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xtea.js
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xtea.js
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var Buffer = require('buffer').Buffer;
var ROUNDS = 32;
var DELTA = 0x9E3779B9;
/** @private */
function encipher( v, k ) {
var y = v[0];
var z = v[1];
var sum = 0;
var limit = (DELTA * ROUNDS) >>> 0;
while ( sum !== limit ) {
y += (((z << 4) >>> 0 ^ (z >>> 5)) + z) ^ (sum + k[sum & 3]);
y = y >>> 0;
sum = (sum + DELTA) >>> 0;
z += (((y << 4) >>> 0 ^ (y >>> 5)) + y) ^ (sum + k[(sum >> 11) & 3]);
z = z >>> 0;
}
v[0] = y;
v[1] = z;
}
/** @private */
function decipher( v, k ) {
var y = v[0];
var z = v[1];
var sum = (DELTA * ROUNDS) >>> 0;
while (sum) {
z -= (((y << 4) >>> 0 ^ (y >>> 5)) + y) ^ (sum + k[(sum >> 11) & 3]);
z = z >>> 0;
sum = (sum - DELTA) >>> 0;
y -= (((z << 4) >>> 0 ^ (z >>> 5)) + z) ^ (sum + k[sum & 3]);
y = y >>> 0;
}
v[0] = y;
v[1] = z;
}
/** @private */
function encipher_cbc( v, k, iv ) {
v[0] ^= iv[0];
v[1] ^= iv[1];
encipher( v, k );
iv[0] = v[0];
iv[1] = v[1];
}
/** @private */
function decipher_cbc( v, k, iv ) {
var tmp = new Uint32Array(v);
decipher( v, k );
v[0] ^= iv[0];
v[1] ^= iv[1];
iv[0] = tmp[0];
iv[1] = tmp[1];
}
/** @private */
function doBlock( method, block ,key ) {
var k = new Uint32Array(4);
var v = new Uint32Array(2);
var out = Buffer.allocUnsafe(8);
for (var i = 0; i < 4; ++i) {
k[i] = key.readUInt32BE(i * 4);
}
v[0] = block.readUInt32BE(0);
v[1] = block.readUInt32BE(4);
method( v, k );
out.writeUInt32BE(v[0], 0);
out.writeUInt32BE(v[1], 4);
return out
}
var MODES = {
ecb: { encrypt: encipher, decrypt: decipher },
cbc: { encrypt: encipher_cbc, decrypt: decipher_cbc }
}
/** @private */
function doBlocks( encryption, msg, key, mode, ivbuf, skippad ) {
mode = mode || 'ecb';
if (!ivbuf) {
ivbuf = Buffer.allocUnsafe(8);
ivbuf.fill(0);
}
var mode_ = MODES[ mode ];
if (!mode_) {
throw new Error('Unimplemented mode: ' + mode);
}
var method;
if (encryption) {
method = mode_.encrypt;
} else {
method = mode_.decrypt;
}
var length = msg.length;
var pad = 8 - (length & 7);
if ( skippad || ! encryption ) {
if (pad !== 8) {
throw new Error("Data not aligned to 8 bytes block boundary");
}
pad = 0;
}
var out = Buffer.allocUnsafe(length + pad);
var k = new Uint32Array(4);
var v = new Uint32Array(2);
var iv = new Uint32Array(2);
iv[0] = ivbuf.readUInt32BE(0);
iv[1] = ivbuf.readUInt32BE(4);
for (var i = 0; i < 4; ++i) {
k[i] = key.readUInt32BE(i * 4);
}
var offset = 0;
while (offset <= length) {
if (length - offset < 8) {
if ( skippad || ! encryption ) {
break;
}
var buf = Buffer.allocUnsafe( pad );
buf.fill( pad );
buf = Buffer.concat([ msg.slice( offset ), buf ]);
v[0] = buf.readUInt32BE( 0 );
v[1] = buf.readUInt32BE( 4 );
} else {
v[0] = msg.readUInt32BE( offset );
v[1] = msg.readUInt32BE( offset + 4 );
}
method( v, k, iv );
out.writeUInt32BE( v[0], offset );
out.writeUInt32BE( v[1], offset + 4 );
offset += 8;
}
if ( skippad || encryption )
return out;
var pad = out[out.length - 1];
return out.slice(0, out.length - pad);
}
/**
* Encrypts single block of data using XTEA cipher.
*
* @param {Buffer} block 64-bit (8-bytes) block of data to encrypt
* @param {Buffer} key 128-bit (16-bytes) encryption key
* @returns {Buffer} 64-bit of encrypted block
*/
function encryptBlock( block, key ) {
return doBlock( encipher, block, key );
}
/**
* Decrypts single block of data using XTEA cipher.
*
* @param {Buffer} block 64-bit (8-bytes) block of data to encrypt
* @param {Buffer} key 128-bit (16-bytes) encryption key
* @returns {Buffer} 64-bit of encrypted block
*/
function decryptBlock( block, key ) {
return doBlock( decipher, block, key );
}
/**
* Encrypts data using XTEA cipher using specified block cipher mode of operation
* and PKCS#7 padding.
*
* @param {Buffer} msg Message to encrypt
* @param {Buffer} key 128-bit encryption key (16 bytes)
* @param {string} [mode=ecb] Block cipher mode of operation (currently only 'ecb' or 'cbc')
* @param {Buffer} [iv] Optional IV
* @param {bool} [skippad] Skip PKCS#7 padding postprocessing
* @returns {Buffer}
*/
function encrypt( msg, key, mode, ivbuf, skippad ) {
return doBlocks( true, msg, key, mode, ivbuf, skippad );
}
/**
* Decrypts data using XTEA cipher using specified block cipher mode of operation
* and PKCS#7 padding.
*
* @param {Buffer} msg Ciphertext to decrypt
* @param {Buffer} key 128-bit encryption key (16 bytes)
* @param {string} [mode=ecb] Block cipher mode of operation (currently only 'ecb' or 'cbc')
* @param {Buffer} [iv] Optional IV
* @param {bool} [skippad] Skip PKCS#7 padding postprocessing
* @returns {Buffer}
*/
function decrypt( msg, key, mode, ivbuf, skippad ) {
return doBlocks( false, msg, key, mode, ivbuf, skippad );
}
exports.encryptBlock = encryptBlock
exports.decryptBlock = decryptBlock
exports.encrypt = encrypt
exports.decrypt = decrypt
// vim: ts=2 sts=2 sw=2 et