A JavaScript implementation of the Secure Hash Algorithm, SHA-1, as defined in FIPS PUB 180-1.

/*
 * A JavaScript implementation of the Secure Hash Algorithm, SHA-1, as defined
 * in FIPS PUB 180-1
 * Version 2.1 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.
 */

/*
 * Configurable variables. You may need to tweak these to be compatible with
 * the server-side, but the defaults work in most cases.
 */
var hexcase = 0; /* hex output format. 0 - lowercase; 1 - uppercase        */
var b64pad = ""; /* base-64 pad character. "=" for strict RFC compliance   */
var chrsz = 8; /* bits per input character. 8 - ASCII; 16 - Unicode      */

/*
 * These are the functions you'll usually want to call
 * They take string arguments and return either hex or base-64 encoded strings
 */
function hex_sha1(s) {
  return binb2hex(core_sha1(str2binb(s), s.length * chrsz));
}

function b64_sha1(s) {
  return binb2b64(core_sha1(str2binb(s), s.length * chrsz));
}

function str_sha1(s) {
  return binb2str(core_sha1(str2binb(s), s.length * chrsz));
}

function hex_hmac_sha1(key, data) {
  return binb2hex(core_hmac_sha1(key, data));
}

function b64_hmac_sha1(key, data) {
  return binb2b64(core_hmac_sha1(key, data));
}

function str_hmac_sha1(key, data) {
  return binb2str(core_hmac_sha1(key, data));
}

/*
 * Perform a simple self-test to see if the VM is working
 */
function sha1_vm_test() {
  return hex_sha1("abc") == "a9993e364706816aba3e25717850c26c9cd0d89d";
}

/*
 * Calculate the SHA-1 of an array of big-endian words, and a bit length
 */
function core_sha1(x, len) { /* append padding */
  x[len >> 5] |= 0x80 << (24 - len % 32);
  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 * chrsz);

  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 * chrsz);
  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 or 16-bit string to an array of big-endian words
 * In 8-bit function, characters >255 have their hi-byte silently ignored.
 */
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;
}

/*
 * Convert an array of big-endian words to a string
 */
function binb2str(bin) {
  var str = "";
  var mask = (1 << chrsz) - 1;
  for (var i = 0; i < bin.length * 32; i += chrsz)
  str += String.fromCharCode((bin[i >> 5] >>> (24 - i % 32)) & mask);
  return str;
}

/*
 * Convert an array of big-endian words to a hex string.
 */
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;
}

/*
 * 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 += b64pad;
      else str += tab.charAt((triplet >> 6 * (3 - j)) & 0x3F);
    }
  }
  return str;
}