/*
 * AES Cipher function: encrypt 'input' with Rijndael algorithm
 *
 *   takes   byte-array 'input' (16 bytes)
 *           2D byte-array key schedule 'w' (Nr+1 x Nb bytes)
 *
 *   applies Nr rounds (10/12/14) using key schedule w for 'add round key' stage
 *
 *   returns byte-array encrypted value (16 bytes)
 */

AES = {

    /** Sbox is pre-computed multiplicative inverse in GF(2^8) used in SubBytes and KeyExpansion [§5.1.1] */
    Sbox : [
        0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
        0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
        0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
        0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
        0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
        0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
        0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
        0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
        0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
        0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
        0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
        0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
        0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
        0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
        0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
        0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16
    ],

    /** Rcon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2] */
    Rcon : [
        [0x00, 0x00, 0x00, 0x00],
        [0x01, 0x00, 0x00, 0x00],
        [0x02, 0x00, 0x00, 0x00],
        [0x04, 0x00, 0x00, 0x00],
        [0x08, 0x00, 0x00, 0x00],
        [0x10, 0x00, 0x00, 0x00],
        [0x20, 0x00, 0x00, 0x00],
        [0x40, 0x00, 0x00, 0x00],
        [0x80, 0x00, 0x00, 0x00],
        [0x1b, 0x00, 0x00, 0x00],
        [0x36, 0x00, 0x00, 0x00]
    ],

    /** main Cipher function [§5.1] */
    Cipher : function(input, w) {
        var Nb = 4;               // block size (in words): no of columns in state (fixed at 4 for AES)
        var Nr = w.length/Nb - 1; // no of rounds: 10/12/14 for 128/192/256-bit keys

        var state = [[],[],[],[]];  // initialise 4xNb byte-array 'state' with input [§3.4]
        for (var i=0; i<4*Nb; i++) state[i%4][Math.floor(i/4)] = input[i];

        state = this.AddRoundKey(state, w, 0, Nb);

        for (var round=1; round<Nr; round++) {
            state = this.SubBytes(state, Nb);
            state = this.ShiftRows(state, Nb);
            state = this.MixColumns(state, Nb);
            state = this.AddRoundKey(state, w, round, Nb);
        }

        state = this.SubBytes(state, Nb);
        state = this.ShiftRows(state, Nb);
        state = this.AddRoundKey(state, w, Nr, Nb);

        var output = new Array(4*Nb);  // convert state to 1-d array before returning [§3.4]
        for (var i=0; i<4*Nb; i++) output[i] = state[i%4][Math.floor(i/4)];
        return output;
    },

    /** apply SBox to state S [§5.1.1] */
    SubBytes : function(s, Nb) {
        for (var r=0; r<4; r++) {
            for (var c=0; c<Nb; c++) s[r][c] = this.Sbox[s[r][c]];
        }
        return s;
    },

    /** shift row r of state S left by r bytes [§5.1.2] */
    ShiftRows : function(s, Nb) {
        var t = new Array(4);
        for (var r=1; r<4; r++) {
            for (var c=0; c<4; c++) t[c] = s[r][(c+r)%Nb];  // shift into temp copy
            for (var c=0; c<4; c++) s[r][c] = t[c];         // and copy back
        }          // note that this will work for Nb=4,5,6, but not 7,8 (always 4 for AES):
        return s;  // see fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.311.pdf
    },

    /** combine bytes of each col of state S [§5.1.3] */
    MixColumns : function(s, Nb) {
        for (var c=0; c<4; c++) {
            var a = new Array(4);  // 'a' is a copy of the current column from 's'
            var b = new Array(4);  // 'b' is a•{02} in GF(2^8)
            for (var i=0; i<4; i++) {
                a[i] = s[i][c];
                b[i] = s[i][c]&0x80 ? s[i][c]<<1 ^ 0x011b : s[i][c]<<1;
            }
            // a[n] ^ b[n] is a•{03} in GF(2^8)
            s[0][c] = b[0] ^ a[1] ^ b[1] ^ a[2] ^ a[3]; // 2*a0 + 3*a1 + a2 + a3
            s[1][c] = a[0] ^ b[1] ^ a[2] ^ b[2] ^ a[3]; // a0 * 2*a1 + 3*a2 + a3
            s[2][c] = a[0] ^ a[1] ^ b[2] ^ a[3] ^ b[3]; // a0 + a1 + 2*a2 + 3*a3
            s[3][c] = a[0] ^ b[0] ^ a[1] ^ a[2] ^ b[3]; // 3*a0 + a1 + a2 + 2*a3
        }
        return s;
    },

    /** xor Round Key into state S [§5.1.4] */
    AddRoundKey : function(state, w, rnd, Nb) {
        for (var r=0; r<4; r++) {
            for (var c=0; c<Nb; c++) state[r][c] ^= w[rnd*4+c][r];
        }
        return state;
    },

    /** generate Key Schedule (byte-array Nr+1 x Nb) from Key [§5.2] */
    KeyExpansion : function(key) {
        var Nb = 4;            // block size (in words): no of columns in state (fixed at 4 for AES)
        var Nk = key.length/4  // key length (in words): 4/6/8 for 128/192/256-bit keys
        var Nr = Nk + 6;       // no of rounds: 10/12/14 for 128/192/256-bit keys

        var w = new Array(Nb*(Nr+1));
        var temp = new Array(4);

        for (var i=0; i<Nk; i++) {
            var r = [key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]];
            w[i] = r;
        }

        for (var i=Nk; i<(Nb*(Nr+1)); i++) {
            w[i] = new Array(4);
            for (var t=0; t<4; t++) temp[t] = w[i-1][t];
            if (i % Nk == 0) {
                temp = this.SubWord(this.RotWord(temp));
                for (var t=0; t<4; t++) temp[t] ^= this.Rcon[i/Nk][t];
            } else if (Nk > 6 && i%Nk == 4) {
                temp = this.SubWord(temp);
            }
            for (var t=0; t<4; t++) w[i][t] = w[i-Nk][t] ^ temp[t];
        }

        return w;
    },

    /** apply SBox to 4-byte word w */
    SubWord : function(w) {
        for (var i=0; i<4; i++) w[i] = this.Sbox[w[i]];
        return w;
    },

    /** rotate 4-byte word w left by one byte */
    RotWord : function(w) {
        var tmp = w[0];
        for (var i=0; i<3; i++) w[i] = w[i+1];
        w[3] = tmp;
        return w;
    },
    
    /**
     * Encrypt a text using AES encryption in Counter mode of operation
     *  - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
     *
     * Unicode multi-byte character safe
     *
     * @param plaintext source text to be encrypted
     * @param password  the password to use to generate a key
     * @param nBits     number of bits to be used in the key (128, 192, or 256)
     * @return          encrypted text
     */
    encrypt : function(plaintext, password, nBits) {
        var blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
        if (!(nBits==128 || nBits==192 || nBits==256)) return '';  // standard allows 128/192/256 bit keys
        plaintext = plaintext.encodeUTF8();
        password = password.encodeUTF8();
        //var t = new Date();  // timer

        // use AES itself to encrypt password to get cipher key (using plain password as source for key
        // expansion) - gives us well encrypted key
        var nBytes = nBits/8;  // no bytes in key
        var pwBytes = new Array(nBytes);
        for (var i=0; i<nBytes; i++) {
            pwBytes[i] = isNaN(password.charCodeAt(i)) ? 0 : password.charCodeAt(i);
        }
        var key = this.Cipher(pwBytes, this.KeyExpansion(pwBytes));  // gives us 16-byte key
        key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long

        // initialise counter block (NIST SP800-38A §B.2): millisecond time-stamp for nonce in 1st 8 bytes,
        // block counter in 2nd 8 bytes
        var counterBlock = new Array(blockSize);
        var nonce = (new Date()).getTime();  // timestamp: milliseconds since 1-Jan-1970
        var nonceSec = Math.floor(nonce/1000);
        var nonceMs = nonce%1000;
        // encode nonce with seconds in 1st 4 bytes, and (repeated) ms part filling 2nd 4 bytes
        for (var i=0; i<4; i++) counterBlock[i] = (nonceSec >>> i*8) & 0xff;
        for (var i=0; i<4; i++) counterBlock[i+4] = nonceMs & 0xff;
        // and convert it to a string to go on the front of the ciphertext
        var ctrTxt = '';
        for (var i=0; i<8; i++) ctrTxt += String.fromCharCode(counterBlock[i]);

        // generate key schedule - an expansion of the key into distinct Key Rounds for each round
        var keySchedule = this.KeyExpansion(key);

        var blockCount = Math.ceil(plaintext.length/blockSize);
        var ciphertxt = new Array(blockCount);  // ciphertext as array of strings

        for (var b=0; b<blockCount; b++) {
            // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
            // done in two stages for 32-bit ops: using two words allows us to go past 2^32 blocks (68GB)
            for (var c=0; c<4; c++) counterBlock[15-c] = (b >>> c*8) & 0xff;
            for (var c=0; c<4; c++) counterBlock[15-c-4] = (b/0x100000000 >>> c*8)

            var cipherCntr = this.Cipher(counterBlock, keySchedule);  // -- encrypt counter block --

            // block size is reduced on final block
            var blockLength = b<blockCount-1 ? blockSize : (plaintext.length-1)%blockSize+1;
            var cipherChar = new Array(blockLength);

            for (var i=0; i<blockLength; i++) {  // -- xor plaintext with ciphered counter char-by-char --
                cipherChar[i] = cipherCntr[i] ^ plaintext.charCodeAt(b*blockSize+i);
                cipherChar[i] = String.fromCharCode(cipherChar[i]);
            }
            ciphertxt[b] = cipherChar.join('');
        }

        // Array.join is more efficient than repeated string concatenation
        var ciphertext = ctrTxt + ciphertxt.join('');
        ciphertext = ciphertext.encodeBase64();  // encode in base64

        //alert((new Date()) - t);
        return ciphertext;
    },

    /**
     * Decrypt a text encrypted by AES in counter mode of operation
     *
     * @param ciphertext source text to be encrypted
     * @param password   the password to use to generate a key
     * @param nBits      number of bits to be used in the key (128, 192, or 256)
     * @return           decrypted text
     */
    decrypt : function(ciphertext, password, nBits) {
        var blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
        if (!(nBits==128 || nBits==192 || nBits==256)) return '';  // standard allows 128/192/256 bit keys
        ciphertext = ciphertext.decodeBase64();
        password = password.encodeUTF8();
        //var t = new Date();  // timer

        // use AES to encrypt password (mirroring encrypt routine)
        var nBytes = nBits/8;  // no bytes in key
        var pwBytes = new Array(nBytes);
        for (var i=0; i<nBytes; i++) {
            pwBytes[i] = isNaN(password.charCodeAt(i)) ? 0 : password.charCodeAt(i);
        }
        var key = this.Cipher(pwBytes, this.KeyExpansion(pwBytes));
        key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long

        // recover nonce from 1st 8 bytes of ciphertext
        var counterBlock = new Array(8);
        var ctrTxt = ciphertext.slice(0, 8);
        for (var i=0; i<8; i++) counterBlock[i] = ctrTxt.charCodeAt(i);

        // generate key schedule
        var keySchedule = this.KeyExpansion(key);

        // separate ciphertext into blocks (skipping past initial 8 bytes)
        var nBlocks = Math.ceil((ciphertext.length-8) / blockSize);
        var ct = new Array(nBlocks);
        for (var b=0; b<nBlocks; b++) ct[b] = ciphertext.slice(8+b*blockSize, 8+b*blockSize+blockSize);
        ciphertext = ct;  // ciphertext is now array of block-length strings

        // plaintext will get generated block-by-block into array of block-length strings
        var plaintxt = new Array(ciphertext.length);

        for (var b=0; b<nBlocks; b++) {
            // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
            for (var c=0; c<4; c++) counterBlock[15-c] = ((b) >>> c*8) & 0xff;
            for (var c=0; c<4; c++) counterBlock[15-c-4] = (((b+1)/0x100000000-1) >>> c*8) & 0xff;

            var cipherCntr = this.Cipher(counterBlock, keySchedule);  // encrypt counter block

            var plaintxtByte = new Array(ciphertext[b].length);
            for (var i=0; i<ciphertext[b].length; i++) {
                // -- xor plaintxt with ciphered counter byte-by-byte --
                plaintxtByte[i] = cipherCntr[i] ^ ciphertext[b].charCodeAt(i);
                plaintxtByte[i] = String.fromCharCode(plaintxtByte[i]);
            }
            plaintxt[b] = plaintxtByte.join('');
        }

        // join array of blocks into single plaintext string
        var plaintext = plaintxt.join('');
        plaintext = plaintext.decodeUTF8();  // decode from UTF8 back to Unicode multi-byte chars

        //alert((new Date()) - t);
        return plaintext;
    }
    
};


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

/**
 * Encode string into Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648]
 * (instance method extending String object). As per RFC 4648, no newlines are added.
 *
 * @param utf8encode optional parameter, if set to true Unicode string is encoded to UTF8 before 
 *                   conversion to base64; otherwise string is assumed to be 8-bit characters
 * @return           base64-encoded string
 */ 
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

String.prototype.encodeBase64 = function(utf8encode) {  // http://tools.ietf.org/html/rfc4648
    utf8encode =  (typeof utf8encode == 'undefined') ? false : utf8encode;
    var o1, o2, o3, bits, h1, h2, h3, h4, e=[], pad = '', c, plain, coded;
   
    plain = utf8encode ? this.encodeUTF8() : this;
  
    c = plain.length % 3;  // pad string to length of multiple of 3
    if (c > 0) {
        while (c++ < 3) {
            pad += '='; plain += '\0';
        }
    }
    // note: doing padding here saves us doing special-case packing for trailing 1 or 2 chars
  
    for (c=0; c<plain.length; c+=3) {  // pack three octets into four hexets
        o1 = plain.charCodeAt(c);
        o2 = plain.charCodeAt(c+1);
        o3 = plain.charCodeAt(c+2);
      
        bits = o1<<16 | o2<<8 | o3;
      
        h1 = bits>>18 & 0x3f;
        h2 = bits>>12 & 0x3f;
        h3 = bits>>6 & 0x3f;
        h4 = bits & 0x3f;

        // use hextets to index into b64 string
        e[c/3] = b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
    }
    coded = e.join('');  // join() is far faster than repeated string concatenation
  
    // replace 'A's from padded nulls with '='s
    coded = coded.slice(0, coded.length-pad.length) + pad;
   
    return coded;
}

/**
 * Decode string from Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648]
 * (instance method extending String object). As per RFC 4648, newlines are not catered for.
 *
 * @param utf8decode optional parameter, if set to true UTF8 string is decoded back to Unicode  
 *                   after conversion from base64
 * @return           decoded string
 */ 
String.prototype.decodeBase64 = function(utf8decode) {
    utf8decode =  (typeof utf8decode == 'undefined') ? false : utf8decode;
    var o1, o2, o3, h1, h2, h3, h4, bits, d=[], plain, coded;

    coded = utf8decode ? this.decodeUTF8() : this;
  
    for (var c=0; c<coded.length; c+=4) {  // unpack four hexets into three octets
        h1 = b64.indexOf(coded.charAt(c));
        h2 = b64.indexOf(coded.charAt(c+1));
        h3 = b64.indexOf(coded.charAt(c+2));
        h4 = b64.indexOf(coded.charAt(c+3));
      
        bits = h1<<18 | h2<<12 | h3<<6 | h4;
      
        o1 = bits>>>16 & 0xff;
        o2 = bits>>>8 & 0xff;
        o3 = bits & 0xff;
    
        d[c/4] = String.fromCharCode(o1, o2, o3);
        // check for padding
        if (h4 == 0x40) d[c/4] = String.fromCharCode(o1, o2);
        if (h3 == 0x40) d[c/4] = String.fromCharCode(o1);
    }
    plain = d.join('');  // join() is far faster than repeated string concatenation
   
    return utf8decode ? plain.decodeUTF8() : plain;
}

/**
 * Encode multi-byte Unicode string into utf-8 multiple single-byte characters 
 * (BMP / basic multilingual plane only) (instance method extending String object).
 *
 * Chars in range U+0080 - U+07FF are encoded in 2 chars, U+0800 - U+FFFF in 3 chars
 *
 * @return encoded string
 */
String.prototype.encodeUTF8 = function() {
    // use regular expressions & String.replace callback function for better efficiency
    // than procedural approaches
    var str = this.replace(
        /[\u0080-\u07ff]/g,  // U+0080 - U+07FF => 2 bytes 110yyyyy, 10zzzzzz
        function(c) {
            var cc = c.charCodeAt(0);
            return String.fromCharCode(0xc0 | cc>>6, 0x80 | cc&0x3f);
        }
        );
    str = str.replace(
        /[\u0800-\uffff]/g,  // U+0800 - U+FFFF => 3 bytes 1110xxxx, 10yyyyyy, 10zzzzzz
        function(c) {
            var cc = c.charCodeAt(0);
            return String.fromCharCode(0xe0 | cc>>12, 0x80 | cc>>6&0x3F, 0x80 | cc&0x3f);
        }
        );
    return str;
}

/**
 * Decode utf-8 encoded string back into multi-byte Unicode characters
 * (instance method extending String object).
 *
 * @return decoded string
 */
String.prototype.decodeUTF8 = function() {
    var str = this.replace(
        /[\u00c0-\u00df][\u0080-\u00bf]/g,                 // 2-byte chars
        function(c) {  // (note parentheses for precence)
            var cc = (c.charCodeAt(0)&0x1f)<<6 | c.charCodeAt(1)&0x3f;
            return String.fromCharCode(cc);
        }
        );
    str = str.replace(
        /[\u00e0-\u00ef][\u0080-\u00bf][\u0080-\u00bf]/g,  // 3-byte chars
        function(c) {  // (note parentheses for precence)
            var cc = ((c.charCodeAt(0)&0x0f)<<12) | ((c.charCodeAt(1)&0x3f)<<6) | ( c.charCodeAt(2)&0x3f);
            return String.fromCharCode(cc);
        }
        );
    return str;
}