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AES Encryption/Decryption Javascript

InfectedPacket Aug 21st, 2015 228 Never
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  1. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  2. /*  AES implementation in JavaScript (c) Chris Veness 2005-2011                                   */
  3. /*   - see http://csrc.nist.gov/publications/PubsFIPS.html#197                                    */
  4. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  5.  
  6. var Aes = {};  // Aes namespace
  7.  
  8. /**
  9.  * AES Cipher function: encrypt 'input' state with Rijndael algorithm
  10.  *   applies Nr rounds (10/12/14) using key schedule w for 'add round key' stage
  11.  *
  12.  * @param {Number[]} input 16-byte (128-bit) input state array
  13.  * @param {Number[][]} w   Key schedule as 2D byte-array (Nr+1 x Nb bytes)
  14.  * @returns {Number[]}     Encrypted output state array
  15.  */
  16. Aes.cipher = function(input, w) {    // main Cipher function [§5.1]
  17.   var Nb = 4;               // block size (in words): no of columns in state (fixed at 4 for AES)
  18.   var Nr = w.length/Nb - 1; // no of rounds: 10/12/14 for 128/192/256-bit keys
  19.  
  20.   var state = [[],[],[],[]];  // initialise 4xNb byte-array 'state' with input [§3.4]
  21.   for (var i=0; i<4*Nb; i++) state[i%4][Math.floor(i/4)] = input[i];
  22.  
  23.   state = Aes.addRoundKey(state, w, 0, Nb);
  24.  
  25.   for (var round=1; round<Nr; round++) {
  26.     state = Aes.subBytes(state, Nb);
  27.     state = Aes.shiftRows(state, Nb);
  28.     state = Aes.mixColumns(state, Nb);
  29.     state = Aes.addRoundKey(state, w, round, Nb);
  30.   }
  31.  
  32.   state = Aes.subBytes(state, Nb);
  33.   state = Aes.shiftRows(state, Nb);
  34.   state = Aes.addRoundKey(state, w, Nr, Nb);
  35.  
  36.   var output = new Array(4*Nb);  // convert state to 1-d array before returning [§3.4]
  37.   for (var i=0; i<4*Nb; i++) output[i] = state[i%4][Math.floor(i/4)];
  38.   return output;
  39. }
  40.  
  41. /**
  42.  * Perform Key Expansion to generate a Key Schedule
  43.  *
  44.  * @param {Number[]} key Key as 16/24/32-byte array
  45.  * @returns {Number[][]} Expanded key schedule as 2D byte-array (Nr+1 x Nb bytes)
  46.  */
  47. Aes.keyExpansion = function(key) {  // generate Key Schedule (byte-array Nr+1 x Nb) from Key [§5.2]
  48.   var Nb = 4;            // block size (in words): no of columns in state (fixed at 4 for AES)
  49.   var Nk = key.length/4  // key length (in words): 4/6/8 for 128/192/256-bit keys
  50.   var Nr = Nk + 6;       // no of rounds: 10/12/14 for 128/192/256-bit keys
  51.  
  52.   var w = new Array(Nb*(Nr+1));
  53.   var temp = new Array(4);
  54.  
  55.   for (var i=0; i<Nk; i++) {
  56.     var r = [key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]];
  57.     w[i] = r;
  58.   }
  59.  
  60.   for (var i=Nk; i<(Nb*(Nr+1)); i++) {
  61.     w[i] = new Array(4);
  62.     for (var t=0; t<4; t++) temp[t] = w[i-1][t];
  63.     if (i % Nk == 0) {
  64.       temp = Aes.subWord(Aes.rotWord(temp));
  65.       for (var t=0; t<4; t++) temp[t] ^= Aes.rCon[i/Nk][t];
  66.     } else if (Nk > 6 && i%Nk == 4) {
  67.       temp = Aes.subWord(temp);
  68.     }
  69.     for (var t=0; t<4; t++) w[i][t] = w[i-Nk][t] ^ temp[t];
  70.   }
  71.  
  72.   return w;
  73. }
  74.  
  75. /*
  76.  * ---- remaining routines are private, not called externally ----
  77.  */
  78.  
  79. Aes.subBytes = function(s, Nb) {    // apply SBox to state S [§5.1.1]
  80.   for (var r=0; r<4; r++) {
  81.     for (var c=0; c<Nb; c++) s[r][c] = Aes.sBox[s[r][c]];
  82.   }
  83.   return s;
  84. }
  85.  
  86. Aes.shiftRows = function(s, Nb) {    // shift row r of state S left by r bytes [§5.1.2]
  87.   var t = new Array(4);
  88.   for (var r=1; r<4; r++) {
  89.     for (var c=0; c<4; c++) t[c] = s[r][(c+r)%Nb];  // shift into temp copy
  90.     for (var c=0; c<4; c++) s[r][c] = t[c];         // and copy back
  91.   }          // note that this will work for Nb=4,5,6, but not 7,8 (always 4 for AES):
  92.   return s;  // see asmaes.sourceforge.net/rijndael/rijndaelImplementation.pdf
  93. }
  94.  
  95. Aes.mixColumns = function(s, Nb) {   // combine bytes of each col of state S [§5.1.3]
  96.   for (var c=0; c<4; c++) {
  97.     var a = new Array(4);  // 'a' is a copy of the current column from 's'
  98.     var b = new Array(4);  // 'b' is a•{02} in GF(2^8)
  99.     for (var i=0; i<4; i++) {
  100.       a[i] = s[i][c];
  101.       b[i] = s[i][c]&0x80 ? s[i][c]<<1 ^ 0x011b : s[i][c]<<1;
  102.  
  103.     }
  104.     // a[n] ^ b[n] is a•{03} in GF(2^8)
  105.     s[0][c] = b[0] ^ a[1] ^ b[1] ^ a[2] ^ a[3]; // 2*a0 + 3*a1 + a2 + a3
  106.     s[1][c] = a[0] ^ b[1] ^ a[2] ^ b[2] ^ a[3]; // a0 * 2*a1 + 3*a2 + a3
  107.     s[2][c] = a[0] ^ a[1] ^ b[2] ^ a[3] ^ b[3]; // a0 + a1 + 2*a2 + 3*a3
  108.     s[3][c] = a[0] ^ b[0] ^ a[1] ^ a[2] ^ b[3]; // 3*a0 + a1 + a2 + 2*a3
  109.   }
  110.   return s;
  111. }
  112.  
  113. Aes.addRoundKey = function(state, w, rnd, Nb) {  // xor Round Key into state S [§5.1.4]
  114.   for (var r=0; r<4; r++) {
  115.     for (var c=0; c<Nb; c++) state[r][c] ^= w[rnd*4+c][r];
  116.   }
  117.   return state;
  118. }
  119.  
  120. Aes.subWord = function(w) {    // apply SBox to 4-byte word w
  121.   for (var i=0; i<4; i++) w[i] = Aes.sBox[w[i]];
  122.   return w;
  123. }
  124.  
  125. Aes.rotWord = function(w) {    // rotate 4-byte word w left by one byte
  126.   var tmp = w[0];
  127.   for (var i=0; i<3; i++) w[i] = w[i+1];
  128.   w[3] = tmp;
  129.   return w;
  130. }
  131.  
  132. // sBox is pre-computed multiplicative inverse in GF(2^8) used in subBytes and keyExpansion [§5.1.1]
  133. Aes.sBox =  [0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
  134.              0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
  135.              0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
  136.              0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
  137.              0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
  138.              0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
  139.              0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
  140.              0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
  141.              0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
  142.              0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
  143.              0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
  144.              0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
  145.              0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
  146.              0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
  147.              0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
  148.              0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16];
  149.  
  150. // rCon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2]
  151. Aes.rCon = [ [0x00, 0x00, 0x00, 0x00],
  152.              [0x01, 0x00, 0x00, 0x00],
  153.              [0x02, 0x00, 0x00, 0x00],
  154.              [0x04, 0x00, 0x00, 0x00],
  155.              [0x08, 0x00, 0x00, 0x00],
  156.              [0x10, 0x00, 0x00, 0x00],
  157.              [0x20, 0x00, 0x00, 0x00],
  158.              [0x40, 0x00, 0x00, 0x00],
  159.              [0x80, 0x00, 0x00, 0x00],
  160.              [0x1b, 0x00, 0x00, 0x00],
  161.              [0x36, 0x00, 0x00, 0x00] ];
  162.  
  163.  
  164. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  165. /*  AES Counter-mode implementation in JavaScript (c) Chris Veness 2005-2011                      */
  166. /*   - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf                       */
  167. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  168.  
  169. Aes.Ctr = {};  // Aes.Ctr namespace: a subclass or extension of Aes
  170.  
  171. /**
  172.  * Encrypt a text using AES encryption in Counter mode of operation
  173.  *
  174.  * Unicode multi-byte character safe
  175.  *
  176.  * @param {String} plaintext Source text to be encrypted
  177.  * @param {String} password  The password to use to generate a key
  178.  * @param {Number} nBits     Number of bits to be used in the key (128, 192, or 256)
  179.  * @returns {string}         Encrypted text
  180.  */
  181. Aes.Ctr.encrypt = function(plaintext, password, nBits) {
  182.   var blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
  183.   if (!(nBits==128 || nBits==192 || nBits==256)) return '';  // standard allows 128/192/256 bit keys
  184.   plaintext = Utf8.encode(plaintext);
  185.   password = Utf8.encode(password);
  186.   //var t = new Date();  // timer
  187.        
  188.   // use AES itself to encrypt password to get cipher key (using plain password as source for key
  189.   // expansion) - gives us well encrypted key (though hashed key might be preferred for prod'n use)
  190.   var nBytes = nBits/8;  // no bytes in key (16/24/32)
  191.   var pwBytes = new Array(nBytes);
  192.   for (var i=0; i<nBytes; i++) {  // use 1st 16/24/32 chars of password for key
  193.     pwBytes[i] = isNaN(password.charCodeAt(i)) ? 0 : password.charCodeAt(i);
  194.   }
  195.   var key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes));  // gives us 16-byte key
  196.   key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long
  197.  
  198.   // initialise 1st 8 bytes of counter block with nonce (NIST SP800-38A §B.2): [0-1] = millisec,
  199.   // [2-3] = random, [4-7] = seconds, together giving full sub-millisec uniqueness up to Feb 2106
  200.   var counterBlock = new Array(blockSize);
  201.  
  202.   var nonce = (new Date()).getTime();  // timestamp: milliseconds since 1-Jan-1970
  203.   var nonceMs = nonce%1000;
  204.   var nonceSec = Math.floor(nonce/1000);
  205.   var nonceRnd = Math.floor(Math.random()*0xffff);
  206.  
  207.   for (var i=0; i<2; i++) counterBlock[i]   = (nonceMs  >>> i*8) & 0xff;
  208.   for (var i=0; i<2; i++) counterBlock[i+2] = (nonceRnd >>> i*8) & 0xff;
  209.   for (var i=0; i<4; i++) counterBlock[i+4] = (nonceSec >>> i*8) & 0xff;
  210.  
  211.   // and convert it to a string to go on the front of the ciphertext
  212.   var ctrTxt = '';
  213.   for (var i=0; i<8; i++) ctrTxt += String.fromCharCode(counterBlock[i]);
  214.  
  215.   // generate key schedule - an expansion of the key into distinct Key Rounds for each round
  216.   var keySchedule = Aes.keyExpansion(key);
  217.  
  218.   var blockCount = Math.ceil(plaintext.length/blockSize);
  219.   var ciphertxt = new Array(blockCount);  // ciphertext as array of strings
  220.  
  221.   for (var b=0; b<blockCount; b++) {
  222.     // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
  223.     // done in two stages for 32-bit ops: using two words allows us to go past 2^32 blocks (68GB)
  224.     for (var c=0; c<4; c++) counterBlock[15-c] = (b >>> c*8) & 0xff;
  225.     for (var c=0; c<4; c++) counterBlock[15-c-4] = (b/0x100000000 >>> c*8)
  226.  
  227.     var cipherCntr = Aes.cipher(counterBlock, keySchedule);  // -- encrypt counter block --
  228.    
  229.     // block size is reduced on final block
  230.     var blockLength = b<blockCount-1 ? blockSize : (plaintext.length-1)%blockSize+1;
  231.     var cipherChar = new Array(blockLength);
  232.    
  233.     for (var i=0; i<blockLength; i++) {  // -- xor plaintext with ciphered counter char-by-char --
  234.       cipherChar[i] = cipherCntr[i] ^ plaintext.charCodeAt(b*blockSize+i);
  235.       cipherChar[i] = String.fromCharCode(cipherChar[i]);
  236.     }
  237.     ciphertxt[b] = cipherChar.join('');
  238.   }
  239.  
  240.   // Array.join is more efficient than repeated string concatenation in IE
  241.   var ciphertext = ctrTxt + ciphertxt.join('');
  242.   ciphertext = Base64.encode(ciphertext);  // encode in base64
  243.  
  244.   //alert((new Date()) - t);
  245.   return ciphertext;
  246. }
  247.  
  248. /**
  249.  * Decrypt a text encrypted by AES in counter mode of operation
  250.  *
  251.  * @param {String} ciphertext Source text to be encrypted
  252.  * @param {String} password   The password to use to generate a key
  253.  * @param {Number} nBits      Number of bits to be used in the key (128, 192, or 256)
  254.  * @returns {String}          Decrypted text
  255.  */
  256. Aes.Ctr.decrypt = function(ciphertext, password, nBits) {
  257.   var blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
  258.   if (!(nBits==128 || nBits==192 || nBits==256)) return '';  // standard allows 128/192/256 bit keys
  259.   ciphertext = Base64.decode(ciphertext);
  260.   password = Utf8.encode(password);
  261.   //var t = new Date();  // timer
  262.  
  263.   // use AES to encrypt password (mirroring encrypt routine)
  264.   var nBytes = nBits/8;  // no bytes in key
  265.   var pwBytes = new Array(nBytes);
  266.   for (var i=0; i<nBytes; i++) {
  267.     pwBytes[i] = isNaN(password.charCodeAt(i)) ? 0 : password.charCodeAt(i);
  268.   }
  269.   var key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes));
  270.   key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long
  271.  
  272.   // recover nonce from 1st 8 bytes of ciphertext
  273.   var counterBlock = new Array(8);
  274.   ctrTxt = ciphertext.slice(0, 8);
  275.   for (var i=0; i<8; i++) counterBlock[i] = ctrTxt.charCodeAt(i);
  276.  
  277.   // generate key schedule
  278.   var keySchedule = Aes.keyExpansion(key);
  279.  
  280.   // separate ciphertext into blocks (skipping past initial 8 bytes)
  281.   var nBlocks = Math.ceil((ciphertext.length-8) / blockSize);
  282.   var ct = new Array(nBlocks);
  283.   for (var b=0; b<nBlocks; b++) ct[b] = ciphertext.slice(8+b*blockSize, 8+b*blockSize+blockSize);
  284.   ciphertext = ct;  // ciphertext is now array of block-length strings
  285.  
  286.   // plaintext will get generated block-by-block into array of block-length strings
  287.   var plaintxt = new Array(ciphertext.length);
  288.  
  289.   for (var b=0; b<nBlocks; b++) {
  290.     // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
  291.     for (var c=0; c<4; c++) counterBlock[15-c] = ((b) >>> c*8) & 0xff;
  292.     for (var c=0; c<4; c++) counterBlock[15-c-4] = (((b+1)/0x100000000-1) >>> c*8) & 0xff;
  293.  
  294.     var cipherCntr = Aes.cipher(counterBlock, keySchedule);  // encrypt counter block
  295.  
  296.     var plaintxtByte = new Array(ciphertext[b].length);
  297.     for (var i=0; i<ciphertext[b].length; i++) {
  298.       // -- xor plaintxt with ciphered counter byte-by-byte --
  299.       plaintxtByte[i] = cipherCntr[i] ^ ciphertext[b].charCodeAt(i);
  300.       plaintxtByte[i] = String.fromCharCode(plaintxtByte[i]);
  301.     }
  302.     plaintxt[b] = plaintxtByte.join('');
  303.   }
  304.  
  305.   // join array of blocks into single plaintext string
  306.   var plaintext = plaintxt.join('');
  307.   plaintext = Utf8.decode(plaintext);  // decode from UTF8 back to Unicode multi-byte chars
  308.  
  309.   //alert((new Date()) - t);
  310.   return plaintext;
  311. }
  312.  
  313.  
  314. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  315. /*  Base64 class: Base 64 encoding / decoding (c) Chris Veness 2002-2011                          */
  316. /*    note: depends on Utf8 class                                                                 */
  317. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  318.  
  319. var Base64 = {};  // Base64 namespace
  320.  
  321. Base64.code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
  322.  
  323. /**
  324.  * Encode string into Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648]
  325.  * (instance method extending String object). As per RFC 4648, no newlines are added.
  326.  *
  327.  * @param {String} str The string to be encoded as base-64
  328.  * @param {Boolean} [utf8encode=false] Flag to indicate whether str is Unicode string to be encoded
  329.  *   to UTF8 before conversion to base64; otherwise string is assumed to be 8-bit characters
  330.  * @returns {String} Base64-encoded string
  331.  */
  332. Base64.encode = function(str, utf8encode) {  // http://tools.ietf.org/html/rfc4648
  333.   utf8encode =  (typeof utf8encode == 'undefined') ? false : utf8encode;
  334.   var o1, o2, o3, bits, h1, h2, h3, h4, e=[], pad = '', c, plain, coded;
  335.   var b64 = Base64.code;
  336.    
  337.   plain = utf8encode ? str.encodeUTF8() : str;
  338.  
  339.   c = plain.length % 3;  // pad string to length of multiple of 3
  340.   if (c > 0) { while (c++ < 3) { pad += '='; plain += '\0'; } }
  341.   // note: doing padding here saves us doing special-case packing for trailing 1 or 2 chars
  342.    
  343.   for (c=0; c<plain.length; c+=3) {  // pack three octets into four hexets
  344.     o1 = plain.charCodeAt(c);
  345.     o2 = plain.charCodeAt(c+1);
  346.     o3 = plain.charCodeAt(c+2);
  347.      
  348.     bits = o1<<16 | o2<<8 | o3;
  349.      
  350.     h1 = bits>>18 & 0x3f;
  351.     h2 = bits>>12 & 0x3f;
  352.     h3 = bits>>6 & 0x3f;
  353.     h4 = bits & 0x3f;
  354.  
  355.     // use hextets to index into code string
  356.     e[c/3] = b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
  357.   }
  358.   coded = e.join('');  // join() is far faster than repeated string concatenation in IE
  359.  
  360.   // replace 'A's from padded nulls with '='s
  361.   coded = coded.slice(0, coded.length-pad.length) + pad;
  362.    
  363.   return coded;
  364. }
  365.  
  366. /**
  367.  * Decode string from Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648]
  368.  * (instance method extending String object). As per RFC 4648, newlines are not catered for.
  369.  *
  370.  * @param {String} str The string to be decoded from base-64
  371.  * @param {Boolean} [utf8decode=false] Flag to indicate whether str is Unicode string to be decoded
  372.  *   from UTF8 after conversion from base64
  373.  * @returns {String} decoded string
  374.  */
  375. Base64.decode = function(str, utf8decode) {
  376.   utf8decode =  (typeof utf8decode == 'undefined') ? false : utf8decode;
  377.   var o1, o2, o3, h1, h2, h3, h4, bits, d=[], plain, coded;
  378.   var b64 = Base64.code;
  379.  
  380.   coded = utf8decode ? str.decodeUTF8() : str;
  381.  
  382.  
  383.   for (var c=0; c<coded.length; c+=4) {  // unpack four hexets into three octets
  384.     h1 = b64.indexOf(coded.charAt(c));
  385.     h2 = b64.indexOf(coded.charAt(c+1));
  386.     h3 = b64.indexOf(coded.charAt(c+2));
  387.     h4 = b64.indexOf(coded.charAt(c+3));
  388.      
  389.     bits = h1<<18 | h2<<12 | h3<<6 | h4;
  390.      
  391.     o1 = bits>>>16 & 0xff;
  392.     o2 = bits>>>8 & 0xff;
  393.     o3 = bits & 0xff;
  394.    
  395.     d[c/4] = String.fromCharCode(o1, o2, o3);
  396.     // check for padding
  397.     if (h4 == 0x40) d[c/4] = String.fromCharCode(o1, o2);
  398.     if (h3 == 0x40) d[c/4] = String.fromCharCode(o1);
  399.   }
  400.   plain = d.join('');  // join() is far faster than repeated string concatenation in IE
  401.    
  402.   return utf8decode ? plain.decodeUTF8() : plain;
  403. }
  404.  
  405.  
  406. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  407. /*  Utf8 class: encode / decode between multi-byte Unicode characters and UTF-8 multiple          */
  408. /*              single-byte character encoding (c) Chris Veness 2002-2011                         */
  409. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  410.  
  411. var Utf8 = {};  // Utf8 namespace
  412.  
  413. /**
  414.  * Encode multi-byte Unicode string into utf-8 multiple single-byte characters
  415.  * (BMP / basic multilingual plane only)
  416.  *
  417.  * Chars in range U+0080 - U+07FF are encoded in 2 chars, U+0800 - U+FFFF in 3 chars
  418.  *
  419.  * @param {String} strUni Unicode string to be encoded as UTF-8
  420.  * @returns {String} encoded string
  421.  */
  422. Utf8.encode = function(strUni) {
  423.   // use regular expressions & String.replace callback function for better efficiency
  424.   // than procedural approaches
  425.   var strUtf = strUni.replace(
  426.       /[\u0080-\u07ff]/g,  // U+0080 - U+07FF => 2 bytes 110yyyyy, 10zzzzzz
  427.       function(c) {
  428.         var cc = c.charCodeAt(0);
  429.         return String.fromCharCode(0xc0 | cc>>6, 0x80 | cc&0x3f); }
  430.     );
  431.   strUtf = strUtf.replace(
  432.       /[\u0800-\uffff]/g,  // U+0800 - U+FFFF => 3 bytes 1110xxxx, 10yyyyyy, 10zzzzzz
  433.       function(c) {
  434.         var cc = c.charCodeAt(0);
  435.         return String.fromCharCode(0xe0 | cc>>12, 0x80 | cc>>6&0x3F, 0x80 | cc&0x3f); }
  436.     );
  437.   return strUtf;
  438. }
  439.  
  440. /**
  441.  * Decode utf-8 encoded string back into multi-byte Unicode characters
  442.  *
  443.  * @param {String} strUtf UTF-8 string to be decoded back to Unicode
  444.  * @returns {String} decoded string
  445.  */
  446. Utf8.decode = function(strUtf) {
  447.   // note: decode 3-byte chars first as decoded 2-byte strings could appear to be 3-byte char!
  448.   var strUni = strUtf.replace(
  449.       /[\u00e0-\u00ef][\u0080-\u00bf][\u0080-\u00bf]/g,  // 3-byte chars
  450.       function(c) {  // (note parentheses for precence)
  451.         var cc = ((c.charCodeAt(0)&0x0f)<<12) | ((c.charCodeAt(1)&0x3f)<<6) | ( c.charCodeAt(2)&0x3f);
  452.         return String.fromCharCode(cc); }
  453.     );
  454.   strUni = strUni.replace(
  455.       /[\u00c0-\u00df][\u0080-\u00bf]/g,                 // 2-byte chars
  456.       function(c) {  // (note parentheses for precence)
  457.         var cc = (c.charCodeAt(0)&0x1f)<<6 | c.charCodeAt(1)&0x3f;
  458.         return String.fromCharCode(cc); }
  459.     );
  460.   return strUni;
  461. }
  462.  
  463. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
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