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CycleCrypt.js
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CycleCrypt.js
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/*requires Uint8Array, Uint32Array*/
import randomBytes from './lib/randomBytes';
import { str2buffer, view8, toString } from 'string-encode';
/**
* Variable size symmetric key encryption algorithm.
* The cipher-key is generated by cycling the input key with a variation of XorShift+ PRNG.
* The bigger the key-size, the longer the period.
*
* @param {String|ArrayBuffer} key The encryption key
* @param {String|ArrayBuffer|Boolean} salt
* If a string, use it as salt.
* If TRUE, generate salt.
* @param {Number} saltRounds - Number of rounds of initial state generated from salt ⊕ key
*/
export default function CycleCrypt(key, salt, saltRounds) {
const self = this;
key = str2buf(key);
if (salt === true || salt === undefined) {
salt = randomBytes(Math.min(256, key.byteLength << 1));
}
self.salt = salt;
self._key = key = saltKey(key, str2buf(salt), saltRounds);
}
Object.defineProperties(CycleCrypt.prototype, {
constructor: {
value: CycleCrypt,
},
/**
* Encrypt/decrypt the data and advance the internal state of the cipher-key.
*
* @param {String|ArrayBuffer} data Data to encrypt
*
* @return Uint8Array The encrypted/decrypted data
*/
_: {
value: function _(data) {
data = str2buf(data);
const { dataLength } = data;
if (!dataLength) return data;
const key = this._key;
let klen = key.length;
let len = data.length;
for (let i = 0, k = 0; i < len; ++i, ++k === klen && (k = 0)) {
if (!k) mixKey(key);
data[i] ^= key[k];
}
data = view8(data, 0, dataLength);
data.toString = toString;
return data;
}
},
/**
* Get the number of bytes in the key
*
* @return int
*/
keyByteSize: {
get() {
return this._key.byteLength;
}
}
});
// Static methods:
CycleCrypt.randomBytes = randomBytes; // Uint8Array
CycleCrypt.toString = toString;
CycleCrypt.str2buffer = str2buffer; // Uint8Array
CycleCrypt.str2buf = str2buf; // Uint32Array
// // CycleCrypt.buf2str = buf2str;
/**
* Use a variation of Xorshift+ to mix the key
*
* @param Uint32Array $key List of int32 values representing the key
* @param int $rounds Number of rounds to process the key
*
* @return array A mixed key
*/
function mixKey(key, rounds) {
let len = key.length;
let k = len > 1 ? key[len - 1] : 0;
if (rounds == undefined) rounds = 1;
while (rounds-- > 0) {
for (let $i = len; $i--;) {
let ki = $i % len;
k = key[ki] + k;
k ^= k << 13; // 19
k ^= k >>> 17; // 15
k ^= k << 5; // 27
// k >>>= 0;
key[ki] = k;
}
}
return key;
}
/**
* Use a variation of Xorshift+ to salt the key
*
* @param Uint32Array $key
* @param Uint32Array $salt
* @param int $rounds Number of rounds to mix the key
*
* @return array A mixed key
*/
function saltKey(key, salt, rounds) {
let klen = key.length;
let slen = salt.length;
if (!slen) return key;
// make a copy to avoid altering the input salt
salt = salt.slice();
let k = klen > 1 ? key[klen - 1] : 0;
let s = slen > 1 ? salt[slen - 1] : 0;
if (rounds == undefined) rounds = 1;
while (rounds-- > 0) {
for (let i = Math.max(klen, slen); i--;) {
let ki = i % klen;
let si = i % slen;
k = key[ki] + k;
s = salt[si] + s;
s ^= s << 13; // 19
s ^= s >>> 7; // 25
k ^= k << 11; // 21
k ^= k >>> 8; // 24
// s >>>= 0;
k += s;
// k >>>= 0;
key[ki] = k;
salt[si] = s;
}
}
return key;
}
function str2buf(str) {
if (!str || typeof str.byteLength != 'number') {
str = str2buffer(str);
}
else {
str = view8(str);
}
// Make sure the new buffer has a multiple of 4 byteLength
const { byteLength } = str;
let b = byteLength & 3;
let i;
// if(b) {
b = byteLength + (b && (4 - b));
i = new Uint8Array(b);
i.set(str);
// }
// else {
// b = byteLength;
// i = str.slice();
// }
str = new Uint32Array(i.buffer, i.byteOffset, b >> 2);
str.dataLength = byteLength;
return str;
}
// Unused
// function buf2str(buf) {
// return buffer2str(view8(buf));
// }