JavaScript SHA512&SHA256加密算法详解

JavaScript SHA512加密算法详细代码

/*
 * A JavaScript implementation of the Secure Hash Algorithm, SHA-512, as defined
 * in FIPS 180-2
 * Version 2.2 Copyright Anonymous Contributor, Paul Johnston 2000 - 2009.
 * 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  */

/*
 * 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_sha512(s)  { return rstr2hex(rstr_sha512(str2rstr_utf8(s))); }
function b64_sha512(s)  { return rstr2b64(rstr_sha512(str2rstr_utf8(s))); }
function any_sha512(s, e) { return rstr2any(rstr_sha512(str2rstr_utf8(s)), e);}
function hex_hmac_sha512(k, d)
 { return rstr2hex(rstr_hmac_sha512(str2rstr_utf8(k), str2rstr_utf8(d))); }
function b64_hmac_sha512(k, d)
 { return rstr2b64(rstr_hmac_sha512(str2rstr_utf8(k), str2rstr_utf8(d))); }
function any_hmac_sha512(k, d, e)
 { return rstr2any(rstr_hmac_sha512(str2rstr_utf8(k), str2rstr_utf8(d)), e);}

/*
 * Perform a simple self-test to see if the VM is working
 */
function sha512_vm_test()
{
 return hex_sha512("abc").toLowerCase() ==
  "ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a" +
  "2192992a274fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f";
}

/*
 * Calculate the SHA-512 of a raw string
 */
function rstr_sha512(s)
{
 return binb2rstr(binb_sha512(rstr2binb(s), s.length * 8));
}

/*
 * Calculate the HMAC-SHA-512 of a key and some data (raw strings)
 */
function rstr_hmac_sha512(key, data)
{
 var bkey = rstr2binb(key);
 if(bkey.length > 32) bkey = binb_sha512(bkey, key.length * 8);

 var ipad = Array(32), opad = Array(32);
 for(var i = 0; i < 32; i++)
 {
  ipad[i] = bkey[i] ^ 0x36363636;
  opad[i] = bkey[i] ^ 0x5C5C5C5C;
 }

 var hash = binb_sha512(ipad.concat(rstr2binb(data)), 1024 + data.length * 8);
 return binb2rstr(binb_sha512(opad.concat(hash), 1024 + 512));
}

/*
 * Convert a raw string to a hex string
 */
function rstr2hex(input)
{
 try { hexcase } catch(e) { hexcase=0; }
 var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
 var output = "";
 var x;
 for(var i = 0; i < input.length; i++)
 {
  x = input.charCodeAt(i);
  output += hex_tab.charAt((x >>> 4) & 0x0F)
      + hex_tab.charAt( x    & 0x0F);
 }
 return output;
}

/*
 * Convert a raw string to a base-64 string
 */
function rstr2b64(input)
{
 try { b64pad } catch(e) { b64pad=''; }
 var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 var output = "";
 var len = input.length;
 for(var i = 0; i < len; i += 3)
 {
  var triplet = (input.charCodeAt(i) << 16)
        | (i + 1 < len ? input.charCodeAt(i+1) << 8 : 0)
        | (i + 2 < len ? input.charCodeAt(i+2)   : 0);
  for(var j = 0; j < 4; j++)
  {
   if(i * 8 + j * 6 > input.length * 8) output += b64pad;
   else output += tab.charAt((triplet >>> 6*(3-j)) & 0x3F);
  }
 }
 return output;
}

/*
 * Convert a raw string to an arbitrary string encoding
 */
function rstr2any(input, encoding)
{
 var divisor = encoding.length;
 var i, j, q, x, quotient;

 /* Convert to an array of 16-bit big-endian values, forming the dividend */
 var dividend = Array(Math.ceil(input.length / 2));
 for(i = 0; i < dividend.length; i++)
 {
  dividend[i] = (input.charCodeAt(i * 2) << 8) | input.charCodeAt(i * 2 + 1);
 }

 /*
  * Repeatedly perform a long division. The binary array forms the dividend,
  * the length of the encoding is the divisor. Once computed, the quotient
  * forms the dividend for the next step. All remainders are stored for later
  * use.
  */
 var full_length = Math.ceil(input.length * 8 /
                  (Math.log(encoding.length) / Math.log(2)));
 var remainders = Array(full_length);
 for(j = 0; j < full_length; j++)
 {
  quotient = Array();
  x = 0;
  for(i = 0; i < dividend.length; i++)
  {
   x = (x << 16) + dividend[i];
   q = Math.floor(x / divisor);
   x -= q * divisor;
   if(quotient.length > 0 || q > 0)
    quotient[quotient.length] = q;
  }
  remainders[j] = x;
  dividend = quotient;
 }

 /* Convert the remainders to the output string */
 var output = "";
 for(i = remainders.length - 1; i >= 0; i--)
  output += encoding.charAt(remainders[i]);

 return output;
}

/*
 * Encode a string as utf-8.
 * For efficiency, this assumes the input is valid utf-16.
 */
function str2rstr_utf8(input)
{
 var output = "";
 var i = -1;
 var x, y;

 while(++i < input.length)
 {
  /* Decode utf-16 surrogate pairs */
  x = input.charCodeAt(i);
  y = i + 1 < input.length ? input.charCodeAt(i + 1) : 0;
  if(0xD800 <= x && x <= 0xDBFF && 0xDC00 <= y && y <= 0xDFFF)
  {
   x = 0x10000 + ((x & 0x03FF) << 10) + (y & 0x03FF);
   i++;
  }

  /* Encode output as utf-8 */
  if(x <= 0x7F)
   output += String.fromCharCode(x);
  else if(x <= 0x7FF)
   output += String.fromCharCode(0xC0 | ((x >>> 6 ) & 0x1F),
                  0x80 | ( x     & 0x3F));
  else if(x <= 0xFFFF)
   output += String.fromCharCode(0xE0 | ((x >>> 12) & 0x0F),
                  0x80 | ((x >>> 6 ) & 0x3F),
                  0x80 | ( x     & 0x3F));
  else if(x <= 0x1FFFFF)
   output += String.fromCharCode(0xF0 | ((x >>> 18) & 0x07),
                  0x80 | ((x >>> 12) & 0x3F),
                  0x80 | ((x >>> 6 ) & 0x3F),
                  0x80 | ( x     & 0x3F));
 }
 return output;
}

/*
 * Encode a string as utf-16
 */
function str2rstr_utf16le(input)
{
 var output = "";
 for(var i = 0; i < input.length; i++)
  output += String.fromCharCode( input.charCodeAt(i)    & 0xFF,
                 (input.charCodeAt(i) >>> 8) & 0xFF);
 return output;
}

function str2rstr_utf16be(input)
{
 var output = "";
 for(var i = 0; i < input.length; i++)
  output += String.fromCharCode((input.charCodeAt(i) >>> 8) & 0xFF,
                  input.charCodeAt(i)    & 0xFF);
 return output;
}

/*
 * Convert a raw string to an array of big-endian words
 * Characters >255 have their high-byte silently ignored.
 */
function rstr2binb(input)
{
 var output = Array(input.length >> 2);
 for(var i = 0; i < output.length; i++)
  output[i] = 0;
 for(var i = 0; i < input.length * 8; i += 8)
  output[i>>5] |= (input.charCodeAt(i / 8) & 0xFF) << (24 - i % 32);
 return output;
}

/*
 * Convert an array of big-endian words to a string
 */
function binb2rstr(input)
{
 var output = "";
 for(var i = 0; i < input.length * 32; i += 8)
  output += String.fromCharCode((input[i>>5] >>> (24 - i % 32)) & 0xFF);
 return output;
}

/*
 * Calculate the SHA-512 of an array of big-endian dwords, and a bit length
 */
var sha512_k;
function binb_sha512(x, len)
{
 if(sha512_k == undefined)
 {
  //SHA512 constants
  sha512_k = new Array(
new int64(0x428a2f98, -685199838), new int64(0x71374491, 0x23ef65cd),
new int64(-1245643825, -330482897), new int64(-373957723, -2121671748),
new int64(0x3956c25b, -213338824), new int64(0x59f111f1, -1241133031),
new int64(-1841331548, -1357295717), new int64(-1424204075, -630357736),
new int64(-670586216, -1560083902), new int64(0x12835b01, 0x45706fbe),
new int64(0x243185be, 0x4ee4b28c), new int64(0x550c7dc3, -704662302),
new int64(0x72be5d74, -226784913), new int64(-2132889090, 0x3b1696b1),
new int64(-1680079193, 0x25c71235), new int64(-1046744716, -815192428),
new int64(-459576895, -1628353838), new int64(-272742522, 0x384f25e3),
new int64(0xfc19dc6, -1953704523), new int64(0x240ca1cc, 0x77ac9c65),
new int64(0x2de92c6f, 0x592b0275), new int64(0x4a7484aa, 0x6ea6e483),
new int64(0x5cb0a9dc, -1119749164), new int64(0x76f988da, -2096016459),
new int64(-1740746414, -295247957), new int64(-1473132947, 0x2db43210),
new int64(-1341970488, -1728372417), new int64(-1084653625, -1091629340),
new int64(-958395405, 0x3da88fc2), new int64(-710438585, -1828018395),
new int64(0x6ca6351, -536640913), new int64(0x14292967, 0xa0e6e70),
new int64(0x27b70a85, 0x46d22ffc), new int64(0x2e1b2138, 0x5c26c926),
new int64(0x4d2c6dfc, 0x5ac42aed), new int64(0x53380d13, -1651133473),
new int64(0x650a7354, -1951439906), new int64(0x766a0abb, 0x3c77b2a8),
new int64(-2117940946, 0x47edaee6), new int64(-1838011259, 0x1482353b),
new int64(-1564481375, 0x4cf10364), new int64(-1474664885, -1136513023),
new int64(-1035236496, -789014639), new int64(-949202525, 0x654be30),
new int64(-778901479, -688958952), new int64(-694614492, 0x5565a910),
new int64(-200395387, 0x5771202a), new int64(0x106aa070, 0x32bbd1b8),
new int64(0x19a4c116, -1194143544), new int64(0x1e376c08, 0x5141ab53),
new int64(0x2748774c, -544281703), new int64(0x34b0bcb5, -509917016),
new int64(0x391c0cb3, -976659869), new int64(0x4ed8aa4a, -482243893),
new int64(0x5b9cca4f, 0x7763e373), new int64(0x682e6ff3, -692930397),
new int64(0x748f82ee, 0x5defb2fc), new int64(0x78a5636f, 0x43172f60),
new int64(-2067236844, -1578062990), new int64(-1933114872, 0x1a6439ec),
new int64(-1866530822, 0x23631e28), new int64(-1538233109, -561857047),
new int64(-1090935817, -1295615723), new int64(-965641998, -479046869),
new int64(-903397682, -366583396), new int64(-779700025, 0x21c0c207),
new int64(-354779690, -840897762), new int64(-176337025, -294727304),
new int64(0x6f067aa, 0x72176fba), new int64(0xa637dc5, -1563912026),
new int64(0x113f9804, -1090974290), new int64(0x1b710b35, 0x131c471b),
new int64(0x28db77f5, 0x23047d84), new int64(0x32caab7b, 0x40c72493),
new int64(0x3c9ebe0a, 0x15c9bebc), new int64(0x431d67c4, -1676669620),
new int64(0x4cc5d4be, -885112138), new int64(0x597f299c, -60457430),
new int64(0x5fcb6fab, 0x3ad6faec), new int64(0x6c44198c, 0x4a475817));
 }

 //Initial hash values
 var H = new Array(
new int64(0x6a09e667, -205731576),
new int64(-1150833019, -2067093701),
new int64(0x3c6ef372, -23791573),
new int64(-1521486534, 0x5f1d36f1),
new int64(0x510e527f, -1377402159),
new int64(-1694144372, 0x2b3e6c1f),
new int64(0x1f83d9ab, -79577749),
new int64(0x5be0cd19, 0x137e2179));

 var T1 = new int64(0, 0),
  T2 = new int64(0, 0),
  a = new int64(0,0),
  b = new int64(0,0),
  c = new int64(0,0),
  d = new int64(0,0),
  e = new int64(0,0),
  f = new int64(0,0),
  g = new int64(0,0),
  h = new int64(0,0),
  //Temporary variables not specified by the document
  s0 = new int64(0, 0),
  s1 = new int64(0, 0),
  Ch = new int64(0, 0),
  Maj = new int64(0, 0),
  r1 = new int64(0, 0),
  r2 = new int64(0, 0),
  r3 = new int64(0, 0);
 var j, i;
 var W = new Array(80);
 for(i=0; i<80; i++)
  W[i] = new int64(0, 0);

 // append padding to the source string. The format is described in the FIPS.
 x[len >> 5] |= 0x80 << (24 - (len & 0x1f));
 x[((len + 128 >> 10)<< 5) + 31] = len;

 for(i = 0; i<x.length; i+=32) //32 dwords is the block size
 {
  int64copy(a, H[0]);
  int64copy(b, H[1]);
  int64copy(c, H[2]);
  int64copy(d, H[3]);
  int64copy(e, H[4]);
  int64copy(f, H[5]);
  int64copy(g, H[6]);
  int64copy(h, H[7]);

  for(j=0; j<16; j++)
  {
    W[j].h = x[i + 2*j];
    W[j].l = x[i + 2*j + 1];
  }

  for(j=16; j<80; j++)
  {
   //sigma1
   int64rrot(r1, W[j-2], 19);
   int64revrrot(r2, W[j-2], 29);
   int64shr(r3, W[j-2], 6);
   s1.l = r1.l ^ r2.l ^ r3.l;
   s1.h = r1.h ^ r2.h ^ r3.h;
   //sigma0
   int64rrot(r1, W[j-15], 1);
   int64rrot(r2, W[j-15], 8);
   int64shr(r3, W[j-15], 7);
   s0.l = r1.l ^ r2.l ^ r3.l;
   s0.h = r1.h ^ r2.h ^ r3.h;

   int64add4(W[j], s1, W[j-7], s0, W[j-16]);
  }

  for(j = 0; j < 80; j++)
  {
   //Ch
   Ch.l = (e.l & f.l) ^ (~e.l & g.l);
   Ch.h = (e.h & f.h) ^ (~e.h & g.h);

   //Sigma1
   int64rrot(r1, e, 14);
   int64rrot(r2, e, 18);
   int64revrrot(r3, e, 9);
   s1.l = r1.l ^ r2.l ^ r3.l;
   s1.h = r1.h ^ r2.h ^ r3.h;

   //Sigma0
   int64rrot(r1, a, 28);
   int64revrrot(r2, a, 2);
   int64revrrot(r3, a, 7);
   s0.l = r1.l ^ r2.l ^ r3.l;
   s0.h = r1.h ^ r2.h ^ r3.h;

   //Maj
   Maj.l = (a.l & b.l) ^ (a.l & c.l) ^ (b.l & c.l);
   Maj.h = (a.h & b.h) ^ (a.h & c.h) ^ (b.h & c.h);

   int64add5(T1, h, s1, Ch, sha512_k[j], W[j]);
   int64add(T2, s0, Maj);

   int64copy(h, g);
   int64copy(g, f);
   int64copy(f, e);
   int64add(e, d, T1);
   int64copy(d, c);
   int64copy(c, b);
   int64copy(b, a);
   int64add(a, T1, T2);
  }
  int64add(H[0], H[0], a);
  int64add(H[1], H[1], b);
  int64add(H[2], H[2], c);
  int64add(H[3], H[3], d);
  int64add(H[4], H[4], e);
  int64add(H[5], H[5], f);
  int64add(H[6], H[6], g);
  int64add(H[7], H[7], h);
 }

 //represent the hash as an array of 32-bit dwords
 var hash = new Array(16);
 for(i=0; i<8; i++)
 {
  hash[2*i] = H[i].h;
  hash[2*i + 1] = H[i].l;
 }
 return hash;
}

//A constructor for 64-bit numbers
function int64(h, l)
{
 this.h = h;
 this.l = l;
 //this.toString = int64toString;
}

//Copies src into dst, assuming both are 64-bit numbers
function int64copy(dst, src)
{
 dst.h = src.h;
 dst.l = src.l;
}

//Right-rotates a 64-bit number by shift
//Won't handle cases of shift>=32
//The function revrrot() is for that
function int64rrot(dst, x, shift)
{
  dst.l = (x.l >>> shift) | (x.h << (32-shift));
  dst.h = (x.h >>> shift) | (x.l << (32-shift));
}

//Reverses the dwords of the source and then rotates right by shift.
//This is equivalent to rotation by 32+shift
function int64revrrot(dst, x, shift)
{
  dst.l = (x.h >>> shift) | (x.l << (32-shift));
  dst.h = (x.l >>> shift) | (x.h << (32-shift));
}

//Bitwise-shifts right a 64-bit number by shift
//Won't handle shift>=32, but it's never needed in SHA512
function int64shr(dst, x, shift)
{
  dst.l = (x.l >>> shift) | (x.h << (32-shift));
  dst.h = (x.h >>> shift);
}

//Adds two 64-bit numbers
//Like the original implementation, does not rely on 32-bit operations
function int64add(dst, x, y)
{
  var w0 = (x.l & 0xffff) + (y.l & 0xffff);
  var w1 = (x.l >>> 16) + (y.l >>> 16) + (w0 >>> 16);
  var w2 = (x.h & 0xffff) + (y.h & 0xffff) + (w1 >>> 16);
  var w3 = (x.h >>> 16) + (y.h >>> 16) + (w2 >>> 16);
  dst.l = (w0 & 0xffff) | (w1 << 16);
  dst.h = (w2 & 0xffff) | (w3 << 16);
}

//Same, except with 4 addends. Works faster than adding them one by one.
function int64add4(dst, a, b, c, d)
{
  var w0 = (a.l & 0xffff) + (b.l & 0xffff) + (c.l & 0xffff) + (d.l & 0xffff);
  var w1 = (a.l >>> 16) + (b.l >>> 16) + (c.l >>> 16) + (d.l >>> 16) + (w0 >>> 16);
  var w2 = (a.h & 0xffff) + (b.h & 0xffff) + (c.h & 0xffff) + (d.h & 0xffff) + (w1 >>> 16);
  var w3 = (a.h >>> 16) + (b.h >>> 16) + (c.h >>> 16) + (d.h >>> 16) + (w2 >>> 16);
  dst.l = (w0 & 0xffff) | (w1 << 16);
  dst.h = (w2 & 0xffff) | (w3 << 16);
}

//Same, except with 5 addends
function int64add5(dst, a, b, c, d, e)
{
  var w0 = (a.l & 0xffff) + (b.l & 0xffff) + (c.l & 0xffff) + (d.l & 0xffff) + (e.l & 0xffff);
  var w1 = (a.l >>> 16) + (b.l >>> 16) + (c.l >>> 16) + (d.l >>> 16) + (e.l >>> 16) + (w0 >>> 16);
  var w2 = (a.h & 0xffff) + (b.h & 0xffff) + (c.h & 0xffff) + (d.h & 0xffff) + (e.h & 0xffff) + (w1 >>> 16);
  var w3 = (a.h >>> 16) + (b.h >>> 16) + (c.h >>> 16) + (d.h >>> 16) + (e.h >>> 16) + (w2 >>> 16);
  dst.l = (w0 & 0xffff) | (w1 << 16);
  dst.h = (w2 & 0xffff) | (w3 << 16);
}

SHR256加密算法

/*
 * A JavaScript implementation of the Secure Hash Algorithm, SHA-256, as defined
 * in FIPS 180-2
 * Version 2.2 Copyright Angel Marin, Paul Johnston 2000 - 2009.
 * Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
 * Distributed under the BSD License
 * See http://pajhome.org.uk/crypt/md5 for details.
 * Also http://anmar.eu.org/projects/jssha2/
 */

/*
 * 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  */

/*
 * 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_sha256(s)  { return rstr2hex(rstr_sha256(str2rstr_utf8(s))); }
function b64_sha256(s)  { return rstr2b64(rstr_sha256(str2rstr_utf8(s))); }
function any_sha256(s, e) { return rstr2any(rstr_sha256(str2rstr_utf8(s)), e); }
function hex_hmac_sha256(k, d)
 { return rstr2hex(rstr_hmac_sha256(str2rstr_utf8(k), str2rstr_utf8(d))); }
function b64_hmac_sha256(k, d)
 { return rstr2b64(rstr_hmac_sha256(str2rstr_utf8(k), str2rstr_utf8(d))); }
function any_hmac_sha256(k, d, e)
 { return rstr2any(rstr_hmac_sha256(str2rstr_utf8(k), str2rstr_utf8(d)), e); }

/*
 * Perform a simple self-test to see if the VM is working
 */
function sha256_vm_test()
{
 return hex_sha256("abc").toLowerCase() ==
      "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad";
}

/*
 * Calculate the sha256 of a raw string
 */
function rstr_sha256(s)
{
 return binb2rstr(binb_sha256(rstr2binb(s), s.length * 8));
}

/*
 * Calculate the HMAC-sha256 of a key and some data (raw strings)
 */
function rstr_hmac_sha256(key, data)
{
 var bkey = rstr2binb(key);
 if(bkey.length > 16) bkey = binb_sha256(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 = binb_sha256(ipad.concat(rstr2binb(data)), 512 + data.length * 8);
 return binb2rstr(binb_sha256(opad.concat(hash), 512 + 256));
}

/*
 * Convert a raw string to a hex string
 */
function rstr2hex(input)
{
 try { hexcase } catch(e) { hexcase=0; }
 var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
 var output = "";
 var x;
 for(var i = 0; i < input.length; i++)
 {
  x = input.charCodeAt(i);
  output += hex_tab.charAt((x >>> 4) & 0x0F)
      + hex_tab.charAt( x    & 0x0F);
 }
 return output;
}

/*
 * Convert a raw string to a base-64 string
 */
function rstr2b64(input)
{
 try { b64pad } catch(e) { b64pad=''; }
 var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 var output = "";
 var len = input.length;
 for(var i = 0; i < len; i += 3)
 {
  var triplet = (input.charCodeAt(i) << 16)
        | (i + 1 < len ? input.charCodeAt(i+1) << 8 : 0)
        | (i + 2 < len ? input.charCodeAt(i+2)   : 0);
  for(var j = 0; j < 4; j++)
  {
   if(i * 8 + j * 6 > input.length * 8) output += b64pad;
   else output += tab.charAt((triplet >>> 6*(3-j)) & 0x3F);
  }
 }
 return output;
}

/*
 * Convert a raw string to an arbitrary string encoding
 */
function rstr2any(input, encoding)
{
 var divisor = encoding.length;
 var remainders = Array();
 var i, q, x, quotient;

 /* Convert to an array of 16-bit big-endian values, forming the dividend */
 var dividend = Array(Math.ceil(input.length / 2));
 for(i = 0; i < dividend.length; i++)
 {
  dividend[i] = (input.charCodeAt(i * 2) << 8) | input.charCodeAt(i * 2 + 1);
 }

 /*
  * Repeatedly perform a long division. The binary array forms the dividend,
  * the length of the encoding is the divisor. Once computed, the quotient
  * forms the dividend for the next step. We stop when the dividend is zero.
  * All remainders are stored for later use.
  */
 while(dividend.length > 0)
 {
  quotient = Array();
  x = 0;
  for(i = 0; i < dividend.length; i++)
  {
   x = (x << 16) + dividend[i];
   q = Math.floor(x / divisor);
   x -= q * divisor;
   if(quotient.length > 0 || q > 0)
    quotient[quotient.length] = q;
  }
  remainders[remainders.length] = x;
  dividend = quotient;
 }

 /* Convert the remainders to the output string */
 var output = "";
 for(i = remainders.length - 1; i >= 0; i--)
  output += encoding.charAt(remainders[i]);

 /* Append leading zero equivalents */
 var full_length = Math.ceil(input.length * 8 /
                  (Math.log(encoding.length) / Math.log(2)))
 for(i = output.length; i < full_length; i++)
  output = encoding[0] + output;

 return output;
}

/*
 * Encode a string as utf-8.
 * For efficiency, this assumes the input is valid utf-16.
 */
function str2rstr_utf8(input)
{
 var output = "";
 var i = -1;
 var x, y;

 while(++i < input.length)
 {
  /* Decode utf-16 surrogate pairs */
  x = input.charCodeAt(i);
  y = i + 1 < input.length ? input.charCodeAt(i + 1) : 0;
  if(0xD800 <= x && x <= 0xDBFF && 0xDC00 <= y && y <= 0xDFFF)
  {
   x = 0x10000 + ((x & 0x03FF) << 10) + (y & 0x03FF);
   i++;
  }

  /* Encode output as utf-8 */
  if(x <= 0x7F)
   output += String.fromCharCode(x);
  else if(x <= 0x7FF)
   output += String.fromCharCode(0xC0 | ((x >>> 6 ) & 0x1F),
                  0x80 | ( x     & 0x3F));
  else if(x <= 0xFFFF)
   output += String.fromCharCode(0xE0 | ((x >>> 12) & 0x0F),
                  0x80 | ((x >>> 6 ) & 0x3F),
                  0x80 | ( x     & 0x3F));
  else if(x <= 0x1FFFFF)
   output += String.fromCharCode(0xF0 | ((x >>> 18) & 0x07),
                  0x80 | ((x >>> 12) & 0x3F),
                  0x80 | ((x >>> 6 ) & 0x3F),
                  0x80 | ( x     & 0x3F));
 }
 return output;
}

/*
 * Encode a string as utf-16
 */
function str2rstr_utf16le(input)
{
 var output = "";
 for(var i = 0; i < input.length; i++)
  output += String.fromCharCode( input.charCodeAt(i)    & 0xFF,
                 (input.charCodeAt(i) >>> 8) & 0xFF);
 return output;
}

function str2rstr_utf16be(input)
{
 var output = "";
 for(var i = 0; i < input.length; i++)
  output += String.fromCharCode((input.charCodeAt(i) >>> 8) & 0xFF,
                  input.charCodeAt(i)    & 0xFF);
 return output;
}

/*
 * Convert a raw string to an array of big-endian words
 * Characters >255 have their high-byte silently ignored.
 */
function rstr2binb(input)
{
 var output = Array(input.length >> 2);
 for(var i = 0; i < output.length; i++)
  output[i] = 0;
 for(var i = 0; i < input.length * 8; i += 8)
  output[i>>5] |= (input.charCodeAt(i / 8) & 0xFF) << (24 - i % 32);
 return output;
}

/*
 * Convert an array of big-endian words to a string
 */
function binb2rstr(input)
{
 var output = "";
 for(var i = 0; i < input.length * 32; i += 8)
  output += String.fromCharCode((input[i>>5] >>> (24 - i % 32)) & 0xFF);
 return output;
}

/*
 * Main sha256 function, with its support functions
 */
function sha256_S (X, n) {return ( X >>> n ) | (X << (32 - n));}
function sha256_R (X, n) {return ( X >>> n );}
function sha256_Ch(x, y, z) {return ((x & y) ^ ((~x) & z));}
function sha256_Maj(x, y, z) {return ((x & y) ^ (x & z) ^ (y & z));}
function sha256_Sigma0256(x) {return (sha256_S(x, 2) ^ sha256_S(x, 13) ^ sha256_S(x, 22));}
function sha256_Sigma1256(x) {return (sha256_S(x, 6) ^ sha256_S(x, 11) ^ sha256_S(x, 25));}
function sha256_Gamma0256(x) {return (sha256_S(x, 7) ^ sha256_S(x, 18) ^ sha256_R(x, 3));}
function sha256_Gamma1256(x) {return (sha256_S(x, 17) ^ sha256_S(x, 19) ^ sha256_R(x, 10));}
function sha256_Sigma0512(x) {return (sha256_S(x, 28) ^ sha256_S(x, 34) ^ sha256_S(x, 39));}
function sha256_Sigma1512(x) {return (sha256_S(x, 14) ^ sha256_S(x, 18) ^ sha256_S(x, 41));}
function sha256_Gamma0512(x) {return (sha256_S(x, 1) ^ sha256_S(x, 8) ^ sha256_R(x, 7));}
function sha256_Gamma1512(x) {return (sha256_S(x, 19) ^ sha256_S(x, 61) ^ sha256_R(x, 6));}

var sha256_K = new Array
(
 1116352408, 1899447441, -1245643825, -373957723, 961987163, 1508970993,
 -1841331548, -1424204075, -670586216, 310598401, 607225278, 1426881987,
 1925078388, -2132889090, -1680079193, -1046744716, -459576895, -272742522,
 264347078, 604807628, 770255983, 1249150122, 1555081692, 1996064986,
 -1740746414, -1473132947, -1341970488, -1084653625, -958395405, -710438585,
 113926993, 338241895, 666307205, 773529912, 1294757372, 1396182291,
 1695183700, 1986661051, -2117940946, -1838011259, -1564481375, -1474664885,
 -1035236496, -949202525, -778901479, -694614492, -200395387, 275423344,
 430227734, 506948616, 659060556, 883997877, 958139571, 1322822218,
 1537002063, 1747873779, 1955562222, 2024104815, -2067236844, -1933114872,
 -1866530822, -1538233109, -1090935817, -965641998
);

function binb_sha256(m, l)
{
 var HASH = new Array(1779033703, -1150833019, 1013904242, -1521486534,
            1359893119, -1694144372, 528734635, 1541459225);
 var W = new Array(64);
 var a, b, c, d, e, f, g, h;
 var i, j, T1, T2;

 /* append padding */
 m[l >> 5] |= 0x80 << (24 - l % 32);
 m[((l + 64 >> 9) << 4) + 15] = l;

 for(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(j = 0; j < 64; j++)
  {
   if (j < 16) W[j] = m[j + i];
   else W[j] = safe_add(safe_add(safe_add(sha256_Gamma1256(W[j - 2]), W[j - 7]),
                      sha256_Gamma0256(W[j - 15])), W[j - 16]);

   T1 = safe_add(safe_add(safe_add(safe_add(h, sha256_Sigma1256(e)), sha256_Ch(e, f, g)),
                             sha256_K[j]), W[j]);
   T2 = safe_add(sha256_Sigma0256(a), sha256_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 safe_add (x, y)
{
 var lsw = (x & 0xFFFF) + (y & 0xFFFF);
 var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
 return (msw << 16) | (lsw & 0xFFFF);
}