function md5cycle(x, k) {
  var a = x[0], b = x[1], c = x[2], d = x[3]

  a = ff(a, b, c, d, k[0], 7, -680876936)
  d = ff(d, a, b, c, k[1], 12, -389564586)
  c = ff(c, d, a, b, k[2], 17, 606105819)
  b = ff(b, c, d, a, k[3], 22, -1044525330)
  a = ff(a, b, c, d, k[4], 7, -176418897)
  d = ff(d, a, b, c, k[5], 12, 1200080426)
  c = ff(c, d, a, b, k[6], 17, -1473231341)
  b = ff(b, c, d, a, k[7], 22, -45705983)
  a = ff(a, b, c, d, k[8], 7, 1770035416)
  d = ff(d, a, b, c, k[9], 12, -1958414417)
  c = ff(c, d, a, b, k[10], 17, -42063)
  b = ff(b, c, d, a, k[11], 22, -1990404162)
  a = ff(a, b, c, d, k[12], 7, 1804603682)
  d = ff(d, a, b, c, k[13], 12, -40341101)
  c = ff(c, d, a, b, k[14], 17, -1502002290)
  b = ff(b, c, d, a, k[15], 22, 1236535329)

  a = gg(a, b, c, d, k[1], 5, -165796510)
  d = gg(d, a, b, c, k[6], 9, -1069501632)
  c = gg(c, d, a, b, k[11], 14, 643717713)
  b = gg(b, c, d, a, k[0], 20, -373897302)
  a = gg(a, b, c, d, k[5], 5, -701558691)
  d = gg(d, a, b, c, k[10], 9, 38016083)
  c = gg(c, d, a, b, k[15], 14, -660478335)
  b = gg(b, c, d, a, k[4], 20, -405537848)
  a = gg(a, b, c, d, k[9], 5, 568446438)
  d = gg(d, a, b, c, k[14], 9, -1019803690)
  c = gg(c, d, a, b, k[3], 14, -187363961)
  b = gg(b, c, d, a, k[8], 20, 1163531501)
  a = gg(a, b, c, d, k[13], 5, -1444681467)
  d = gg(d, a, b, c, k[2], 9, -51403784)
  c = gg(c, d, a, b, k[7], 14, 1735328473)
  b = gg(b, c, d, a, k[12], 20, -1926607734)

  a = hh(a, b, c, d, k[5], 4, -378558)
  d = hh(d, a, b, c, k[8], 11, -2022574463)
  c = hh(c, d, a, b, k[11], 16, 1839030562)
  b = hh(b, c, d, a, k[14], 23, -35309556)
  a = hh(a, b, c, d, k[1], 4, -1530992060)
  d = hh(d, a, b, c, k[4], 11, 1272893353)
  c = hh(c, d, a, b, k[7], 16, -155497632)
  b = hh(b, c, d, a, k[10], 23, -1094730640)
  a = hh(a, b, c, d, k[13], 4, 681279174)
  d = hh(d, a, b, c, k[0], 11, -358537222)
  c = hh(c, d, a, b, k[3], 16, -722521979)
  b = hh(b, c, d, a, k[6], 23, 76029189)
  a = hh(a, b, c, d, k[9], 4, -640364487)
  d = hh(d, a, b, c, k[12], 11, -421815835)
  c = hh(c, d, a, b, k[15], 16, 530742520)
  b = hh(b, c, d, a, k[2], 23, -995338651)

  a = ii(a, b, c, d, k[0], 6, -198630844)
  d = ii(d, a, b, c, k[7], 10, 1126891415)
  c = ii(c, d, a, b, k[14], 15, -1416354905)
  b = ii(b, c, d, a, k[5], 21, -57434055)
  a = ii(a, b, c, d, k[12], 6, 1700485571)
  d = ii(d, a, b, c, k[3], 10, -1894986606)
  c = ii(c, d, a, b, k[10], 15, -1051523)
  b = ii(b, c, d, a, k[1], 21, -2054922799)
  a = ii(a, b, c, d, k[8], 6, 1873313359)
  d = ii(d, a, b, c, k[15], 10, -30611744)
  c = ii(c, d, a, b, k[6], 15, -1560198380)
  b = ii(b, c, d, a, k[13], 21, 1309151649)
  a = ii(a, b, c, d, k[4], 6, -145523070)
  d = ii(d, a, b, c, k[11], 10, -1120210379)
  c = ii(c, d, a, b, k[2], 15, 718787259)
  b = ii(b, c, d, a, k[9], 21, -343485551)

  x[0] = add32(a, x[0])
  x[1] = add32(b, x[1])
  x[2] = add32(c, x[2])
  x[3] = add32(d, x[3])
}

function cmn(q, a, b, x, s, t) {
  a = add32(add32(a, q), add32(x, t))
  return add32((a << s) | (a >>> (32 - s)), b)
}

function ff(a, b, c, d, x, s, t) {
  return cmn((b & c) | ((~b) & d), a, b, x, s, t)
}

function gg(a, b, c, d, x, s, t) {
  return cmn((b & d) | (c & (~d)), a, b, x, s, t)
}

function hh(a, b, c, d, x, s, t) {
  return cmn(b ^ c ^ d, a, b, x, s, t)
}

function ii(a, b, c, d, x, s, t) {
  return cmn(c ^ (b | (~d)), a, b, x, s, t)
}

function md51(s) {
  txt = ""
  var n = s.length,
    state = [1732584193, -271733879, -1732584194, 271733878], i
  for (i = 64; i <= s.length; i += 64) {
    md5cycle(state, md5blk(s.substring(i - 64, i)))
  }
  s = s.substring(i - 64)
  var tail = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  for (i = 0; i < s.length; i++)
    tail[i >> 2] |= s.charCodeAt(i) << ((i % 4) << 3)
  tail[i >> 2] |= 0x80 << ((i % 4) << 3)
  if (i > 55) {
    md5cycle(state, tail)
    for (i = 0; i < 16; i++) tail[i] = 0
  }
  tail[14] = n * 8
  md5cycle(state, tail)
  return state
}

/* there needs to be support for Unicode here,
 * unless we pretend that we can redefine the MD-5
 * algorithm for multi-byte characters (perhaps
 * by adding every four 16-bit characters and
 * shortening the sum to 32 bits). Otherwise
 * I suggest performing MD-5 as if every character
 * was two bytes--e.g., 0040 0025 = @%--but then
 * how will an ordinary MD-5 sum be matched?
 * There is no way to standardize text to something
 * like UTF-8 before transformation; speed cost is
 * utterly prohibitive. The JavaScript standard
 * itself needs to look at this: it should start
 * providing access to strings as preformed UTF-8
 * 8-bit unsigned value arrays.
 */
function md5blk(s) { /* I figured global was faster.   */
  var md5blks = [], i /* Andy King said do it this way. */
  for (i = 0; i < 64; i += 4) {
    md5blks[i >> 2] = s.charCodeAt(i)
    + (s.charCodeAt(i + 1) << 8)
    + (s.charCodeAt(i + 2) << 16)
    + (s.charCodeAt(i + 3) << 24)
  }
  return md5blks
}

var hex_chr = "0123456789abcdef".split("")

function rhex(n) {
  var s = "", j = 0
  for (; j < 4; j++)
    s += hex_chr[(n >> (j * 8 + 4)) & 0x0F]
    + hex_chr[(n >> (j * 8)) & 0x0F]
  return s
}

function hex(x) {
  for (var i = 0; i < x.length; i++)
    x[i] = rhex(x[i])
  return x.join("")
}

function md5(s) {
  return hex(md51(s))
}

/* this function is much faster,
so if possible we use it. Some IEs
are the only ones I know of that
need the idiotic second function,
generated by an if clause.  */

function add32(a, b) {
  return (a + b) & 0xFFFFFFFF
}

if (md5("hello") != "5d41402abc4b2a76b9719d911017c592") {
  function add32(x, y) {
    var lsw = (x & 0xFFFF) + (y & 0xFFFF),
      msw = (x >> 16) + (y >> 16) + (lsw >> 16)
    return (msw << 16) | (lsw & 0xFFFF)
  }
}