@hackbg/miscreant-esm/src/providers/soft/aes_ctr.dist.mjs

(ESM port) Misuse resistant symmetric encryption library providing AES-SIV (RFC 5297), AES-PMAC-SIV, and STREAM constructions

import Block from "../../internals/block.dist.mjs";
export default class SoftAesCtr {
  _counter;
  _buffer;
  _cipher;
  constructor(cipher) {
    this._cipher = cipher;
    this._counter = new Block();
    this._buffer = new Block();
  }
  clear() {
    this._buffer.clear();
    this._counter.clear();
    this._cipher.clear();
    return this;
  }
  async encryptCtr(iv, plaintext) {
    if (iv.length !== Block.SIZE) {
      throw new Error("CTR: iv length must be equal to cipher block size");
    }
    this._counter.data.set(iv);
    let bufferPos = Block.SIZE;
    const result = new Uint8Array(plaintext.length);
    for (let i = 0; i < plaintext.length; i++) {
      if (bufferPos === Block.SIZE) {
        this._buffer.copy(this._counter);
        this._cipher.encryptBlock(this._buffer);
        bufferPos = 0;
        incrementCounter(this._counter);
      }
      result[i] = plaintext[i] ^ this._buffer.data[bufferPos++];
    }
    return result;
  }
}
function incrementCounter(counter) {
  let carry = 1;
  for (let i = Block.SIZE - 1; i >= 0; i--) {
    carry += counter.data[i] & 0xff | 0;
    counter.data[i] = carry & 0xff;
    carry >>>= 8;
  }
}