function SHA256(s) {
    var chrsz = 8;
    var hexcase = 0;


    function safe_add(x, y) {

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

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

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

    }


    function S(X, n) { return (X >>> n) | (X << (32 - n)); }

    function R(X, n) { return (X >>> n); }

    function Ch(x, y, z) { return ((x & y) ^ ((~x) & z)); }

    function Maj(x, y, z) { return ((x & y) ^ (x & z) ^ (y & z)); }

    function Sigma0256(x) { return (S(x, 2) ^ S(x, 13) ^ S(x, 22)); }

    function Sigma1256(x) { return (S(x, 6) ^ S(x, 11) ^ S(x, 25)); }

    function Gamma0256(x) { return (S(x, 7) ^ S(x, 18) ^ R(x, 3)); }

    function Gamma1256(x) { return (S(x, 17) ^ S(x, 19) ^ R(x, 10)); }


    function core_sha256(m, l) {

        var K = new Array(0x428A2F98, 0x71374491, 0xB5C0FBCF, 0xE9B5DBA5, 0x3956C25B, 0x59F111F1, 0x923F82A4, 0xAB1C5ED5, 0xD807AA98, 0x12835B01, 0x243185BE, 0x550C7DC3, 0x72BE5D74, 0x80DEB1FE, 0x9BDC06A7, 0xC19BF174, 0xE49B69C1, 0xEFBE4786, 0xFC19DC6, 0x240CA1CC, 0x2DE92C6F, 0x4A7484AA, 0x5CB0A9DC, 0x76F988DA, 0x983E5152, 0xA831C66D, 0xB00327C8, 0xBF597FC7, 0xC6E00BF3, 0xD5A79147, 0x6CA6351, 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);

        var HASH = new Array(0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A, 0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19);

        var W = new Array(64);

        var a, b, c, d, e, f, g, h, i, j;

        var T1, T2;


        m[l >> 5] |= 0x80 << (24 - l % 32);

        m[((l + 64 >> 9) << 4) + 15] = l;


        for (var i = 0; i < m.length; i += 16) {

            a = HASH[0];

            b = HASH[1];

            c = HASH[2];

            d = HASH[3];

            e = HASH[4];

            f = HASH[5];

            g = HASH[6];

            h = HASH[7];


            for (var j = 0; j < 64; j++) {

                if (j < 16) W[j] = m[j + i];

                else W[j] = safe_add(safe_add(safe_add(Gamma1256(W[j - 2]), W[j - 7]), Gamma0256(W[j - 15])), W[j - 16]);


                T1 = safe_add(safe_add(safe_add(safe_add(h, Sigma1256(e)), Ch(e, f, g)), K[j]), W[j]);

                T2 = safe_add(Sigma0256(a), Maj(a, b, c));


                h = g;

                g = f;

                f = e;

                e = safe_add(d, T1);

                d = c;

                c = b;

                b = a;

                a = safe_add(T1, T2);

            }


            HASH[0] = safe_add(a, HASH[0]);

            HASH[1] = safe_add(b, HASH[1]);

            HASH[2] = safe_add(c, HASH[2]);

            HASH[3] = safe_add(d, HASH[3]);

            HASH[4] = safe_add(e, HASH[4]);

            HASH[5] = safe_add(f, HASH[5]);

            HASH[6] = safe_add(g, HASH[6]);

            HASH[7] = safe_add(h, HASH[7]);

        }

        return HASH;

    }


    function str2binb(str) {

        var bin = Array();

        var mask = (1 << chrsz) - 1;

        for (var i = 0; i < str.length * chrsz; i += chrsz) {

            bin[i >> 5] |= (str.charCodeAt(i / chrsz) & mask) << (24 - i % 32);

        }

        return bin;

    }


    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 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;

    }


    s = Utf8Encode(s);

    return binb2hex(core_sha256(str2binb(s), s.length * chrsz));

}