本文实例讲述了JavaScript实现SHA-1加密算法的方法--------调用方法：hex_sha1即可

/*

 *

 * A JavaScript implementation of the Secure Hash Algorithm, SHA-1, as defined

 * in FIPS PUB 180-1

 *

 * By lizq

 *

 * 2006-11-11

 *

 */

/*

 *

 * Configurable variables.

 *

 */

var hexcase = 0; /* hex output format. 0 - lowercase; 1 - uppercase */

var chrsz = 8; /* bits per input character. 8 - ASCII; 16 - Unicode */

/*

 *

 * The main function to calculate message digest

 *

 */

function hex_sha1(s){

    return binb2hex(core_sha1(AlignSHA1(s)));

}

/*

 *

 * Perform a simple self-test to see if the VM is working

 *

 */

function sha1_vm_test(){

    return hex_sha1("abc") == "a9993e364706816aba3e25717850c26c9cd0d89d";

}

/*

 *

 * Calculate the SHA-1 of an array of big-endian words, and a bit length

 *

 */

function core_sha1(blockArray){

    var x = blockArray; // append padding

    var w = Array(80);

    var a = 1732584193;

    var b = -271733879;

    var c = -1732584194;

    var d = 271733878;

    var e = -1009589776;

    for (var i = 0; i < x.length; i += 16) // 每次处理512位 16*32

    {

        var olda = a;

        var oldb = b;

        var oldc = c;

        var oldd = d;

        var olde = e;

        for (var j = 0; j < 80; j++) // 对每个512位进行80步操作

        {

            if (j < 16) 

                w[j] = x[i + j];

            else

                w[j] = rol(w[j - 3] ^ w[j - 8] ^ w[j - 14] ^ w[j - 16], 1);

            var t = safe_add(safe_add(rol(a, 5), sha1_ft(j, b, c, d)), safe_add(safe_add(e, w[j]), sha1_kt(j)));

            e = d;

            d = c;

            c = rol(b, 30);

            b = a;

            a = t;

        }

        a = safe_add(a, olda);

        b = safe_add(b, oldb);

        c = safe_add(c, oldc);

        d = safe_add(d, oldd);

        e = safe_add(e, olde);

    }

    return new Array(a, b, c, d, e);

}

/*

 *

 * Perform the appropriate triplet combination function for the current

 * iteration

 *

 * 返回对应F函数的值

 *

 */

function sha1_ft(t, b, c, d){

    if (t < 20) 

        return (b & c) | ((~ b) & d);

    if (t < 40) 

        return b ^ c ^ d;

    if (t < 60) 

        return (b & c) | (b & d) | (c & d);

    return b ^ c ^ d; // t<80

}

/*

 *

 * Determine the appropriate additive constant for the current iteration

 *

 * 返回对应的Kt值

 *

 */

function sha1_kt(t){

    return (t < 20) ? 1518500249 : (t < 40) ? 1859775393 : (t < 60) ? -1894007588 : -899497514;

}

/*

 *

 * Add integers, wrapping at 2^32. This uses 16-bit operations internally

 *

 * to work around bugs in some JS interpreters.

 *

 * 将32位数拆成高16位和低16位分别进行相加，从而实现 MOD 2^32 的加法

 *

 */

function safe_add(x, y){

    var lsw = (x & 0xFFFF) + (y & 0xFFFF);

    var msw = (x >> 16) + (y >> 16) + (lsw >> 16);

    return (msw << 16) | (lsw & 0xFFFF);

}

/*

 *

 * Bitwise rotate a 32-bit number to the left.

 *

 * 32位二进制数循环左移

 *

 */

function rol(num, cnt){

    return (num << cnt) | (num >>> (32 - cnt));

}

/*

 *

 * The standard SHA1 needs the input string to fit into a block

 *

 * This function align the input string to meet the requirement

 *

 */

function AlignSHA1(str){

    var nblk = ((str.length + 8) >> 6) + 1, blks = new Array(nblk * 16);

    for (var i = 0; i < nblk * 16; i++) 

        blks[i] = 0;

    for (i = 0; i < str.length; i++) 

        blks[i >> 2] |= str.charCodeAt(i) << (24 - (i & 3) * 8);

    blks[i >> 2] |= 0x80 << (24 - (i & 3) * 8);

    blks[nblk * 16 - 1] = str.length * 8;

    return blks;

}

/*

 *

 * Convert an array of big-endian words to a hex string.

 *

 */

function binb2hex(binarray){

    var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";

    var str = "";

    for (var i = 0; i < binarray.length * 4; i++) {

        str += hex_tab.charAt((binarray[i >> 2] >> ((3 - i % 4) * 8 + 4)) & 0xF) +

        hex_tab.charAt((binarray[i >> 2] >> ((3 - i % 4) * 8)) & 0xF);

    }

    return str;

}

/*

 *

 * calculate MessageDigest accord to source message that inputted

 *

 */

function calcDigest(){

    var digestM = hex_sha1(document.SHAForm.SourceMessage.value);

    document.SHAForm.MessageDigest.value = digestM;

}