lib.js

/**************************************
*
* Go see encrypt.js or decrypt.js
* This file has been coded using the implementation: http://www.movable-type.co.uk/scripts/aes.html
*
**************************************/
class Aes {

    /**
     * AES Cipher function: encrypt 'input' state with algorithm [§5.1];
     *   applies Nr rounds (10/12/14) using key schedule w for 'add round key' stage.
     *
     * @param   {number[]}   input - 16-byte (128-bit) input state array.
     * @param   {number[][]} w - Key schedule as 2D byte-array (Nr+1 × Nb bytes).
     * @returns {number[]}   Encrypted output state array.
     */
    static cipher(input, w) {
        const Nb = 4; // block size (in words): no of columns in state (fixed at 4 for AES)
        const Nr = w.length / Nb - 1; // no of rounds: 10/12/14 for 128/192/256-bit keys

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

        state = Aes.addRoundKey(state, w, 0, Nb);

        for (let round = 1; round < Nr; round++) {
            state = Aes.subBytes(state, Nb);
            state = Aes.shiftRows(state, Nb);
            state = Aes.mixColumns(state, Nb);
            state = Aes.addRoundKey(state, w, round, Nb);
        }

        state = Aes.subBytes(state, Nb);
        state = Aes.shiftRows(state, Nb);
        state = Aes.addRoundKey(state, w, Nr, Nb);

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

        return output;
    }


    /**
     * Perform key expansion to generate a key schedule from a cipher key [§5.2].
     *
     * @param   {number[]}   key - Cipher key as 16/24/32-byte array.
     * @returns {number[][]} Expanded key schedule as 2D byte-array (Nr+1 × Nb bytes).
     */
    static keyExpansion(key) {
        const Nb = 4; // block size (in words): no of columns in state (fixed at 4 for AES)
        const Nk = key.length / 4; // key length (in words): 4/6/8 for 128/192/256-bit keys
        const Nr = Nk + 6; // no of rounds: 10/12/14 for 128/192/256-bit keys

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

        // initialise first Nk words of expanded key with cipher key
        for (let i = 0; i < Nk; i++) {
            const r = [key[4 * i], key[4 * i + 1], key[4 * i + 2], key[4 * i + 3]];
            w[i] = r;
        }

        // expand the key into the remainder of the schedule
        for (let i = Nk; i < (Nb * (Nr + 1)); i++) {
            w[i] = new Array(4);
            for (let t = 0; t < 4; t++) temp[t] = w[i - 1][t];
            // each Nk'th word has extra transformation
            if (i % Nk == 0) {
                temp = Aes.subWord(Aes.rotWord(temp));
                for (let t = 0; t < 4; t++) temp[t] ^= Aes.rCon[i / Nk][t];
            }
            // 256-bit key has subWord applied every 4th word
            else if (Nk > 6 && i % Nk == 4) {
                temp = Aes.subWord(temp);
            }
            // xor w[i] with w[i-1] and w[i-Nk]
            for (let t = 0; t < 4; t++) w[i][t] = w[i - Nk][t] ^ temp[t];
        }

        return w;
    }


    /**
     * Apply SBox to state S [§5.1.1].
     *
     * @private
     */
    static subBytes(s, Nb) {
        for (let r = 0; r < 4; r++) {
            for (let c = 0; c < Nb; c++) s[r][c] = Aes.sBox[s[r][c]];
        }
        return s;
    }


    /**
     * Shift row r of state S left by r bytes [§5.1.2].
     *
     * @private
     */
    static shiftRows(s, Nb) {
        const t = new Array(4);
        for (let r = 1; r < 4; r++) {
            for (let c = 0; c < 4; c++) t[c] = s[r][(c + r) % Nb]; // shift into temp copy
            for (let 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;
    }


    /**
     * Combine bytes of each col of state S [§5.1.3].
     *
     * @private
     */
    static mixColumns(s, Nb) {
        for (let c = 0; c < Nb; c++) {
            const a = new Array(Nb); // 'a' is a copy of the current column from 's'
            const b = new Array(Nb); // 'b' is a•{02} in GF(2^8)
            for (let r = 0; r < 4; r++) {
                a[r] = s[r][c];
                b[r] = s[r][c] & 0x80 ? s[r][c] << 1 ^ 0x011b : s[r][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]; // {02}•a0 + {03}•a1 + a2 + a3
            s[1][c] = a[0] ^ b[1] ^ a[2] ^ b[2] ^ a[3]; // a0 • {02}•a1 + {03}•a2 + a3
            s[2][c] = a[0] ^ a[1] ^ b[2] ^ a[3] ^ b[3]; // a0 + a1 + {02}•a2 + {03}•a3
            s[3][c] = a[0] ^ b[0] ^ a[1] ^ a[2] ^ b[3]; // {03}•a0 + a1 + a2 + {02}•a3
        }
        return s;
    }


    /**
     * Xor Round Key into state S [§5.1.4].
     *
     * @private
     */
    static addRoundKey(state, w, rnd, Nb) {
        for (let r = 0; r < 4; r++) {
            for (let c = 0; c < Nb; c++) state[r][c] ^= w[rnd * 4 + c][r];
        }
        return state;
    }


    /**
     * Apply SBox to 4-byte word w.
     *
     * @private
     */
    static subWord(w) {
        for (let i = 0; i < 4; i++) w[i] = Aes.sBox[w[i]];
        return w;
    }


    /**
     * Rotate 4-byte word w left by one byte.
     *
     * @private
     */
    static rotWord(w) {
        const tmp = w[0];
        for (let i = 0; i < 3; i++) w[i] = w[i + 1];
        w[3] = tmp;
        return w;
    }


}


// sBox is pre-computed multiplicative inverse in GF(2^8) used in subBytes and keyExpansion [§5.1.1]
Aes.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]
Aes.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]
];
class AesCtr extends Aes {

    /**
     * Encrypt a text using AES encryption in Counter mode of operation.
     *
     * Unicode multi-byte character safe
     *
     * @param   {string} plaintext - Source text to be encrypted.
     * @param   {string} password - The password to use to generate a key for encryption.
     * @param   {number} nBits - Number of bits to be used in the key; 128 / 192 / 256.
     * @returns {string} Encrypted text.
     *
     * @example
     *   const encr = AesCtr.encrypt('big secret', 'pāşšŵōřđ', 256); // 'lwGl66VVwVObKIr6of8HVqJr'
     */
    static encrypt(plaintext, password, nBits) {
        const blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
        if (!(nBits == 128 || nBits == 192 || nBits == 256)) throw new Error('Key size is not 128 / 192 / 256');
        plaintext = AesCtr.utf8Encode(String(plaintext));
        password = AesCtr.utf8Encode(String(password));

        // use AES itself to encrypt password to get cipher key (using plain password as source for key
        // expansion) to give us well encrypted key (in real use hashed password could be used for key)
        const nBytes = nBits / 8; // no bytes in key (16/24/32)
        const pwBytes = new Array(nBytes);
        for (let i = 0; i < nBytes; i++) { // use 1st 16/24/32 chars of password for key
            pwBytes[i] = i < password.length ? password.charCodeAt(i) : 0;
        }
        let key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes)); // gives us 16-byte key
        key = key.concat(key.slice(0, nBytes - 16)); // expand key to 16/24/32 bytes long

        // initialise 1st 8 bytes of counter block with nonce (NIST SP800-38A §B.2): [0-1] = millisec,
        // [2-3] = random, [4-7] = seconds, together giving full sub-millisec uniqueness up to Feb 2106
        const counterBlock = new Array(blockSize);

        const nonce = (new Date()).getTime(); // timestamp: milliseconds since 1-Jan-1970
        const nonceMs = nonce % 1000;
        const nonceSec = Math.floor(nonce / 1000);
        const nonceRnd = Math.floor(Math.random() * 0xffff);
        // for debugging: nonce = nonceMs = nonceSec = nonceRnd = 0;

        for (let i = 0; i < 2; i++) counterBlock[i] = (nonceMs >>> i * 8) & 0xff;
        for (let i = 0; i < 2; i++) counterBlock[i + 2] = (nonceRnd >>> i * 8) & 0xff;
        for (let i = 0; i < 4; i++) counterBlock[i + 4] = (nonceSec >>> i * 8) & 0xff;

        // and convert it to a string to go on the front of the ciphertext
        let ctrTxt = '';
        for (let 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
        const keySchedule = Aes.keyExpansion(key);

        const blockCount = Math.ceil(plaintext.length / blockSize);
        let ciphertext = '';

        for (let 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 (let c = 0; c < 4; c++) counterBlock[15 - c] = (b >>> c * 8) & 0xff;
            for (let c = 0; c < 4; c++) counterBlock[15 - c - 4] = (b / 0x100000000 >>> c * 8);

            const cipherCntr = Aes.cipher(counterBlock, keySchedule); // -- encrypt counter block --

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

            for (let 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]);
            }
            ciphertext += cipherChar.join('');

            // if within web worker, announce progress every 1000 blocks (roughly every 50ms)
            if (typeof WorkerGlobalScope != 'undefined' && self instanceof WorkerGlobalScope) {
                if (b % 1000 == 0) self.postMessage({
                    progress: b / blockCount
                });
            }
        }

        ciphertext = AesCtr.base64Encode(ctrTxt + ciphertext);

        return ciphertext;
    }


    /**
     * Decrypt a text encrypted by AES in counter mode of operation
     *
     * @param   {string} ciphertext - Cipher text to be decrypted.
     * @param   {string} password - Password to use to generate a key for decryption.
     * @param   {number} nBits - Number of bits to be used in the key; 128 / 192 / 256.
     * @returns {string} Decrypted text
     *
     * @example
     *   const decr = AesCtr.decrypt('lwGl66VVwVObKIr6of8HVqJr', 'pāşšŵōřđ', 256); // 'big secret'
     */
    static decrypt(ciphertext, password, nBits) {
        const blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
        if (!(nBits == 128 || nBits == 192 || nBits == 256)) throw new Error('Key size is not 128 / 192 / 256');
        ciphertext = AesCtr.base64Decode(String(ciphertext));
        password = AesCtr.utf8Encode(String(password));

        // use AES to encrypt password (mirroring encrypt routine)
        const nBytes = nBits / 8; // no bytes in key
        const pwBytes = new Array(nBytes);
        for (let i = 0; i < nBytes; i++) { // use 1st nBytes chars of password for key
            pwBytes[i] = i < password.length ? password.charCodeAt(i) : 0;
        }
        let key = Aes.cipher(pwBytes, Aes.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
        const counterBlock = new Array(8);
        const ctrTxt = ciphertext.slice(0, 8);
        for (let i = 0; i < 8; i++) counterBlock[i] = ctrTxt.charCodeAt(i);

        // generate key schedule
        const keySchedule = Aes.keyExpansion(key);

        // separate ciphertext into blocks (skipping past initial 8 bytes)
        const nBlocks = Math.ceil((ciphertext.length - 8) / blockSize);
        const ct = new Array(nBlocks);
        for (let 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
        let plaintext = '';

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

            const cipherCntr = Aes.cipher(counterBlock, keySchedule); // encrypt counter block

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

            // if within web worker, announce progress every 1000 blocks (roughly every 50ms)
            if (typeof WorkerGlobalScope != 'undefined' && self instanceof WorkerGlobalScope) {
                if (b % 1000 == 0) self.postMessage({
                    progress: b / nBlocks
                });
            }
        }

        plaintext = AesCtr.utf8Decode(plaintext); // decode from UTF8 back to Unicode multi-byte chars

        return plaintext;
    }


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


    /**
     * Encodes multi-byte string to utf8.
     *
     * Note utf8Encode is an identity function with 7-bit ascii strings, but not with 8-bit strings;
     * utf8Encode('x') = 'x', but utf8Encode('ça') = 'ça', and utf8Encode('ça') = 'ça'.
     */
    static utf8Encode(str) {
        try {
            return new TextEncoder().encode(str, 'utf-8').reduce((prev, curr) => prev + String.fromCharCode(curr), '');
        } catch (e) { // no TextEncoder available?
            return unescape(encodeURIComponent(str)); // monsur.hossa.in/2012/07/20/utf-8-in-javascript.html
        }
    }

    /**
     * Decodes utf8 string to multi-byte.
     */
    static utf8Decode(str) {
        try {
            return new TextEncoder().decode(str, 'utf-8').reduce((prev, curr) => prev + String.fromCharCode(curr), '');
        } catch (e) { // no TextEncoder available?
            return decodeURIComponent(escape(str)); // monsur.hossa.in/2012/07/20/utf-8-in-javascript.html
        }
    }

    /*
     * Encodes string as base-64.
     *
     * - developer.mozilla.org/en-US/docs/Web/API/window.btoa, nodejs.org/api/buffer.html
     * - note: btoa & Buffer/binary work on single-byte Unicode (C0/C1), so ok for utf8 strings, not for general Unicode...
     * - note: if btoa()/atob() are not available (eg IE9-), try github.com/davidchambers/Base64.js
     */
    static base64Encode(str) {
        if (typeof btoa != 'undefined') return btoa(str); // browser
        if (typeof Buffer != 'undefined') return new Buffer(str, 'binary').toString('base64'); // Node.js
        throw new Error('No Base64 Encode');
    }

    /*
     * Decodes base-64 encoded string.
     */
    static base64Decode(str) {
        if (typeof atob != 'undefined') return atob(str); // browser
        if (typeof Buffer != 'undefined') return new Buffer(str, 'base64').toString('binary'); // Node.js
        throw new Error('No Base64 Decode');
    }

}
module.exports = {
	Aes: Aes,
	AesCtr: AesCtr
}