JavaScript SHA-256 Encryption algorithm detailed code _javascript tips

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/*
 * 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);
}  

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