/** @fileOverview Javascript cryptography implementation.
 *
 * Crush to remove comments, shorten variable names and
 * generally reduce transmission size.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

"use strict";
/*jslint indent: 2, bitwise: false, nomen: false, plusplus: false, white: false, regexp: false */
/*global document, window, escape, unescape */

/** @namespace The Stanford Javascript Crypto Library, top-level namespace. */
var sjcl = {
  /** @namespace Symmetric ciphers. */
  cipher: {},

  /** @namespace Hash functions.  Right now only SHA256 is implemented. */
  hash: {},
  
  /** @namespace Block cipher modes of operation. */
  mode: {},

  /** @namespace Miscellaneous.  HMAC and PBKDF2. */
  misc: {},
  
  /**
   * @namespace Bit array encoders and decoders.
   *
   * @description
   * The members of this namespace are functions which translate between
   * SJCL's bitArrays and other objects (usually strings).  Because it
   * isn't always clear which direction is encoding and which is decoding,
   * the method names are "fromBits" and "toBits".
   */
  codec: {},
  
  /** @namespace Exceptions. */
  exception: {
    /** @class Ciphertext is corrupt. */
    corrupt: function(message) {
      this.toString = function() { return "CORRUPT: "+this.message; };
      this.message = message;
    },
    
    /** @class Invalid parameter. */
    invalid: function(message) {
      this.toString = function() { return "INVALID: "+this.message; };
      this.message = message;
    },
    
    /** @class Bug or missing feature in SJCL. */
    bug: function(message) {
      this.toString = function() { return "BUG: "+this.message; };
      this.message = message;
    }
  }
};
/** @fileOverview Low-level AES implementation.
 *
 * This file contains a low-level implementation of AES, optimized for
 * size and for efficiency on several browsers.  It is based on
 * OpenSSL's aes_core.c, a public-domain implementation by Vincent
 * Rijmen, Antoon Bosselaers and Paulo Barreto.
 *
 * An older version of this implementation is available in the public
 * domain, but this one is (c) Emily Stark, Mike Hamburg, Dan Boneh,
 * Stanford University 2008-2010 and BSD-licensed for liability
 * reasons.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/**
 * Schedule out an AES key for both encryption and decryption.  This
 * is a low-level class.  Use a cipher mode to do bulk encryption.
 *
 * @constructor
 * @param {Array} key The key as an array of 4, 6 or 8 words.
 *
 * @class Advanced Encryption Standard (low-level interface)
 */
sjcl.cipher.aes = function (key) {
  if (!this._tables[0][0][0]) {
    this._precompute();
  }
  
  var i, j, tmp,
    encKey, decKey,
    sbox = this._tables[0][4], decTable = this._tables[1],
    keyLen = key.length, rcon = 1;
  
  if (keyLen !== 4 && keyLen !== 6 && keyLen !== 8) {
    throw new sjcl.exception.invalid("invalid aes key size");
  }
  
  this._key = [encKey = key.slice(0), decKey = []];
  
  // schedule encryption keys
  for (i = keyLen; i < 4 * keyLen + 28; i++) {
    tmp = encKey[i-1];
    
    // apply sbox
    if (i%keyLen === 0 || (keyLen === 8 && i%keyLen === 4)) {
      tmp = sbox[tmp>>>24]<<24 ^ sbox[tmp>>16&255]<<16 ^ sbox[tmp>>8&255]<<8 ^ sbox[tmp&255];
      
      // shift rows and add rcon
      if (i%keyLen === 0) {
        tmp = tmp<<8 ^ tmp>>>24 ^ rcon<<24;
        rcon = rcon<<1 ^ (rcon>>7)*283;
      }
    }
    
    encKey[i] = encKey[i-keyLen] ^ tmp;
  }
  
  // schedule decryption keys
  for (j = 0; i; j++, i--) {
    tmp = encKey[j&3 ? i : i - 4];
    if (i<=4 || j<4) {
      decKey[j] = tmp;
    } else {
      decKey[j] = decTable[0][sbox[tmp>>>24      ]] ^
                  decTable[1][sbox[tmp>>16  & 255]] ^
                  decTable[2][sbox[tmp>>8   & 255]] ^
                  decTable[3][sbox[tmp      & 255]];
    }
  }
};

sjcl.cipher.aes.prototype = {
  // public
  /* Something like this might appear here eventually
  name: "AES",
  blockSize: 4,
  keySizes: [4,6,8],
  */
  
  /**
   * Encrypt an array of 4 big-endian words.
   * @param {Array} data The plaintext.
   * @return {Array} The ciphertext.
   */
  encrypt:function (data) { return this._crypt(data,0); },
  
  /**
   * Decrypt an array of 4 big-endian words.
   * @param {Array} data The ciphertext.
   * @return {Array} The plaintext.
   */
  decrypt:function (data) { return this._crypt(data,1); },
  
  /**
   * The expanded S-box and inverse S-box tables.  These will be computed
   * on the client so that we don't have to send them down the wire.
   *
   * There are two tables, _tables[0] is for encryption and
   * _tables[1] is for decryption.
   *
   * The first 4 sub-tables are the expanded S-box with MixColumns.  The
   * last (_tables[01][4]) is the S-box itself.
   *
   * @private
   */
  _tables: [[[],[],[],[],[]],[[],[],[],[],[]]],

  /**
   * Expand the S-box tables.
   *
   * @private
   */
  _precompute: function () {
   var encTable = this._tables[0], decTable = this._tables[1],
       sbox = encTable[4], sboxInv = decTable[4],
       i, x, xInv, d=[], th=[], x2, x4, x8, s, tEnc, tDec;

    // Compute double and third tables
   for (i = 0; i < 256; i++) {
     th[( d[i] = i<<1 ^ (i>>7)*283 )^i]=i;
   }
   
   for (x = xInv = 0; !sbox[x]; x ^= x2 || 1, xInv = th[xInv] || 1) {
     // Compute sbox
     s = xInv ^ xInv<<1 ^ xInv<<2 ^ xInv<<3 ^ xInv<<4;
     s = s>>8 ^ s&255 ^ 99;
     sbox[x] = s;
     sboxInv[s] = x;
     
     // Compute MixColumns
     x8 = d[x4 = d[x2 = d[x]]];
     tDec = x8*0x1010101 ^ x4*0x10001 ^ x2*0x101 ^ x*0x1010100;
     tEnc = d[s]*0x101 ^ s*0x1010100;
     
     for (i = 0; i < 4; i++) {
       encTable[i][x] = tEnc = tEnc<<24 ^ tEnc>>>8;
       decTable[i][s] = tDec = tDec<<24 ^ tDec>>>8;
     }
   }
   
   // Compactify.  Considerable speedup on Firefox.
   for (i = 0; i < 5; i++) {
     encTable[i] = encTable[i].slice(0);
     decTable[i] = decTable[i].slice(0);
   }
  },
  
  /**
   * Encryption and decryption core.
   * @param {Array} input Four words to be encrypted or decrypted.
   * @param dir The direction, 0 for encrypt and 1 for decrypt.
   * @return {Array} The four encrypted or decrypted words.
   * @private
   */
  _crypt:function (input, dir) {
    if (input.length !== 4) {
      throw new sjcl.exception.invalid("invalid aes block size");
    }
    
    var key = this._key[dir],
        // state variables a,b,c,d are loaded with pre-whitened data
        a = input[0]           ^ key[0],
        b = input[dir ? 3 : 1] ^ key[1],
        c = input[2]           ^ key[2],
        d = input[dir ? 1 : 3] ^ key[3],
        a2, b2, c2,
        
        nInnerRounds = key.length/4 - 2,
        i,
        kIndex = 4,
        out = [0,0,0,0],
        table = this._tables[dir],
        
        // load up the tables
        t0    = table[0],
        t1    = table[1],
        t2    = table[2],
        t3    = table[3],
        sbox  = table[4];
 
    // Inner rounds.  Cribbed from OpenSSL.
    for (i = 0; i < nInnerRounds; i++) {
      a2 = t0[a>>>24] ^ t1[b>>16 & 255] ^ t2[c>>8 & 255] ^ t3[d & 255] ^ key[kIndex];
      b2 = t0[b>>>24] ^ t1[c>>16 & 255] ^ t2[d>>8 & 255] ^ t3[a & 255] ^ key[kIndex + 1];
      c2 = t0[c>>>24] ^ t1[d>>16 & 255] ^ t2[a>>8 & 255] ^ t3[b & 255] ^ key[kIndex + 2];
      d  = t0[d>>>24] ^ t1[a>>16 & 255] ^ t2[b>>8 & 255] ^ t3[c & 255] ^ key[kIndex + 3];
      kIndex += 4;
      a=a2; b=b2; c=c2;
    }
        
    // Last round.
    for (i = 0; i < 4; i++) {
      out[dir ? 3&-i : i] =
        sbox[a>>>24      ]<<24 ^ 
        sbox[b>>16  & 255]<<16 ^
        sbox[c>>8   & 255]<<8  ^
        sbox[d      & 255]     ^
        key[kIndex++];
      a2=a; a=b; b=c; c=d; d=a2;
    }
    
    return out;
  }
};

/** @fileOverview Arrays of bits, encoded as arrays of Numbers.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** @namespace Arrays of bits, encoded as arrays of Numbers.
 *
 * @description
 * <p>
 * These objects are the currency accepted by SJCL's crypto functions.
 * </p>
 *
 * <p>
 * Most of our crypto primitives operate on arrays of 4-byte words internally,
 * but many of them can take arguments that are not a multiple of 4 bytes.
 * This library encodes arrays of bits (whose size need not be a multiple of 8
 * bits) as arrays of 32-bit words.  The bits are packed, big-endian, into an
 * array of words, 32 bits at a time.  Since the words are double-precision
 * floating point numbers, they fit some extra data.  We use this (in a private,
 * possibly-changing manner) to encode the number of bits actually  present
 * in the last word of the array.
 * </p>
 *
 * <p>
 * Because bitwise ops clear this out-of-band data, these arrays can be passed
 * to ciphers like AES which want arrays of words.
 * </p>
 */
sjcl.bitArray = {
  /**
   * Array slices in units of bits.
   * @param {bitArray a} The array to slice.
   * @param {Number} bstart The offset to the start of the slice, in bits.
   * @param {Number} bend The offset to the end of the slice, in bits.  If this is undefined,
   * slice until the end of the array.
   * @return {bitArray} The requested slice.
   */
  bitSlice: function (a, bstart, bend) {
    a = sjcl.bitArray._shiftRight(a.slice(bstart/32), 32 - (bstart & 31)).slice(1);
    return (bend === undefined) ? a : sjcl.bitArray.clamp(a, bend-bstart);
  },

  /**
   * Concatenate two bit arrays.
   * @param {bitArray} a1 The first array.
   * @param {bitArray} a2 The second array.
   * @return {bitArray} The concatenation of a1 and a2.
   */
  concat: function (a1, a2) {
    if (a1.length === 0 || a2.length === 0) {
      return a1.concat(a2);
    }
    
    var out, i, last = a1[a1.length-1], shift = sjcl.bitArray.getPartial(last);
    if (shift === 32) {
      return a1.concat(a2);
    } else {
      return sjcl.bitArray._shiftRight(a2, shift, last|0, a1.slice(0,a1.length-1));
    }
  },

  /**
   * Find the length of an array of bits.
   * @param {bitArray} a The array.
   * @return {Number} The length of a, in bits.
   */
  bitLength: function (a) {
    var l = a.length, x;
    if (l === 0) { return 0; }
    x = a[l - 1];
    return (l-1) * 32 + sjcl.bitArray.getPartial(x);
  },

  /**
   * Truncate an array.
   * @param {bitArray} a The array.
   * @param {Number} len The length to truncate to, in bits.
   * @return {bitArray} A new array, truncated to len bits.
   */
  clamp: function (a, len) {
    if (a.length * 32 < len) { return a; }
    a = a.slice(0, Math.ceil(len / 32));
    var l = a.length;
    len = len & 31;
    if (l > 0 && len) {
      a[l-1] = sjcl.bitArray.partial(len, a[l-1] & 0x80000000 >> (len-1), 1);
    }
    return a;
  },

  /**
   * Make a partial word for a bit array.
   * @param {Number} len The number of bits in the word.
   * @param {Number} x The bits.
   * @param {Number} [0] _end Pass 1 if x has already been shifted to the high side.
   * @return {Number} The partial word.
   */
  partial: function (len, x, _end) {
    if (len === 32) { return x; }
    return (_end ? x|0 : x << (32-len)) + len * 0x10000000000;
  },

  /**
   * Get the number of bits used by a partial word.
   * @param {Number} x The partial word.
   * @return {Number} The number of bits used by the partial word.
   */
  getPartial: function (x) {
    return Math.round(x/0x10000000000) || 32;
  },

  /**
   * Compare two arrays for equality in a predictable amount of time.
   * @param {bitArray} a The first array.
   * @param {bitArray} b The second array.
   * @return {boolean} true if a == b; false otherwise.
   */
  equal: function (a, b) {
    if (sjcl.bitArray.bitLength(a) !== sjcl.bitArray.bitLength(b)) {
      return false;
    }
    var x = 0, i;
    for (i=0; i<a.length; i++) {
      x |= a[i]^b[i];
    }
    return (x === 0);
  },

  /** Shift an array right.
   * @param {bitArray} a The array to shift.
   * @param {Number} shift The number of bits to shift.
   * @param {Number} [carry=0] A byte to carry in
   * @param {bitArray} [out=[]] An array to prepend to the output.
   * @private
   */
  _shiftRight: function (a, shift, carry, out) {
    var i, last2=0, shift2;
    if (out === undefined) { out = []; }
    
    for (; shift >= 32; shift -= 32) {
      out.push(carry);
      carry = 0;
    }
    if (shift === 0) {
      return out.concat(a);
    }
    
    for (i=0; i<a.length; i++) {
      out.push(carry | a[i]>>>shift);
      carry = a[i] << (32-shift);
    }
    last2 = a.length ? a[a.length-1] : 0;
    shift2 = sjcl.bitArray.getPartial(last2);
    out.push(sjcl.bitArray.partial(shift+shift2 & 31, (shift + shift2 > 32) ? carry : out.pop(),1));
    return out;
  },
  
  /** xor a block of 4 words together.
   * @private
   */
  _xor4: function(x,y) {
    return [x[0]^y[0],x[1]^y[1],x[2]^y[2],x[3]^y[3]];
  }
};
/** @fileOverview Bit array codec implementations.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */
 
/** @namespace UTF-8 strings */
sjcl.codec.utf8String = {
  /** Convert from a bitArray to a UTF-8 string. */
  fromBits: function (arr) {
    var out = "", bl = sjcl.bitArray.bitLength(arr), i, tmp;
    for (i=0; i<bl/8; i++) {
      if ((i&3) === 0) {
        tmp = arr[i/4];
      }
      out += String.fromCharCode(tmp >>> 24);
      tmp <<= 8;
    }
    return decodeURIComponent(escape(out));
  },
  
  /** Convert from a UTF-8 string to a bitArray. */
  toBits: function (str) {
    str = unescape(encodeURIComponent(str));
    var out = [], i, tmp=0;
    for (i=0; i<str.length; i++) {
      tmp = tmp << 8 | str.charCodeAt(i);
      if ((i&3) === 3) {
        out.push(tmp);
        tmp = 0;
      }
    }
    if (i&3) {
      out.push(sjcl.bitArray.partial(8*(i&3), tmp));
    }
    return out;
  }
};
/** @fileOverview Bit array codec implementations.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** @namespace Hexadecimal */
sjcl.codec.hex = {
  /** Convert from a bitArray to a hex string. */
  fromBits: function (arr) {
    var out = "", i, x;
    for (i=0; i<arr.length; i++) {
      out += ((arr[i]|0)+0xF00000000000).toString(16).substr(4);
    }
    return out.substr(0, sjcl.bitArray.bitLength(arr)/4);//.replace(/(.{8})/g, "$1 ");
  },
  /** Convert from a hex string to a bitArray. */
  toBits: function (str) {
    var i, out=[], len;
    str = str.replace(/\s|0x/g, "");
    len = str.length;
    str = str + "00000000";
    for (i=0; i<str.length; i+=8) {
      out.push(parseInt(str.substr(i,8),16)^0);
    }
    return sjcl.bitArray.clamp(out, len*4);
  }
};

/** @fileOverview Bit array codec implementations.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** @namespace Base64 encoding/decoding */
sjcl.codec.base64 = {
  /** The base64 alphabet.
   * @private
   */
  _chars: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
  
  /** Convert from a bitArray to a base64 string. */
  fromBits: function (arr, _noEquals) {
    var out = "", i, bits=0, c = sjcl.codec.base64._chars, ta=0, bl = sjcl.bitArray.bitLength(arr);
    for (i=0; out.length * 6 < bl; ) {
      out += c.charAt((ta ^ arr[i]>>>bits) >>> 26);
      if (bits < 6) {
        ta = arr[i] << (6-bits);
        bits += 26;
        i++;
      } else {
        ta <<= 6;
        bits -= 6;
      }
    }
    while ((out.length & 3) && !_noEquals) { out += "="; }
    return out;
  },
  
  /** Convert from a base64 string to a bitArray */
  toBits: function(str) {
    str = str.replace(/\s|=/g,'');
    var out = [], i, bits=0, c = sjcl.codec.base64._chars, ta=0, x;
    for (i=0; i<str.length; i++) {
      x = c.indexOf(str.charAt(i));
      if (x < 0) {
        throw new sjcl.exception.invalid("this isn't base64!");
      }
      if (bits > 26) {
        bits -= 26;
        out.push(ta ^ x>>>bits);
        ta  = x << (32-bits);
      } else {
        bits += 6;
        ta ^= x << (32-bits);
      }
    }
    if (bits&56) {
      out.push(sjcl.bitArray.partial(bits&56, ta, 1));
    }
    return out;
  }
};
/** @fileOverview Bit array codec implementations.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** @namespace Arrays of bytes */
sjcl.codec.bytes = {
  /** Convert from a bitArray to an array of bytes. */
  fromBits: function (arr) {
    var out = [], bl = sjcl.bitArray.bitLength(arr), i, tmp;
    for (i=0; i<bl/8; i++) {
      if ((i&3) === 0) {
        tmp = arr[i/4];
      }
      out.push(tmp >>> 24);
      tmp <<= 8;
    }
    return out;
  },
  /** Convert from an array of bytes to a bitArray. */
  toBits: function (bytes) {
    var out = [], i, tmp=0;
    for (i=0; i<bytes.length; i++) {
      tmp = tmp << 8 | bytes[i];
      if ((i&3) === 3) {
        out.push(tmp);
        tmp = 0;
      }
    }
    if (i&3) {
      out.push(sjcl.bitArray.partial(8*(i&3), tmp));
    }
    return out;
  }
};
/** @fileOverview Javascript SHA-256 implementation.
 *
 * An older version of this implementation is available in the public
 * domain, but this one is (c) Emily Stark, Mike Hamburg, Dan Boneh,
 * Stanford University 2008-2010 and BSD-licensed for liability
 * reasons.
 *
 * Special thanks to Aldo Cortesi for pointing out several bugs in
 * this code.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/**
 * Context for a SHA-256 operation in progress.
 * @constructor
 * @class Secure Hash Algorithm, 256 bits.
 */
sjcl.hash.sha256 = function (hash) {
  if (!this._key[0]) { this._precompute(); }
  if (hash) {
    this._h = hash._h.slice(0);
    this._buffer = hash._buffer.slice(0);
    this._length = hash._length;
  } else {
    this.reset();
  }
};

/**
 * Hash a string or an array of words.
 * @static
 * @param {bitArray|String} data the data to hash.
 * @return {bitArray} The hash value, an array of 16 big-endian words.
 */
sjcl.hash.sha256.hash = function (data) {
  return (new sjcl.hash.sha256()).update(data).finalize();
};

sjcl.hash.sha256.prototype = {
  /**
   * The hash's block size, in bits.
   * @constant
   */
  blockSize: 512,
   
  /**
   * Reset the hash state.
   * @return this
   */
  reset:function () {
    this._h = this._init.slice(0);
    this._buffer = [];
    this._length = 0;
    return this;
  },
  
  /**
   * Input several words to the hash.
   * @param {bitArray|String} data the data to hash.
   * @return this
   */
  update: function (data) {
    if (typeof data === "string") {
      data = sjcl.codec.utf8String.toBits(data);
    }
    var i, b = this._buffer = sjcl.bitArray.concat(this._buffer, data),
        ol = this._length,
        nl = this._length = ol + sjcl.bitArray.bitLength(data);
    for (i = 512+ol & -512; i <= nl; i+= 512) {
      this._block(b.splice(0,16));
    }
    return this;
  },
  
  /**
   * Complete hashing and output the hash value.
   * @return {bitArray} The hash value, an array of 16 big-endian words.
   */
  finalize:function () {
    var i, b = this._buffer, h = this._h;

    // Round out and push the buffer
    b = sjcl.bitArray.concat(b, [sjcl.bitArray.partial(1,1)]);
    
    // Round out the buffer to a multiple of 16 words, less the 2 length words.
    for (i = b.length + 2; i & 15; i++) {
      b.push(0);
    }
    
    // append the length
    b.push(Math.floor(this._length / 0x100000000));
    b.push(this._length | 0);

    while (b.length) {
      this._block(b.splice(0,16));
    }

    this.reset();
    return h;
  },

  /**
   * The SHA-256 initialization vector, to be precomputed.
   * @private
   */
  _init:[],
  /*
  _init:[0x6a09e667,0xbb67ae85,0x3c6ef372,0xa54ff53a,0x510e527f,0x9b05688c,0x1f83d9ab,0x5be0cd19],
  */
  
  /**
   * The SHA-256 hash key, to be precomputed.
   * @private
   */
  _key:[],
  /*
  _key:
    [0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
     0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
     0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
     0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
     0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
     0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
     0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
     0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2],
  */


  /**
   * Function to precompute _init and _key.
   * @private
   */
  _precompute: function () {
    var i = 0, prime = 2, factor;

    function frac(x) { return (x-Math.floor(x)) * 0x100000000 | 0; }

    outer: for (; i<64; prime++) {
      for (factor=2; factor*factor <= prime; factor++) {
        if (prime % factor === 0) {
          // not a prime
          continue outer;
        }
      }
      
      if (i<8) {
        this._init[i] = frac(Math.pow(prime, 1/2));
      }
      this._key[i] = frac(Math.pow(prime, 1/3));
      i++;
    }
  },
  
  /**
   * Perform one cycle of SHA-256.
   * @param {bitArray} words one block of words.
   * @private
   */
  _block:function (words) {  
    var i, tmp, a, b,
      w = words.slice(0),
      h = this._h,
      k = this._key,
      h0 = h[0], h1 = h[1], h2 = h[2], h3 = h[3],
      h4 = h[4], h5 = h[5], h6 = h[6], h7 = h[7];

    /* Rationale for placement of |0 :
     * If a value can overflow is original 32 bits by a factor of more than a few
     * million (2^23 ish), there is a possibility that it might overflow the
     * 53-bit mantissa and lose precision.
     *
     * To avoid this, we clamp back to 32 bits by |'ing with 0 on any value that
     * propagates around the loop, and on the hash state h[].  I don't believe
     * that the clamps on h4 and on h0 are strictly necessary, but it's close
     * (for h4 anyway), and better safe than sorry.
     *
     * The clamps on h[] are necessary for the output to be correct even in the
     * common case and for short inputs.
     */
    for (i=0; i<64; i++) {
      // load up the input word for this round
      if (i<16) {
        tmp = w[i];
      } else {
        a   = w[(i+1 ) & 15];
        b   = w[(i+14) & 15];
        tmp = w[i&15] = ((a>>>7  ^ a>>>18 ^ a>>>3  ^ a<<25 ^ a<<14) + 
                         (b>>>17 ^ b>>>19 ^ b>>>10 ^ b<<15 ^ b<<13) +
                         w[i&15] + w[(i+9) & 15]) | 0;
      }
      
      tmp = (tmp + h7 + (h4>>>6 ^ h4>>>11 ^ h4>>>25 ^ h4<<26 ^ h4<<21 ^ h4<<7) +  (h6 ^ h4&(h5^h6)) + k[i]); // | 0;
      
      // shift register
      h7 = h6; h6 = h5; h5 = h4;
      h4 = h3 + tmp | 0;
      h3 = h2; h2 = h1; h1 = h0;

      h0 = (tmp +  ((h1&h2) ^ (h3&(h1^h2))) + (h1>>>2 ^ h1>>>13 ^ h1>>>22 ^ h1<<30 ^ h1<<19 ^ h1<<10)) | 0;
    }

    h[0] = h[0]+h0 | 0;
    h[1] = h[1]+h1 | 0;
    h[2] = h[2]+h2 | 0;
    h[3] = h[3]+h3 | 0;
    h[4] = h[4]+h4 | 0;
    h[5] = h[5]+h5 | 0;
    h[6] = h[6]+h6 | 0;
    h[7] = h[7]+h7 | 0;
  }
};


/** @fileOverview CCM mode implementation.
 *
 * Special thanks to Roy Nicholson for pointing out a bug in our
 * implementation.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** @namespace CTR mode with CBC MAC. */
sjcl.mode.ccm = {
  /** The name of the mode.
   * @constant
   */
  name: "ccm",
  
  /** Encrypt in CCM mode.
   * @static
   * @param {Object} prf The pseudorandom function.  It must have a block size of 16 bytes.
   * @param {bitArray} plaintext The plaintext data.
   * @param {bitArray} iv The initialization value.
   * @param {bitArray} [adata=[]] The authenticated data.
   * @param {Number} [tlen=64] the desired tag length, in bits.
   * @return {bitArray} The encrypted data, an array of bytes.
   */
  encrypt: function(prf, plaintext, iv, adata, tlen) {
    var L, i, out = plaintext.slice(0), tag, w=sjcl.bitArray, ivl = w.bitLength(iv) / 8, ol = w.bitLength(out) / 8;
    tlen = tlen || 64;
    adata = adata || [];
    
    if (ivl < 7) {
      throw new sjcl.exception.invalid("ccm: iv must be at least 7 bytes");
    }
    
    // compute the length of the length
    for (L=2; L<4 && ol >>> 8*L; L++) {}
    if (L < 15 - ivl) { L = 15-ivl; }
    iv = w.clamp(iv,8*(15-L));
    
    // compute the tag
    tag = sjcl.mode.ccm._computeTag(prf, plaintext, iv, adata, tlen, L);
    
    // encrypt
    out = sjcl.mode.ccm._ctrMode(prf, out, iv, tag, tlen, L);
    
    return w.concat(out.data, out.tag);
  },
  
  /** Decrypt in CCM mode.
   * @static
   * @param {Object} prf The pseudorandom function.  It must have a block size of 16 bytes.
   * @param {bitArray} ciphertext The ciphertext data.
   * @param {bitArray} iv The initialization value.
   * @param {bitArray} [[]] adata The authenticated data.
   * @param {Number} [64] tlen the desired tag length, in bits.
   * @return {bitArray} The decrypted data.
   */
  decrypt: function(prf, ciphertext, iv, adata, tlen) {
    tlen = tlen || 64;
    adata = adata || [];
    var L, i, 
        w=sjcl.bitArray,
        ivl = w.bitLength(iv) / 8,
        ol = w.bitLength(ciphertext), 
        out = w.clamp(ciphertext, ol - tlen),
        tag = w.bitSlice(ciphertext, ol - tlen), tag2;
    

    ol = (ol - tlen) / 8;
        
    if (ivl < 7) {
      throw new sjcl.exception.invalid("ccm: iv must be at least 7 bytes");
    }
    
    // compute the length of the length
    for (L=2; L<4 && ol >>> 8*L; L++) {}
    if (L < 15 - ivl) { L = 15-ivl; }
    iv = w.clamp(iv,8*(15-L));
    
    // decrypt
    out = sjcl.mode.ccm._ctrMode(prf, out, iv, tag, tlen, L);
    
    // check the tag
    tag2 = sjcl.mode.ccm._computeTag(prf, out.data, iv, adata, tlen, L);
    if (!w.equal(out.tag, tag2)) {
      throw new sjcl.exception.corrupt("ccm: tag doesn't match");
    }
    
    return out.data;
  },

  /* Compute the (unencrypted) authentication tag, according to the CCM specification
   * @param {Object} prf The pseudorandom function.
   * @param {bitArray} plaintext The plaintext data.
   * @param {bitArray} iv The initialization value.
   * @param {bitArray} adata The authenticated data.
   * @param {Number} tlen the desired tag length, in bits.
   * @return {bitArray} The tag, but not yet encrypted.
   * @private
   */
  _computeTag: function(prf, plaintext, iv, adata, tlen, L) {
    // compute B[0]
    var q, mac, field = 0, offset = 24, tmp, i, macData = [], w=sjcl.bitArray, xor = w._xor4;

    tlen /= 8;
  
    // check tag length and message length
    if (tlen % 2 || tlen < 4 || tlen > 16) {
      throw new sjcl.exception.invalid("ccm: invalid tag length");
    }
  
    if (adata.length > 0xFFFFFFFF || plaintext.length > 0xFFFFFFFF) {
      // I don't want to deal with extracting high words from doubles.
      throw new sjcl.exception.bug("ccm: can't deal with 4GiB or more data");
    }

    // mac the flags
    mac = [w.partial(8, (adata.length ? 1<<6 : 0) | (tlen-2) << 2 | L-1)];

    // mac the iv and length
    mac = w.concat(mac, iv);
    mac[3] |= w.bitLength(plaintext)/8;
    mac = prf.encrypt(mac);
    
  
    if (adata.length) {
      // mac the associated data.  start with its length...
      tmp = w.bitLength(adata)/8;
      if (tmp <= 0xFEFF) {
        macData = [w.partial(16, tmp)];
      } else if (tmp <= 0xFFFFFFFF) {
        macData = w.concat([w.partial(16,0xFFFE)], [tmp]);
      } // else ...
    
      // mac the data itself
      macData = w.concat(macData, adata);
      for (i=0; i<macData.length; i += 4) {
        mac = prf.encrypt(xor(mac, macData.slice(i,i+4).concat([0,0,0])));
      }
    }
  
    // mac the plaintext
    for (i=0; i<plaintext.length; i+=4) {
      mac = prf.encrypt(xor(mac, plaintext.slice(i,i+4).concat([0,0,0])));
    }

    return w.clamp(mac, tlen * 8);
  },

  /** CCM CTR mode.
   * Encrypt or decrypt data and tag with the prf in CCM-style CTR mode.
   * May mutate its arguments.
   * @param {Object} prf The PRF.
   * @param {bitArray} data The data to be encrypted or decrypted.
   * @param {bitArray} iv The initialization vector.
   * @param {bitArray} tag The authentication tag.
   * @param {Number} tlen The length of th etag, in bits.
   * @param {Number} L The CCM L value.
   * @return {Object} An object with data and tag, the en/decryption of data and tag values.
   * @private
   */
  _ctrMode: function(prf, data, iv, tag, tlen, L) {
    var enc, i, w=sjcl.bitArray, xor = w._xor4, ctr, b, l = data.length, bl=w.bitLength(data);

    // start the ctr
    ctr = w.concat([w.partial(8,L-1)],iv).concat([0,0,0]).slice(0,4);
    
    // en/decrypt the tag
    tag = w.bitSlice(xor(tag,prf.encrypt(ctr)), 0, tlen);
  
    // en/decrypt the data
    if (!l) { return {tag:tag, data:[]}; }
    
    for (i=0; i<l; i+=4) {
      ctr[3]++;
      enc = prf.encrypt(ctr);
      data[i]   ^= enc[0];
      data[i+1] ^= enc[1];
      data[i+2] ^= enc[2];
      data[i+3] ^= enc[3];
    }
    return { tag:tag, data:w.clamp(data,bl) };
  }
};
/** @fileOverview OCB 2.0 implementation
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** @namespace
 * Phil Rogaway's Offset CodeBook mode, version 2.0.
 * May be covered by US and international patents.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */
sjcl.mode.ocb2 = {
  /** The name of the mode.
   * @constant
   */
  name: "ocb2",
  
  /** Encrypt in OCB mode, version 2.0.
   * @param {Object} prp The block cipher.  It must have a block size of 16 bytes.
   * @param {bitArray} plaintext The plaintext data.
   * @param {bitArray} iv The initialization value.
   * @param {bitArray} [adata=[]] The authenticated data.
   * @param {Number} [tlen=64] the desired tag length, in bits.
   * @param [false] premac 1 if the authentication data is pre-macced with PMAC.
   * @return The encrypted data, an array of bytes.
   * @throws {sjcl.exception.invalid} if the IV isn't exactly 128 bits.
   */
  encrypt: function(prp, plaintext, iv, adata, tlen, premac) {
    if (sjcl.bitArray.bitLength(iv) !== 128) {
      throw new sjcl.exception.invalid("ocb iv must be 128 bits");
    }
    var i,
        times2 = sjcl.mode.ocb2._times2,
        w = sjcl.bitArray,
        xor = w._xor4,
        checksum = [0,0,0,0],
        delta = times2(prp.encrypt(iv)),
        bi, bl,
        output = [],
        pad;
        
    adata = adata || [];
    tlen  = tlen || 64;
  
    for (i=0; i+4 < plaintext.length; i+=4) {
      /* Encrypt a non-final block */
      bi = plaintext.slice(i,i+4);
      checksum = xor(checksum, bi);
      output = output.concat(xor(delta,prp.encrypt(xor(delta, bi))));
      delta = times2(delta);
    }
    
    /* Chop out the final block */
    bi = plaintext.slice(i);
    bl = w.bitLength(bi);
    pad = prp.encrypt(xor(delta,[0,0,0,bl]));
    bi = w.clamp(xor(bi.concat([0,0,0]),pad), bl);
    
    /* Checksum the final block, and finalize the checksum */
    checksum = xor(checksum,xor(bi.concat([0,0,0]),pad));
    checksum = prp.encrypt(xor(checksum,xor(delta,times2(delta))));
    
    /* MAC the header */
    if (adata.length) {
      checksum = xor(checksum, premac ? adata : sjcl.mode.ocb2.pmac(prp, adata));
    }
    
    return output.concat(w.concat(bi, w.clamp(checksum, tlen)));
  },
  
  /** Decrypt in OCB mode.
   * @param {Object} prp The block cipher.  It must have a block size of 16 bytes.
   * @param {bitArray} ciphertext The ciphertext data.
   * @param {bitArray} iv The initialization value.
   * @param {bitArray} [adata=[]] The authenticated data.
   * @param {Number} [tlen=64] the desired tag length, in bits.
   * @param {boolean} [premac=false] true if the authentication data is pre-macced with PMAC.
   * @return The decrypted data, an array of bytes.
   * @throws {sjcl.exception.invalid} if the IV isn't exactly 128 bits.
   * @throws {sjcl.exception.corrupt} if if the message is corrupt.
   */
  decrypt: function(prp, ciphertext, iv, adata, tlen, premac) {
    if (sjcl.bitArray.bitLength(iv) !== 128) {
      throw new sjcl.exception.invalid("ocb iv must be 128 bits");
    }
    tlen  = tlen || 64;
    var i,
        times2 = sjcl.mode.ocb2._times2,
        w = sjcl.bitArray,
        xor = w._xor4,
        checksum = [0,0,0,0],
        delta = times2(prp.encrypt(iv)),
        bi, bl,
        len = sjcl.bitArray.bitLength(ciphertext) - tlen,
        output = [],
        pad;
        
    adata = adata || [];
  
    for (i=0; i+4 < len/32; i+=4) {
      /* Decrypt a non-final block */
      bi = xor(delta, prp.decrypt(xor(delta, ciphertext.slice(i,i+4))));
      checksum = xor(checksum, bi);
      output = output.concat(bi);
      delta = times2(delta);
    }
    
    /* Chop out and decrypt the final block */
    bl = len-i*32;
    pad = prp.encrypt(xor(delta,[0,0,0,bl]));
    bi = xor(pad, w.clamp(ciphertext.slice(i),bl).concat([0,0,0]));
    
    /* Checksum the final block, and finalize the checksum */
    checksum = xor(checksum, bi);
    checksum = prp.encrypt(xor(checksum, xor(delta, times2(delta))));
    
    /* MAC the header */
    if (adata.length) {
      checksum = xor(checksum, premac ? adata : sjcl.mode.ocb2.pmac(prp, adata));
    }
    
    if (!w.equal(w.clamp(checksum, tlen), w.bitSlice(ciphertext, len))) {
      throw new sjcl.exception.corrupt("ocb: tag doesn't match");
    }
    
    return output.concat(w.clamp(bi,bl));
  },
  
  /** PMAC authentication for OCB associated data.
   * @param {Object} prp The block cipher.  It must have a block size of 16 bytes.
   * @param {bitArray} adata The authenticated data.
   */
  pmac: function(prp, adata) {
    var i,
        times2 = sjcl.mode.ocb2._times2,
        w = sjcl.bitArray,
        xor = w._xor4,
        checksum = [0,0,0,0],
        delta = prp.encrypt([0,0,0,0]),
        bi;
        
    delta = xor(delta,times2(times2(delta)));
 
    for (i=0; i+4<adata.length; i+=4) {
      delta = times2(delta);
      checksum = xor(checksum, prp.encrypt(xor(delta, adata.slice(i,i+4))));
    }
    
    bi = adata.slice(i);
    if (w.bitLength(bi) < 128) {
      delta = xor(delta,times2(delta));
      bi = w.concat(bi,[0x80000000|0,0,0,0]);
    }
    checksum = xor(checksum, bi);
    return prp.encrypt(xor(times2(xor(delta,times2(delta))), checksum));
  },
  
  /** Double a block of words, OCB style.
   * @private
   */
  _times2: function(x) {
    return [x[0]<<1 ^ x[1]>>>31,
            x[1]<<1 ^ x[2]>>>31,
            x[2]<<1 ^ x[3]>>>31,
            x[3]<<1 ^ (x[0]>>>31)*0x87];
  }
};
/** @fileOverview HMAC implementation.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** HMAC with the specified hash function.
 * @constructor
 * @param {bitArray} key the key for HMAC.
 * @param {Object} [hash=sjcl.hash.sha256] The hash function to use.
 */
sjcl.misc.hmac = function (key, Hash) {
  this._hash = Hash = Hash || sjcl.hash.sha256;
  var exKey = [[],[]], i,
      bs = Hash.prototype.blockSize / 32;
  this._baseHash = [new Hash(), new Hash()];

  if (key.length > bs) {
    key = Hash.hash(key);
  }
  
  for (i=0; i<bs; i++) {
    exKey[0][i] = key[i]^0x36363636;
    exKey[1][i] = key[i]^0x5C5C5C5C;
  }
  
  this._baseHash[0].update(exKey[0]);
  this._baseHash[1].update(exKey[1]);
};

/** HMAC with the specified hash function.  Also called encrypt since it's a prf.
 * @param {bitArray|String} data The data to mac.
 * @param {Codec} [encoding] the encoding function to use.
 */
sjcl.misc.hmac.prototype.encrypt = sjcl.misc.hmac.prototype.mac = function (data, encoding) {
  var w = new (this._hash)(this._baseHash[0]).update(data, encoding).finalize();
  return new (this._hash)(this._baseHash[1]).update(w).finalize();
};

/** @fileOverview Password-based key-derivation function, version 2.0.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** Password-Based Key-Derivation Function, version 2.0.
 *
 * Generate keys from passwords using PBKDF2-HMAC-SHA256.
 *
 * This is the method specified by RSA's PKCS #5 standard.
 *
 * @param {bitArray|String} password  The password.
 * @param {bitArray} salt The salt.  Should have lots of entropy.
 * @param {Number} [count=1000] The number of iterations.  Higher numbers make the function slower but more secure.
 * @param {Number} [length] The length of the derived key.  Defaults to the
                            output size of the hash function.
 * @param {Object} [Prff=sjcl.misc.hmac] The pseudorandom function family.
 * @return {bitArray} the derived key.
 */
sjcl.misc.pbkdf2 = function (password, salt, count, length, Prff) {
  count = count || 1000;
  
  if (length < 0 || count < 0) {
    throw sjcl.exception.invalid("invalid params to pbkdf2");
  }
  
  if (typeof password === "string") {
    password = sjcl.codec.utf8String.toBits(password);
  }
  
  Prff = Prff || sjcl.misc.hmac;
  
  var prf = new Prff(password),
      u, ui, i, j, k, out = [], b = sjcl.bitArray;

  for (k = 1; 32 * out.length < (length || 1); k++) {
    u = ui = prf.encrypt(b.concat(salt,[k]));
    
    for (i=1; i<count; i++) {
      ui = prf.encrypt(ui);
      for (j=0; j<ui.length; j++) {
        u[j] ^= ui[j];
      }
    }
    
    out = out.concat(u);
  }

  if (length) { out = b.clamp(out, length); }

  return out;
};
/** @fileOverview Random number generator.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */

/** @namespace Random number generator
 *
 * @description
 * <p>
 * This random number generator is a derivative of Ferguson and Schneier's
 * generator Fortuna.  It collects entropy from various events into several
 * pools, implemented by streaming SHA-256 instances.  It differs from
 * ordinary Fortuna in a few ways, though.
 * </p>
 *
 * <p>
 * Most importantly, it has an entropy estimator.  This is present because
 * there is a strong conflict here between making the generator available
 * as soon as possible, and making sure that it doesn't "run on empty".
 * In Fortuna, there is a saved state file, and the system is likely to have
 * time to warm up.
 * </p>
 *
 * <p>
 * Second, because users are unlikely to stay on the page for very long,
 * and to speed startup time, the number of pools increases logarithmically:
 * a new pool is created when the previous one is actually used for a reseed.
 * This gives the same asymptotic guarantees as Fortuna, but gives more
 * entropy to early reseeds.
 * </p>
 *
 * <p>
 * The entire mechanism here feels pretty klunky.  Furthermore, there are
 * several improvements that should be made, including support for
 * dedicated cryptographic functions that may be present in some browsers;
 * state files in local storage; cookies containing randomness; etc.  So
 * look for improvements in future versions.
 * </p>
 */
sjcl.random = {
  /** Generate several random words, and return them in an array
   * @param {Number} nwords The number of words to generate.
   */
  randomWords: function (nwords, paranoia) {
    var out = [], i, readiness = this.isReady(paranoia), g;
  
    if (readiness === this._NOT_READY) {
      throw new sjcl.exception.notready("generator isn't seeded");
    } else if (readiness & this._REQUIRES_RESEED) {
      this._reseedFromPools(!(readiness & this._READY));
    }
  
    for (i=0; i<nwords; i+= 4) {
      if ((i+1) % this._MAX_WORDS_PER_BURST === 0) {
        this._gate();
      }
   
      g = this._gen4words();
      out.push(g[0],g[1],g[2],g[3]);
    }
    this._gate();
  
    return out.slice(0,nwords);
  },
  
  setDefaultParanoia: function (paranoia) {
    this._defaultParanoia = paranoia;
  },
  
  /**
   * Add entropy to the pools.
   * @param data The entropic value.  Should be a 32-bit integer, array of 32-bit integers, or string
   * @param {Number} estimatedEntropy The estimated entropy of data, in bits
   * @param {String} source The source of the entropy, eg "mouse"
   */
  addEntropy: function (data, estimatedEntropy, source) {
    source = source || "user";
  
    var id,
      i, ty = 0, tmp,
      t = (new Date()).valueOf(),
      robin = this._robins[source],
      oldReady = this.isReady();
      
    id = this._collectorIds[source];
    if (id === undefined) { id = this._collectorIds[source] = this._collectorIdNext ++; }
      
    if (robin === undefined) { robin = this._robins[source] = 0; }
    this._robins[source] = ( this._robins[source] + 1 ) % this._pools.length;
  
    switch(typeof(data)) {
      
    case "number":
      data=[data];
      ty=1;
      break;
      
    case "object":
      if (estimatedEntropy === undefined) {
       /* horrible entropy estimator */
       estimatedEntropy = 0;
       for (i=0; i<data.length; i++) {
          tmp= data[i];
          while (tmp>0) {
           estimatedEntropy++;
           tmp = tmp >>> 1;
          }
        }
      }
      this._pools[robin].update([id,this._eventId++,ty||2,estimatedEntropy,t,data.length].concat(data));
      break;
      
    case "string":
      if (estimatedEntropy === undefined) {
       /* English text has just over 1 bit per character of entropy.
        * But this might be HTML or something, and have far less
        * entropy than English...  Oh well, let's just say one bit.
        */
       estimatedEntropy = data.length;
      }
      this._pools[robin].update([id,this._eventId++,3,estimatedEntropy,t,data.length]);
      this._pools[robin].update(data);
      break;
      
    default:
      
      throw new sjcl.exception.bug("random: addEntropy only supports number, array or string");
    }
  
    /* record the new strength */
    this._poolEntropy[robin] += estimatedEntropy;
    this._poolStrength += estimatedEntropy;
  
    /* fire off events */
    if (oldReady === this._NOT_READY) {
      if (this.isReady() !== this._NOT_READY) {
        this._fireEvent("seeded", Math.max(this._strength, this._poolStrength));
      }
      this._fireEvent("progress", this.getProgress());
    }
  },
  
  /** Is the generator ready? */
  isReady: function (paranoia) {
    var entropyRequired = this._PARANOIA_LEVELS[ (paranoia !== undefined) ? paranoia : this._defaultParanoia ];
  
    if (this._strength && this._strength >= entropyRequired) {
      return (this._poolEntropy[0] > this._BITS_PER_RESEED && (new Date()).valueOf() > this._nextReseed) ?
        this._REQUIRES_RESEED | this._READY :
        this._READY;
    } else {
      return (this._poolStrength >= entropyRequired) ?
        this._REQUIRES_RESEED | this._NOT_READY :
        this._NOT_READY;
    }
  },
  
  /** Get the generator's progress toward readiness, as a fraction */
  getProgress: function (paranoia) {
    var entropyRequired = this._PARANOIA_LEVELS[ paranoia ? paranoia : this._defaultParanoia ];
  
    if (this._strength >= entropyRequired) {
      return 1.0;
    } else {
      return (this._poolStrength > entropyRequired) ?
        1.0 :
        this._poolStrength / entropyRequired;
    }
  },
  
  /** start the built-in entropy collectors */
  startCollectors: function () {
    if (this._collectorsStarted) { return; }
  
    if (window.addEventListener) {
      window.addEventListener("load", this._loadTimeCollector, false);
      window.addEventListener("mousemove", this._mouseCollector, false);
    } else if (document.attachEvent) {
      document.attachEvent("onload", this._loadTimeCollector);
      document.attachEvent("onmousemove", this._mouseCollector);
    }
    else {
      throw new sjcl.exception.bug("can't attach event");
    }
  
    this._collectorsStarted = true;
  },
  
  /** stop the built-in entropy collectors */
  stopCollectors: function () {
    if (!this._collectorsStarted) { return; }
  
    if (window.removeEventListener) {
      window.removeEventListener("load", this._loadTimeCollector);
      window.removeEventListener("mousemove", this._mouseCollector);
    } else if (window.detachEvent) {
      window.detachEvent("onload", this._loadTimeCollector);
      window.detachEvent("onmousemove", this._mouseCollector);
    }
    this._collectorsStarted = false;
  },
  
  /* use a cookie to store entropy.
  useCookie: function (all_cookies) {
      throw new sjcl.exception.bug("random: useCookie is unimplemented");
  },*/
  
  /** add an event listener for progress or seeded-ness. */
  addEventListener: function (name, callback) {
    this._callbacks[name][this._callbackI++] = callback;
  },
  
  /** remove an event listener for progress or seeded-ness */
  removeEventListener: function (name, cb) {
    var i, j, cbs=this._callbacks[name], jsTemp=[];
  
    /* I'm not sure if this is necessary; in C++, iterating over a
     * collection and modifying it at the same time is a no-no.
     */
  
    for (j in cbs) {
	if (cbs.hasOwnProperty(j) && cbs[j] === cb) {
        jsTemp.push(j);
      }
    }
  
    for (i=0; i<jsTemp.length; i++) {
      j = jsTemp[i];
      delete cbs[j];
    }
  },
  
  /* private */
  _pools                   : [new sjcl.hash.sha256()],
  _poolEntropy             : [0],
  _reseedCount             : 0,
  _robins                  : {},
  _eventId                 : 0,
  
  _collectorIds            : {},
  _collectorIdNext         : 0,
  
  _strength                : 0,
  _poolStrength            : 0,
  _nextReseed              : 0,
  _key                     : [0,0,0,0,0,0,0,0],
  _counter                 : [0,0,0,0],
  _cipher                  : undefined,
  _defaultParanoia         : 6,
  
  /* event listener stuff */
  _collectorsStarted       : false,
  _callbacks               : {progress: {}, seeded: {}},
  _callbackI               : 0,
  
  /* constants */
  _NOT_READY               : 0,
  _READY                   : 1,
  _REQUIRES_RESEED         : 2,

  _MAX_WORDS_PER_BURST     : 65536,
  _PARANOIA_LEVELS         : [0,48,64,96,128,192,256,384,512,768,1024],
  _MILLISECONDS_PER_RESEED : 30000,
  _BITS_PER_RESEED         : 80,
  
  /** Generate 4 random words, no reseed, no gate.
   * @private
   */
  _gen4words: function () {
    for (var i=0; i<4; i++) {
      this._counter[i] = this._counter[i]+1 | 0;
      if (this._counter[i]) { break; }
    }
    return this._cipher.encrypt(this._counter);
  },
  
  /* Rekey the AES instance with itself after a request, or every _MAX_WORDS_PER_BURST words.
   * @private
   */
  _gate: function () {
    this._key = this._gen4words().concat(this._gen4words());
    this._cipher = new sjcl.cipher.aes(this._key);
  },
  
  /** Reseed the generator with the given words
   * @private
   */
  _reseed: function (seedWords) {
    this._key = sjcl.hash.sha256.hash(this._key.concat(seedWords));
    this._cipher = new sjcl.cipher.aes(this._key);
    for (var i=0; i<4; i++) {
      this._counter[i] = this._counter[i]+1 | 0;
      if (this._counter[i]) { break; }
    }
  },
  
  /** reseed the data from the entropy pools
   * @param full If set, use all the entropy pools in the reseed.
   */
  _reseedFromPools: function (full) {
    var reseedData = [], strength = 0, i;
  
    this._nextReseed = reseedData[0] =
      (new Date()).valueOf() + this._MILLISECONDS_PER_RESEED;
    
    for (i=0; i<16; i++) {
      /* On some browsers, this is cryptographically random.  So we might
       * as well toss it in the pot and stir...
       */
      reseedData.push(Math.random()*0x100000000|0);
    }
    
    for (i=0; i<this._pools.length; i++) {
     reseedData = reseedData.concat(this._pools[i].finalize());
     strength += this._poolEntropy[i];
     this._poolEntropy[i] = 0;
   
     if (!full && (this._reseedCount & (1<<i))) { break; }
    }
  
    /* if we used the last pool, push a new one onto the stack */
    if (this._reseedCount >= 1 << this._pools.length) {
     this._pools.push(new sjcl.hash.sha256());
     this._poolEntropy.push(0);
    }
  
    /* how strong was this reseed? */
    this._poolStrength -= strength;
    if (strength > this._strength) {
      this._strength = strength;
    }
  
    this._reseedCount ++;
    this._reseed(reseedData);
  },
  
  _mouseCollector: function (ev) {
    var x = ev.x || ev.clientX || ev.offsetX, y = ev.y || ev.clientY || ev.offsetY;
    sjcl.random.addEntropy([x,y], 2, "mouse");
  },
  
  _loadTimeCollector: function (ev) {
    var d = new Date();
    sjcl.random.addEntropy(d, 2, "loadtime");
  },
  
  _fireEvent: function (name, arg) {
    var j, cbs=sjcl.random._callbacks[name], cbsTemp=[];
    /* TODO: there is a race condition between removing collectors and firing them */ 

    /* I'm not sure if this is necessary; in C++, iterating over a
     * collection and modifying it at the same time is a no-no.
     */
  
    for (j in cbs) {
     if (cbs.hasOwnProperty(j)) {
        cbsTemp.push(cbs[j]);
     }
    }
  
    for (j=0; j<cbsTemp.length; j++) {
     cbsTemp[j](arg);
    }
  }
};

/** @fileOverview Convenince functions centered around JSON encapsulation.
 *
 * @author Emily Stark
 * @author Mike Hamburg
 * @author Dan Boneh
 */
 
 /** @namespace JSON encapsulation */
 sjcl.json = {
  /** Default values for encryption */
  defaults: { v:1, iter:1000, ks:128, ts:64, mode:"ccm", adata:"", cipher:"aes" },

  /** Simple encryption function.
   * @param {String|bitArray} password The password or key.
   * @param {String} plaintext The data to encrypt.
   * @param {Object} [params] The parameters including tag, iv and salt.
   * @param {Object} [rp] A returned version with filled-in parameters.
   * @return {String} The ciphertext.
   * @throws {sjcl.exception.invalid} if a parameter is invalid.
   */
  encrypt: function (password, plaintext, params, rp) {
    params = params || {};
    rp = rp || {};
    
    var j = sjcl.json, p = j._add({ iv: sjcl.random.randomWords(4,0) },
                                  j.defaults), tmp, prp;
    j._add(p, params);
    if (typeof p.salt === "string") {
      p.salt = sjcl.codec.base64.toBits(p.salt);
    }
    if (typeof p.iv === "string") {
      p.iv = sjcl.codec.base64.toBits(p.iv);
    }
    
    if (!sjcl.mode[p.mode] ||
        !sjcl.cipher[p.cipher] ||
        (typeof password === "string" && p.iter <= 100) ||
        (p.ts !== 64 && p.ts !== 96 && p.ts !== 128) ||
        (p.ks !== 128 && p.ks !== 192 && p.ks !== 256) ||
        (p.iv.length < 2 || p.iv.length > 4)) {
      throw new sjcl.exception.invalid("json encrypt: invalid parameters");
    }
    
    if (typeof password === "string") {
      tmp = sjcl.misc.cachedPbkdf2(password, p);
      password = tmp.key.slice(0,p.ks/32);
      p.salt = tmp.salt;
    }
    if (typeof plaintext === "string") {
      plaintext = sjcl.codec.utf8String.toBits(plaintext);
    }
    prp = new sjcl.cipher[p.cipher](password);
    
    /* return the json data */
    j._add(rp, p);
    rp.key = password;
    
    /* do the encryption */
    p.ct = sjcl.mode[p.mode].encrypt(prp, plaintext, p.iv, p.adata, p.tag);
    
    return j.encode(j._subtract(p, j.defaults));
  },
  
  /** Simple decryption function.
   * @param {String|bitArray} password The password or key.
   * @param {String} ciphertext The ciphertext to decrypt.
   * @param {Object} [params] Additional non-default parameters.
   * @param {Object} [rp] A returned object with filled parameters.
   * @return {String} The plaintext.
   * @throws {sjcl.exception.invalid} if a parameter is invalid.
   * @throws {sjcl.exception.corrupt} if the ciphertext is corrupt.
   */
  decrypt: function (password, ciphertext, params, rp) {
    params = params || {};
    rp = rp || {};
    
    var j = sjcl.json, p = j._add(j._add(j._add({},j.defaults),j.decode(ciphertext)), params, true), ct, tmp, prp;
    if (typeof p.salt === "string") {
      p.salt = sjcl.codec.base64.toBits(p.salt);
    }
    if (typeof p.iv === "string") {
      p.iv = sjcl.codec.base64.toBits(p.iv);
    }
    
    if (!sjcl.mode[p.mode] ||
        !sjcl.cipher[p.cipher] ||
        (typeof password === "string" && p.iter <= 100) ||
        (p.ts !== 64 && p.ts !== 96 && p.ts !== 128) ||
        (p.ks !== 128 && p.ks !== 192 && p.ks !== 256) ||
        (!p.iv) ||
        (p.iv.length < 2 || p.iv.length > 4)) {
      throw new sjcl.exception.invalid("json decrypt: invalid parameters");
    }
    
    if (typeof password === "string") {
      tmp = sjcl.misc.cachedPbkdf2(password, p);
      password = tmp.key.slice(0,p.ks/32);
      p.salt  = tmp.salt;
    }
    prp = new sjcl.cipher[p.cipher](password);
    
    /* do the decryption */
    ct = sjcl.mode[p.mode].decrypt(prp, p.ct, p.iv, p.adata, p.tag);
    
    /* return the json data */
    j._add(rp, p);
    rp.key = password;
    
    return sjcl.codec.utf8String.fromBits(ct);
  },
  
  /** Encode a flat structure into a JSON string.
   * @param {Object} obj The structure to encode.
   * @return {String} A JSON string.
   * @throws {sjcl.exception.invalid} if obj has a non-alphanumeric property.
   * @throws {sjcl.exception.bug} if a parameter has an unsupported type.
   */
  encode: function (obj) {
    var i, out='{', comma='';
    for (i in obj) {
      if (obj.hasOwnProperty(i)) {
        if (!i.match(/^[a-z0-9]+$/i)) {
          throw new sjcl.exception.invalid("json encode: invalid property name");
        }
        out += comma + i + ':';
        comma = ',';
        
        switch (typeof obj[i]) {
        case 'number':
        case 'boolean':
          out += obj[i];
          break;
          
        case 'string':
          out += '"' + escape(obj[i]) + '"';
          break;
        
        case 'object':
          out += '"' + sjcl.codec.base64.fromBits(obj[i],1) + '"';
          break;
        
        default:
          throw new sjcl.exception.bug("json encode: unsupported type");
        }
      }
    }
    return out+'}';
  },
  
  /** Decode a simple (flat) JSON string into a structure.  The ciphertext,
   * adata, salt and iv will be base64-decoded.
   * @param {String} str The string.
   * @return {Object} The decoded structure.
   * @throws {sjcl.exception.invalid} if str isn't (simple) JSON.
   */
  decode: function (str) {
    str = str.replace(/\s/g,'');
    if (!str.match(/^\{.*\}$/)) { 
      throw new sjcl.exception.invalid("json decode: this isn't json!");
    }
    var a = str.replace(/^\{|\}$/g, '').split(/,/), out={}, i, m;
    for (i=0; i<a.length; i++) {
      if (!(m=a[i].match(/^([a-z][a-z0-9]*):(?:(\d+)|"([a-z0-9+\/%*_.@=\-]*)")$/i))) {
        throw new sjcl.exception.invalid("json decode: this isn't json!");
      }
      if (m[2]) {
        out[m[1]] = parseInt(m[2],10);
      } else {
        out[m[1]] = m[1].match(/^(ct|salt|iv)$/) ? sjcl.codec.base64.toBits(m[3]) : unescape(m[3]);
      }
    }
    return out;
  },
  
  /** Insert all elements of src into target, modifying and returning target.
   * @param {Object} target The object to be modified.
   * @param {Object} src The object to pull data from.
   * @param {boolean} [requireSame=false] If true, throw an exception if any field of target differs from corresponding field of src.
   * @return {Object} target.
   * @private
   */
  _add: function (target, src, requireSame) {
    if (target === undefined) { target = {}; }
    if (src === undefined) { return target; }
    var i;
    for (i in src) {
      if (src.hasOwnProperty(i)) {
        if (requireSame && target[i] !== undefined && target[i] !== src[i]) {
          throw new sjcl.exception.invalid("required parameter overridden");
        }
        target[i] = src[i];
      }
    }
    return target;
  },
  
  /** Remove all elements of minus from plus.  Does not modify plus.
   * @private
   */
  _subtract: function (plus, minus) {
    var out = {}, i;
    
    for (i in plus) {
      if (plus.hasOwnProperty(i) && plus[i] !== minus[i]) {
        out[i] = plus[i];
      }
    }
    
    return out;
  },
  
  /** Return only the specified elements of src.
   * @private
   */
  _filter: function (src, filter) {
    var out = {}, i;
    for (i=0; i<filter.length; i++) {
      if (src[filter[i]] !== undefined) {
        out[filter[i]] = src[filter[i]];
      }
    }
    return out;
  }
};

/** Simple encryption function; convenient shorthand for sjcl.json.encrypt.
 * @param {String|bitArray} password The password or key.
 * @param {String} plaintext The data to encrypt.
 * @param {Object} [params] The parameters including tag, iv and salt.
 * @param {Object} [rp] A returned version with filled-in parameters.
 * @return {String} The ciphertext.
 */
sjcl.encrypt = sjcl.json.encrypt;

/** Simple decryption function; convenient shorthand for sjcl.json.decrypt.
 * @param {String|bitArray} password The password or key.
 * @param {String} ciphertext The ciphertext to decrypt.
 * @param {Object} [params] Additional non-default parameters.
 * @param {Object} [rp] A returned object with filled parameters.
 * @return {String} The plaintext.
 */
sjcl.decrypt = sjcl.json.decrypt;

/** The cache for cachedPbkdf2.
 * @private
 */
sjcl.misc._pbkdf2Cache = {};

/** Cached PBKDF2 key derivation.
 * @param {String} The password.  
 * @param {Object} The derivation params (iteration count and optional salt).
 * @return {Object} The derived data in key, the salt in salt.
 */
sjcl.misc.cachedPbkdf2 = function (password, obj) {
  var cache = sjcl.misc._pbkdf2Cache, c, cp, str, salt, iter;
  
  obj = obj || {};
  iter = obj.iter || 1000;
  
  /* open the cache for this password and iteration count */
  cp = cache[password] = cache[password] || {};
  c = cp[iter] = cp[iter] || { firstSalt: (obj.salt && obj.salt.length) ?
                     obj.salt.slice(0) : sjcl.random.randomWords(2,0) };
          
  salt = (obj.salt === undefined) ? c.firstSalt : obj.salt;
  
  c[salt] = c[salt] || sjcl.misc.pbkdf2(password, salt, obj.iter);
  return { key: c[salt].slice(0), salt:salt.slice(0) };
};