function SHA1(msg, salt) {

    function rotate_left(n, s) {
        var t4 = (n << s) | (n >>> (32 - s));
        return t4;
    };

    function lsb_hex(val) {
        var str = "";
        var i;
        var vh;
        var vl;

        for (i = 0; i <= 6; i += 2) {
            vh = (val >>> (i * 4 + 4)) & 0x0f;
            vl = (val >>> (i * 4)) & 0x0f;
            str += vh.toString(16) + vl.toString(16);
        }
        return str;
    };

    function cvt_hex(val) {
        var str = "";
        var i;
        var v;

        for (i = 7; i >= 0; i--) {
            v = (val >>> (i * 4)) & 0x0f;
            str += v.toString(16);
        }
        return str;
    };


    function Utf8Encode(string) {
        string = string.replace(/\r\n/g, "\n");
        var utftext = "";

        for (var n = 0; n < string.length; n++) {

            var c = string.charCodeAt(n);

            if (c < 128) {
                utftext += String.fromCharCode(c);
            }
            else if ((c > 127) && (c < 2048)) {
                utftext += String.fromCharCode((c >> 6) | 192);
                utftext += String.fromCharCode((c & 63) | 128);
            }
            else {
                utftext += String.fromCharCode((c >> 12) | 224);
                utftext += String.fromCharCode(((c >> 6) & 63) | 128);
                utftext += String.fromCharCode((c & 63) | 128);
            }

        }

        return utftext;
    };

    function Utf16Encode(string) {
        var utftext = "";
        for (var n = 0; n < string.length; n++) {
            var c = string.charCodeAt(n);
            if (c < 0x1000) {
                utftext += String.fromCharCode(c);
                utftext += String.fromCharCode(0);
            }
            else {
                var cp = c - 0x1000;
                var w1 = 0xD800;
                var w2 = 0xDC00;
                w1 = (w1 & (cp >> 10));
                w2 = (w2 & (cp - (cp >> 10)));
                utftext += String.fromCharCode(w1);
                utftext += String.fromCharCode(w2);
            }
            
        }
       
        return utftext;
    }

    var blockstart;
    var i, j;
    var W = new Array(80);
    var H0 = 0x67452301;
    var H1 = 0xEFCDAB89;
    var H2 = 0x98BADCFE;
    var H3 = 0x10325476;
    var H4 = 0xC3D2E1F0;
    var A, B, C, D, E;
    var temp;

    //msg = Utf8Encode(msg);
    msg = Utf16Encode(msg);
    
    if (salt) {
        msg = salt + msg;
    }

    var msg_len = msg.length;

    var word_array = new Array();
    for (i = 0; i < msg_len - 3; i += 4) {
        j = msg.charCodeAt(i) << 24 | msg.charCodeAt(i + 1) << 16 |
		msg.charCodeAt(i + 2) << 8 | msg.charCodeAt(i + 3);
        word_array.push(j);
    }

    switch (msg_len % 4) {
        case 0:
            i = 0x080000000;
            break;
        case 1:
            i = msg.charCodeAt(msg_len - 1) << 24 | 0x0800000;
            break;

        case 2:
            i = msg.charCodeAt(msg_len - 2) << 24 | msg.charCodeAt(msg_len - 1) << 16 | 0x08000;
            break;

        case 3:
            i = msg.charCodeAt(msg_len - 3) << 24 | msg.charCodeAt(msg_len - 2) << 16 | msg.charCodeAt(msg_len - 1) << 8 | 0x80;
            break;
    }

    word_array.push(i);

    while ((word_array.length % 16) != 14) word_array.push(0);

    word_array.push(msg_len >>> 29);
    word_array.push((msg_len << 3) & 0x0ffffffff);


    for (blockstart = 0; blockstart < word_array.length; blockstart += 16) {

        for (i = 0; i < 16; i++) W[i] = word_array[blockstart + i];
        for (i = 16; i <= 79; i++) W[i] = rotate_left(W[i - 3] ^ W[i - 8] ^ W[i - 14] ^ W[i - 16], 1);

        A = H0;
        B = H1;
        C = H2;
        D = H3;
        E = H4;

        for (i = 0; i <= 19; i++) {
            temp = (rotate_left(A, 5) + ((B & C) | (~B & D)) + E + W[i] + 0x5A827999) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B, 30);
            B = A;
            A = temp;
        }

        for (i = 20; i <= 39; i++) {
            temp = (rotate_left(A, 5) + (B ^ C ^ D) + E + W[i] + 0x6ED9EBA1) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B, 30);
            B = A;
            A = temp;
        }

        for (i = 40; i <= 59; i++) {
            temp = (rotate_left(A, 5) + ((B & C) | (B & D) | (C & D)) + E + W[i] + 0x8F1BBCDC) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B, 30);
            B = A;
            A = temp;
        }

        for (i = 60; i <= 79; i++) {
            temp = (rotate_left(A, 5) + (B ^ C ^ D) + E + W[i] + 0xCA62C1D6) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B, 30);
            B = A;
            A = temp;
        }

        H0 = (H0 + A) & 0x0ffffffff;
        H1 = (H1 + B) & 0x0ffffffff;
        H2 = (H2 + C) & 0x0ffffffff;
        H3 = (H3 + D) & 0x0ffffffff;
        H4 = (H4 + E) & 0x0ffffffff;

    }

    var temp = cvt_hex(H0) + cvt_hex(H1) + cvt_hex(H2) + cvt_hex(H3) + cvt_hex(H4);

    return temp.toLowerCase();
}