ÿþfunction sha1Hash(msg)

{

    // constants [§4.2.1]

    var K = [0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6];





    // PREPROCESSING 

 

    msg += String.fromCharCode(0x80); // add trailing '1' bit to string [§5.1.1]



    // convert string msg into 512-bit/16-integer blocks arrays of ints [§5.2.1]

    var l = Math.ceil(msg.length/4) + 2;  // long enough to contain msg plus 2-word length

    var N = Math.ceil(l/16);              // in N 16-int blocks

    var M = new Array(N);

    for (var i=0; i<N; i++) {

        M[i] = new Array(16);

        for (var j=0; j<16; j++) {  // encode 4 chars per integer, big-endian encoding

            M[i][j] = (msg.charCodeAt(i*64+j*4)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16) | 

                      (msg.charCodeAt(i*64+j*4+2)<<8) | (msg.charCodeAt(i*64+j*4+3));

        }

    }

    // add length (in bits) into final pair of 32-bit integers (big-endian) [5.1.1]

    // note: most significant word would be ((len-1)*8 >>> 32, but since JS converts

    // bitwise-op args to 32 bits, we need to simulate this by arithmetic operators

    M[N-1][14] = ((msg.length-1)*8) / Math.pow(2, 32); M[N-1][14] = Math.floor(M[N-1][14])

    M[N-1][15] = ((msg.length-1)*8) & 0xffffffff;



    // set initial hash value [§5.3.1]

    var H0 = 0x67452301;

    var H1 = 0xefcdab89;

    var H2 = 0x98badcfe;

    var H3 = 0x10325476;

    var H4 = 0xc3d2e1f0;



    // HASH COMPUTATION [§6.1.2]



    var W = new Array(80); var a, b, c, d, e;

    for (var i=0; i<N; i++) {



        // 1 - prepare message schedule 'W'

        for (var t=0;  t<16; t++) W[t] = M[i][t];

        for (var t=16; t<80; t++) W[t] = ROTL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);



        // 2 - initialise five working variables a, b, c, d, e with previous hash value

        a = H0; b = H1; c = H2; d = H3; e = H4;



        // 3 - main loop

        for (var t=0; t<80; t++) {

            var s = Math.floor(t/20); // seq for blocks of 'f' functions and 'K' constants

            var T = (ROTL(a,5) + f(s,b,c,d) + e + K[s] + W[t]) & 0xffffffff;

            e = d;

            d = c;

            c = ROTL(b, 30);

            b = a;

            a = T;

        }



        // 4 - compute the new intermediate hash value

        H0 = (H0+a) & 0xffffffff;  // note 'addition modulo 2^32'

        H1 = (H1+b) & 0xffffffff; 

        H2 = (H2+c) & 0xffffffff; 

        H3 = (H3+d) & 0xffffffff; 

        H4 = (H4+e) & 0xffffffff;

    }



    return H0.toHexStr() + H1.toHexStr() + H2.toHexStr() + H3.toHexStr() + H4.toHexStr();

}



//

// function 'f' [§4.1.1]

//

function f(s, x, y, z) 

{

    switch (s) {

    case 0: return (x & y) ^ (~x & z);           // Ch()

    case 1: return x ^ y ^ z;                    // Parity()

    case 2: return (x & y) ^ (x & z) ^ (y & z);  // Maj()

    case 3: return x ^ y ^ z;                    // Parity()

    }

}



//

// rotate left (circular left shift) value x by n positions [§3.2.5]

//

function ROTL(x, n)

{

    return (x<<n) | (x>>>(32-n));

}



//

// extend Number class with a tailored hex-string method 

//   (note toString(16) is implementation-dependant, and 

//   in IE returns signed numbers when used on full words)

//

Number.prototype.toHexStr = function()

{

    var s="", v;

    for (var i=7; i>=0; i--) { v = (this>>>(i*4)) & 0xf; s += v.toString(16); }

    return s;

}