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1/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
2
3/*
4 * AES Cipher function: encrypt 'input' with Rijndael algorithm
5 *
6 *   takes   byte-array 'input' (16 bytes)
7 *           2D byte-array key schedule 'w' (Nr+1 x Nb bytes)
8 *
9 *   applies Nr rounds (10/12/14) using key schedule w for 'add round key' stage
10 *
11 *   returns byte-array encrypted value (16 bytes)
12 */
13function Cipher(input, w) {    // main Cipher function [§5.1]
14  var Nb = 4;               // block size (in words): no of columns in state (fixed at 4 for AES)
15  var Nr = w.length/Nb - 1; // no of rounds: 10/12/14 for 128/192/256-bit keys
16
17  var state = [[],[],[],[]];  // initialise 4xNb byte-array 'state' with input [§3.4]
18  for (var i=0; i<4*Nb; i++) state[i%4][Math.floor(i/4)] = input[i];
19
20  state = AddRoundKey(state, w, 0, Nb);
21
22  for (var round=1; round<Nr; round++) {
23    state = SubBytes(state, Nb);
24    state = ShiftRows(state, Nb);
25    state = MixColumns(state, Nb);
26    state = AddRoundKey(state, w, round, Nb);
27  }
28
29  state = SubBytes(state, Nb);
30  state = ShiftRows(state, Nb);
31  state = AddRoundKey(state, w, Nr, Nb);
32
33  var output = new Array(4*Nb);  // convert state to 1-d array before returning [§3.4]
34  for (var i=0; i<4*Nb; i++) output[i] = state[i%4][Math.floor(i/4)];
35  return output;
36}
37
38
39function SubBytes(s, Nb) {    // apply SBox to state S [§5.1.1]
40  for (var r=0; r<4; r++) {
41    for (var c=0; c<Nb; c++) s[r][c] = Sbox[s[r][c]];
42  }
43  return s;
44}
45
46
47function ShiftRows(s, Nb) {    // shift row r of state S left by r bytes [§5.1.2]
48  var t = new Array(4);
49  for (var r=1; r<4; r++) {
50    for (var c=0; c<4; c++) t[c] = s[r][(c+r)%Nb];  // shift into temp copy
51    for (var c=0; c<4; c++) s[r][c] = t[c];         // and copy back
52  }          // note that this will work for Nb=4,5,6, but not 7,8 (always 4 for AES):
53  return s;  // see fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.311.pdf
54}
55
56
57function MixColumns(s, Nb) {   // combine bytes of each col of state S [§5.1.3]
58  for (var c=0; c<4; c++) {
59    var a = new Array(4);  // 'a' is a copy of the current column from 's'
60    var b = new Array(4);  // 'b' is a•{02} in GF(2^8)
61    for (var i=0; i<4; i++) {
62      a[i] = s[i][c];
63      b[i] = s[i][c]&0x80 ? s[i][c]<<1 ^ 0x011b : s[i][c]<<1;
64    }
65    // a[n] ^ b[n] is a•{03} in GF(2^8)
66    s[0][c] = b[0] ^ a[1] ^ b[1] ^ a[2] ^ a[3]; // 2*a0 + 3*a1 + a2 + a3
67    s[1][c] = a[0] ^ b[1] ^ a[2] ^ b[2] ^ a[3]; // a0 * 2*a1 + 3*a2 + a3
68    s[2][c] = a[0] ^ a[1] ^ b[2] ^ a[3] ^ b[3]; // a0 + a1 + 2*a2 + 3*a3
69    s[3][c] = a[0] ^ b[0] ^ a[1] ^ a[2] ^ b[3]; // 3*a0 + a1 + a2 + 2*a3
70  }
71  return s;
72}
73
74
75function AddRoundKey(state, w, rnd, Nb) {  // xor Round Key into state S [§5.1.4]
76  for (var r=0; r<4; r++) {
77    for (var c=0; c<Nb; c++) state[r][c] ^= w[rnd*4+c][r];
78  }
79  return state;
80}
81
82
83function KeyExpansion(key) {  // generate Key Schedule (byte-array Nr+1 x Nb) from Key [§5.2]
84  var Nb = 4;            // block size (in words): no of columns in state (fixed at 4 for AES)
85  var Nk = key.length/4  // key length (in words): 4/6/8 for 128/192/256-bit keys
86  var Nr = Nk + 6;       // no of rounds: 10/12/14 for 128/192/256-bit keys
87
88  var w = new Array(Nb*(Nr+1));
89  var temp = new Array(4);
90
91  for (var i=0; i<Nk; i++) {
92    var r = [key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]];
93    w[i] = r;
94  }
95
96  for (var i=Nk; i<(Nb*(Nr+1)); i++) {
97    w[i] = new Array(4);
98    for (var t=0; t<4; t++) temp[t] = w[i-1][t];
99    if (i % Nk == 0) {
100      temp = SubWord(RotWord(temp));
101      for (var t=0; t<4; t++) temp[t] ^= Rcon[i/Nk][t];
102    } else if (Nk > 6 && i%Nk == 4) {
103      temp = SubWord(temp);
104    }
105    for (var t=0; t<4; t++) w[i][t] = w[i-Nk][t] ^ temp[t];
106  }
107
108  return w;
109}
110
111function SubWord(w) {    // apply SBox to 4-byte word w
112  for (var i=0; i<4; i++) w[i] = Sbox[w[i]];
113  return w;
114}
115
116function RotWord(w) {    // rotate 4-byte word w left by one byte
117  w[4] = w[0];
118  for (var i=0; i<4; i++) w[i] = w[i+1];
119  return w;
120}
121
122
123// Sbox is pre-computed multiplicative inverse in GF(2^8) used in SubBytes and KeyExpansion [§5.1.1]
124var Sbox =  [0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
125             0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
126             0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
127             0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
128             0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
129             0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
130             0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
131             0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
132             0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
133             0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
134             0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
135             0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
136             0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
137             0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
138             0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
139             0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16];
140
141// Rcon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2]
142var Rcon = [ [0x00, 0x00, 0x00, 0x00],
143             [0x01, 0x00, 0x00, 0x00],
144             [0x02, 0x00, 0x00, 0x00],
145             [0x04, 0x00, 0x00, 0x00],
146             [0x08, 0x00, 0x00, 0x00],
147             [0x10, 0x00, 0x00, 0x00],
148             [0x20, 0x00, 0x00, 0x00],
149             [0x40, 0x00, 0x00, 0x00],
150             [0x80, 0x00, 0x00, 0x00],
151             [0x1b, 0x00, 0x00, 0x00],
152             [0x36, 0x00, 0x00, 0x00] ];
153
154
155/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
156
157/*
158 * Use AES to encrypt 'plaintext' with 'password' using 'nBits' key, in 'Counter' mode of operation
159 *                           - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
160 *   for each block
161 *   - outputblock = cipher(counter, key)
162 *   - cipherblock = plaintext xor outputblock
163 */
164function AESEncryptCtr(plaintext, password, nBits) {
165  if (!(nBits==128 || nBits==192 || nBits==256)) return '';  // standard allows 128/192/256 bit keys
166
167  // for this example script, generate the key by applying Cipher to 1st 16/24/32 chars of password;
168  // for real-world applications, a more secure approach would be to hash the password e.g. with SHA-1
169  var nBytes = nBits/8;  // no bytes in key
170  var pwBytes = new Array(nBytes);
171  for (var i=0; i<nBytes; i++) pwBytes[i] = password.charCodeAt(i) & 0xff;
172  var key = Cipher(pwBytes, KeyExpansion(pwBytes));
173  key = key.concat(key.slice(0, nBytes-16));  // key is now 16/24/32 bytes long
174
175  // initialise counter block (NIST SP800-38A §B.2): millisecond time-stamp for nonce in 1st 8 bytes,
176  // block counter in 2nd 8 bytes
177  var blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
178  var counterBlock = new Array(blockSize);  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
179  var nonce = (new Date()).getTime();  // milliseconds since 1-Jan-1970
180
181  // encode nonce in two stages to cater for JavaScript 32-bit limit on bitwise ops
182  for (var i=0; i<4; i++) counterBlock[i] = (nonce >>> i*8) & 0xff;
183  for (var i=0; i<4; i++) counterBlock[i+4] = (nonce/0x100000000 >>> i*8) & 0xff;
184
185  // generate key schedule - an expansion of the key into distinct Key Rounds for each round
186  var keySchedule = KeyExpansion(key);
187
188  var blockCount = Math.ceil(plaintext.length/blockSize);
189  var ciphertext = new Array(blockCount);  // ciphertext as array of strings
190
191  for (var b=0; b<blockCount; b++) {
192    // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
193    // again done in two stages for 32-bit ops
194    for (var c=0; c<4; c++) counterBlock[15-c] = (b >>> c*8) & 0xff;
195    for (var c=0; c<4; c++) counterBlock[15-c-4] = (b/0x100000000 >>> c*8)
196
197    var cipherCntr = Cipher(counterBlock, keySchedule);  // -- encrypt counter block --
198
199    // calculate length of final block:
200    var blockLength = b<blockCount-1 ? blockSize : (plaintext.length-1)%blockSize+1;
201
202    var ct = '';
203    for (var i=0; i<blockLength; i++) {  // -- xor plaintext with ciphered counter byte-by-byte --
204      var plaintextByte = plaintext.charCodeAt(b*blockSize+i);
205      var cipherByte = plaintextByte ^ cipherCntr[i];
206      ct += String.fromCharCode(cipherByte);
207    }
208    // ct is now ciphertext for this block
209
210    ciphertext[b] = escCtrlChars(ct);  // escape troublesome characters in ciphertext
211  }
212
213  // convert the nonce to a string to go on the front of the ciphertext
214  var ctrTxt = '';
215  for (var i=0; i<8; i++) ctrTxt += String.fromCharCode(counterBlock[i]);
216  ctrTxt = escCtrlChars(ctrTxt);
217
218  // use '-' to separate blocks, use Array.join to concatenate arrays of strings for efficiency
219  return ctrTxt + '-' + ciphertext.join('-');
220}
221
222
223/*
224 * Use AES to decrypt 'ciphertext' with 'password' using 'nBits' key, in Counter mode of operation
225 *
226 *   for each block
227 *   - outputblock = cipher(counter, key)
228 *   - cipherblock = plaintext xor outputblock
229 */
230function AESDecryptCtr(ciphertext, password, nBits) {
231  if (!(nBits==128 || nBits==192 || nBits==256)) return '';  // standard allows 128/192/256 bit keys
232
233  var nBytes = nBits/8;  // no bytes in key
234  var pwBytes = new Array(nBytes);
235  for (var i=0; i<nBytes; i++) pwBytes[i] = password.charCodeAt(i) & 0xff;
236  var pwKeySchedule = KeyExpansion(pwBytes);
237  var key = Cipher(pwBytes, pwKeySchedule);
238  key = key.concat(key.slice(0, nBytes-16));  // key is now 16/24/32 bytes long
239
240  var keySchedule = KeyExpansion(key);
241
242  ciphertext = ciphertext.split('-');  // split ciphertext into array of block-length strings
243
244  // recover nonce from 1st element of ciphertext
245  var blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
246  var counterBlock = new Array(blockSize);
247  var ctrTxt = unescCtrlChars(ciphertext[0]);
248  for (var i=0; i<8; i++) counterBlock[i] = ctrTxt.charCodeAt(i);
249
250  var plaintext = new Array(ciphertext.length-1);
251
252  for (var b=1; b<ciphertext.length; b++) {
253    // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
254    for (var c=0; c<4; c++) counterBlock[15-c] = ((b-1) >>> c*8) & 0xff;
255    for (var c=0; c<4; c++) counterBlock[15-c-4] = ((b/0x100000000-1) >>> c*8) & 0xff;
256
257    var cipherCntr = Cipher(counterBlock, keySchedule);  // encrypt counter block
258
259    ciphertext[b] = unescCtrlChars(ciphertext[b]);
260
261    var pt = '';
262    for (var i=0; i<ciphertext[b].length; i++) {
263      // -- xor plaintext with ciphered counter byte-by-byte --
264      var ciphertextByte = ciphertext[b].charCodeAt(i);
265      var plaintextByte = ciphertextByte ^ cipherCntr[i];
266      pt += String.fromCharCode(plaintextByte);
267    }
268    // pt is now plaintext for this block
269
270    plaintext[b-1] = pt;  // b-1 'cos no initial nonce block in plaintext
271  }
272
273  return plaintext.join('');
274}
275
276/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
277
278function escCtrlChars(str) {  // escape control chars which might cause problems handling ciphertext
279  return str.replace(/[\0\t\n\v\f\r\xa0'"!-]/g, function(c) { return '!' + c.charCodeAt(0) + '!'; });
280}  // \xa0 to cater for bug in Firefox; include '-' to leave it free for use as a block marker
281
282function unescCtrlChars(str) {  // unescape potentially problematic control characters
283  return str.replace(/!\d\d?\d?!/g, function(c) { return String.fromCharCode(c.slice(1,-1)); });
284}
285/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
286
287/*
288 * if escCtrlChars()/unescCtrlChars() still gives problems, use encodeBase64()/decodeBase64() instead
289 */
290var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
291
292function encodeBase64(str) {  // http://tools.ietf.org/html/rfc4648
293   var o1, o2, o3, h1, h2, h3, h4, bits, i=0, enc='';
294
295   str = encodeUTF8(str);  // encode multi-byte chars into UTF-8 for byte-array
296
297   do {  // pack three octets into four hexets
298      o1 = str.charCodeAt(i++);
299      o2 = str.charCodeAt(i++);
300      o3 = str.charCodeAt(i++);
301
302      bits = o1<<16 | o2<<8 | o3;
303
304      h1 = bits>>18 & 0x3f;
305      h2 = bits>>12 & 0x3f;
306      h3 = bits>>6 & 0x3f;
307      h4 = bits & 0x3f;
308
309      // end of string? index to '=' in b64
310      if (isNaN(o3)) h4 = 64;
311      if (isNaN(o2)) h3 = 64;
312
313      // use hexets to index into b64, and append result to encoded string
314      enc += b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
315   } while (i < str.length);
316
317   return enc;
318}
319
320function decodeBase64(str) {
321   var o1, o2, o3, h1, h2, h3, h4, bits, i=0, enc='';
322
323   do {  // unpack four hexets into three octets using index points in b64
324      h1 = b64.indexOf(str.charAt(i++));
325      h2 = b64.indexOf(str.charAt(i++));
326      h3 = b64.indexOf(str.charAt(i++));
327      h4 = b64.indexOf(str.charAt(i++));
328
329      bits = h1<<18 | h2<<12 | h3<<6 | h4;
330
331      o1 = bits>>16 & 0xff;
332      o2 = bits>>8 & 0xff;
333      o3 = bits & 0xff;
334
335      if (h3 == 64)      enc += String.fromCharCode(o1);
336      else if (h4 == 64) enc += String.fromCharCode(o1, o2);
337      else               enc += String.fromCharCode(o1, o2, o3);
338   } while (i < str.length);
339
340   return decodeUTF8(enc);  // decode UTF-8 byte-array back to Unicode
341}
342
343function encodeUTF8(str) {  // encode multi-byte string into utf-8 multiple single-byte characters
344  str = str.replace(
345      /[\u0080-\u07ff]/g,  // U+0080 - U+07FF = 2-byte chars
346      function(c) {
347        var cc = c.charCodeAt(0);
348        return String.fromCharCode(0xc0 | cc>>6, 0x80 | cc&0x3f); }
349    );
350  str = str.replace(
351      /[\u0800-\uffff]/g,  // U+0800 - U+FFFF = 3-byte chars
352      function(c) {
353        var cc = c.charCodeAt(0);
354        return String.fromCharCode(0xe0 | cc>>12, 0x80 | cc>>6&0x3F, 0x80 | cc&0x3f); }
355    );
356  return str;
357}
358
359function decodeUTF8(str) {  // decode utf-8 encoded string back into multi-byte characters
360  str = str.replace(
361      /[\u00c0-\u00df][\u0080-\u00bf]/g,                 // 2-byte chars
362      function(c) {
363        var cc = (c.charCodeAt(0)&0x1f)<<6 | c.charCodeAt(1)&0x3f;
364        return String.fromCharCode(cc); }
365    );
366  str = str.replace(
367      /[\u00e0-\u00ef][\u0080-\u00bf][\u0080-\u00bf]/g,  // 3-byte chars
368      function(c) {
369        var cc = (c.charCodeAt(0)&0x0f)<<12 | (c.charCodeAt(1)&0x3f<<6) | c.charCodeAt(2)&0x3f;
370        return String.fromCharCode(cc); }
371    );
372  return str;
373}
374
375
376function byteArrayToHexStr(b) {  // convert byte array to hex string for displaying test vectors
377  var s = '';
378  for (var i=0; i<b.length; i++) s += b[i].toString(16) + ' ';
379  return s;
380}
381
382/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
383
384
385var plainText = "ROMEO: But, soft! what light through yonder window breaks?\n\
386It is the east, and Juliet is the sun.\n\
387Arise, fair sun, and kill the envious moon,\n\
388Who is already sick and pale with grief,\n\
389That thou her maid art far more fair than she:\n\
390Be not her maid, since she is envious;\n\
391Her vestal livery is but sick and green\n\
392And none but fools do wear it; cast it off.\n\
393It is my lady, O, it is my love!\n\
394O, that she knew she were!\n\
395She speaks yet she says nothing: what of that?\n\
396Her eye discourses; I will answer it.\n\
397I am too bold, 'tis not to me she speaks:\n\
398Two of the fairest stars in all the heaven,\n\
399Having some business, do entreat her eyes\n\
400To twinkle in their spheres till they return.\n\
401What if her eyes were there, they in her head?\n\
402The brightness of her cheek would shame those stars,\n\
403As daylight doth a lamp; her eyes in heaven\n\
404Would through the airy region stream so bright\n\
405That birds would sing and think it were not night.\n\
406See, how she leans her cheek upon her hand!\n\
407O, that I were a glove upon that hand,\n\
408That I might touch that cheek!\n\
409JULIET: Ay me!\n\
410ROMEO: She speaks:\n\
411O, speak again, bright angel! for thou art\n\
412As glorious to this night, being o'er my head\n\
413As is a winged messenger of heaven\n\
414Unto the white-upturned wondering eyes\n\
415Of mortals that fall back to gaze on him\n\
416When he bestrides the lazy-pacing clouds\n\
417And sails upon the bosom of the air.";
418
419var password = "O Romeo, Romeo! wherefore art thou Romeo?";
420
421var cipherText = AESEncryptCtr(plainText, password, 256);
422var decryptedText = AESDecryptCtr(cipherText, password, 256);
423