// The SHA-1 code in this section was copied from:
      // A JavaScript implementation of the Secure Hash Algorithm, SHA-1, as defined in FIPS PUB 180-1
      // Version 2.1a Copyright Paul Johnston 2000 - 2002.
      // Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
      // Distributed under the BSD License
      // See http://pajhome.org.uk/crypt/md5 for details.

      function b64_sha1(s){return binb2b64(core_sha1(str2binb(s),s.length * 8));}
      function b64_hmac_sha1(key, data){ return binb2b64(core_hmac_sha1(key, data));}

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

      function core_sha1(x, len)
      {
      x[len >> 5] |= 0x80 << (24 - len % 32);  // append padding
  x[((len + 64 >> 9) << 4) + 15] = len;

  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)
  {
    var olda = a;
    var oldb = b;
    var oldc = c;
    var oldd = d;
    var olde = e;

    for (var j = 0; j < 80; j++)
    {
      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 Array(a, b, c, d, e);
}

// Perform the appropriate triplet combination function for the current iteration

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;
}

// Determine the appropriate additive constant for the current iteration

function sha1_kt(t)
{
  return (t < 20) ? 1518500249
                  : (t < 40) ? 1859775393
                             : (t < 60) ? -1894007588
                                        : -899497514;
}

// Calculate the HMAC-SHA1 of a key and some data

function core_hmac_sha1(key, data)
{
  var bkey = str2binb(key);
  if (bkey.length > 16)
  {
    bkey = core_sha1(bkey, key.length * 8);
  }

  var ipad = Array(16), opad = Array(16);
  for (var i = 0; i < 16; i++)
  {
    ipad[i] = bkey[i] ^ 0x36363636;
    opad[i] = bkey[i] ^ 0x5C5C5C5C;
  }

  var hash = core_sha1(ipad.concat(str2binb(data)), 512 + data.length * 8);
  return core_sha1(opad.concat(hash), 512 + 160);
}

// Add integers, wrapping at 2^32. This uses 16-bit operations internally
// to work around bugs in some JS interpreters.

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.

function rol(num, cnt)
{
  return (num << cnt) | (num >>> (32 - cnt));
}


// Convert an 8-bit string to an array of big-endian words
// Characters > 255 have their hi-byte silently ignored.

function str2binb(str)
{
  var bin = Array();
  var mask = (1 << 8) - 1;
  for (var i = 0; i < str.length * 8; i += 8)
  {
    bin[i>>5] |= (str.charCodeAt(i / 8) & mask) << (32 - 8 - i%32);
  }
  
  return bin;
}

// Convert an array of big-endian words to a string

function binb2str(bin)
{
  var str = "";
  var mask = (1 << 8) - 1;
  for (var i = 0; i < bin.length * 32; i += 8)
  {
    str += String.fromCharCode((bin[i>>5] >>> (32 - 8 - i%32)) & mask);
  }
  
  return str;
}

// Convert an array of big-endian words to a base-64 string

function binb2b64(binarray)
{
  var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  var str = "";
  for (var i = 0; i < binarray.length * 4; i += 3)
  {
    var triplet = (((binarray[i   >> 2] >> 8 * (3 -  i   %4)) & 0xFF) << 16)
                  | (((binarray[i+1 >> 2] >> 8 * (3 - (i+1)%4)) & 0xFF) << 8 )
                  |  ((binarray[i+2 >> 2] >> 8 * (3 - (i+2)%4)) & 0xFF);
    
    for (var j = 0; j < 4; j++)
    {
      if (i * 8 + j * 6 > binarray.length * 32)
      {
        str += '=';
      }
      else
      {
        str += tab.charAt((triplet >> 6*(3-j)) & 0x3F);
      }
    }
  }
  
  return str;
}

function hashExample()
{
  document.getElementById('hashExampleResult').innerHTML = '<strong>' + b64_sha1(document.getElementById('hashExample').value) + '<strong>';
          }

          function hmacExample()
          {
          document.getElementById('hmacExampleResult').innerHTML = '<strong>' + b64_hmac_sha1(document.getElementById('hmacKeyExample').value, document.getElementById('hmacTextExample').value) + '<strong>';
}