString = new String(strObj);
            MessageDigest md = MessageDigest.getInstance("MD5");
            // md.digest() 该函数返回值为存放哈希值结果的byte数组
            resultString = byteToString(md.digest(strObj.getBytes()));
        } catch (NoSuchAlgorithmException ex) {
            ex.printStackTrace();
        }
        return resultString;
    }

    public static void main(String[] args) {
        MD5 getMD5 = new MD5();
        System.out.println(getMD5.GetMD5Code(getMD5.GetMD5Code("aaaaaa")));
    }
}

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