@li0ard/kalyna/dist/modes/ctr.js

Kalyna (DSTU 7624:2014) cipher implementation in pure TypeScript

import { concatBytes, xor } from "@li0ard/gost3413/dist/utils.js";
const incrementCounterAt = (ctr, pos) => {
    let j = pos;
    while (j < ctr.length)
        if (++ctr[j++] != 0)
            break;
};
/**
 * Proceed data using the Counter (CTR) mode
 * @param cipherClass Initialized cipher class
 * @param data Data to be encrypted/decrypted
 * @param iv Initialization vector
 */
export const ctr = (cipherClass, data, iv) => {
    if (iv.length !== cipherClass.blockSize)
        throw new Error("Invalid IV size");
    const keystreamBlocks = [];
    const ctr = cipherClass.encrypt(iv);
    for (let i = 0; i < Math.ceil(data.length / cipherClass.blockSize); i++) {
        incrementCounterAt(ctr, 0);
        keystreamBlocks.push(cipherClass.encrypt(ctr));
    }
    return xor(concatBytes(...keystreamBlocks), data);
};