// SHA-256 hash function. Copyright-free.
// Requires typed arrays.
SHA256 = {};

SHA256.K = [
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 
    0x59f111f1, 0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 
    0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 
    0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 
    0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152, 
    0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 
    0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 
    0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 
    0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116, 0x1e376c08, 
    0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 
    0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 
    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2];

// The digest function returns the hash value (digest)
// as a 32 byte (typed) array.
// message: the string or byte array to hash
SHA256.digest = function(message) {
    var h0 = 0x6a09e667;
    var h1 = 0xbb67ae85;
    var h2 = 0x3c6ef372;
    var h3 = 0xa54ff53a;
    var h4 = 0x510e527f;
    var h5 = 0x9b05688c;
    var h6 = 0x1f83d9ab;
    var h7 = 0x5be0cd19;
    var K = SHA256.K;
    if (typeof message == 'string') {
       var s =  unescape(encodeURIComponent(message)); // UTF-8
        message = new Uint8Array(s.length);
        for (var i = 0; i < s.length; i++) {
            message[i] = s.charCodeAt(i) & 0xff;
        }
    }
    var length = message.length;
    var byteLength = Math.floor((length + 72) / 64) * 64;
    var wordLength = byteLength / 4;
    var bitLength = length * 8;
    var m = new Uint8Array(byteLength);
    m.set(message);
    m[length] = 0x80;
    m[byteLength - 4] = bitLength >>> 24;
    m[byteLength - 3] = (bitLength >>> 16) & 0xff;
    m[byteLength - 2] = (bitLength >>> 8) & 0xff;
    m[byteLength - 1] = bitLength & 0xff;
    var words = new Int32Array(wordLength);
    var byteIndex = 0;
    for (var i = 0; i < words.length; i++) {
        var word = m[byteIndex++] << 24;
        word |= m[byteIndex++] << 16;
        word |= m[byteIndex++] << 8;
        word |= m[byteIndex++];
        words[i] = word; 
    }
    var w = new Int32Array(64);
    for (var j = 0; j < wordLength; j += 16) {
        for (i = 0; i < 16; i++) {
            w[i] = words[j + i];
        }
        for (i = 16; i < 64; i++) {
            var v = w[i - 15];
            var s0 = (v >>> 7) | (v << 25);
            s0 ^= (v >>> 18) | (v << 14);
            s0 ^= (v >>> 3);
            v = w[i - 2];
            var s1 = (v >>> 17) | (v << 15);
            s1 ^= (v >>> 19) | (v << 13);
            s1 ^= (v >>> 10);
            w[i] = (w[i - 16] + s0 + w[i - 7] + s1) & 0xffffffff; 
        }
        var a = h0;
        var b = h1;
        var c = h2;
        var d = h3;
        var e = h4;
        var f = h5;
        var g = h6;
        var h = h7;
        for (i = 0; i < 64; i++) {
            s1 = (e >>> 6) | (e << 26);
            s1 ^= (e >>> 11) | (e << 21);
            s1 ^= (e >>> 25) | (e << 7);
            var ch = (e & f) ^ (~e & g);
            var temp1 = (h + s1 + ch + K[i] + w[i]) & 0xffffffff;
            s0 = (a >>> 2) | (a << 30);
            s0 ^= (a >>> 13) | (a << 19);
            s0 ^= (a >>> 22) | (a << 10);
            var maj = (a & b) ^ (a & c) ^ (b & c);
            var temp2 = (s0 + maj) & 0xffffffff;
            h = g
            g = f
            f = e
            e = (d + temp1) & 0xffffffff;
            d = c;
            c = b;
            b = a;
            a = (temp1 + temp2) & 0xffffffff;
        }
        h0 = (h0 + a) & 0xffffffff;
        h1 = (h1 + b) & 0xffffffff;
        h2 = (h2 + c) & 0xffffffff;
        h3 = (h3 + d) & 0xffffffff;
        h4 = (h4 + e) & 0xffffffff;
        h5 = (h5 + f) & 0xffffffff;
        h6 = (h6 + g) & 0xffffffff;
        h7 = (h7 + h) & 0xffffffff;
    }
    var hash = new Uint8Array(32);
    for (i = 0; i < 4; i++) {
        hash[i] = (h0 >>> (8 * (3 - i))) & 0xff;
        hash[i + 4] = (h1 >>> (8 * (3 - i))) & 0xff;
        hash[i + 8] = (h2 >>> (8 * (3 - i))) & 0xff;
        hash[i + 12] = (h3 >>> (8 * (3 - i))) & 0xff;
        hash[i + 16] = (h4 >>> (8 * (3 - i))) & 0xff;
        hash[i + 20] = (h5 >>> (8 * (3 - i))) & 0xff;
        hash[i + 24] = (h6 >>> (8 * (3 - i))) & 0xff;
        hash[i + 28] = (h7 >>> (8 * (3 - i))) & 0xff;
    }
    return hash;
}    

// The hash function returns the hash value as a hex string.
// message: the string or byte array to hash
SHA256.hash = function(message) {
    var digest = SHA256.digest(message);
    var hex = '';
	for (i = 0; i < digest.length; i++) {
		var s = '0' + digest[i].toString(16);
        hex += s.length > 2 ? s.substring(1) : s;
	}
    return hex;
}