@ksen/crypto-ts/lib/pad-zeropadding.ts

A cryptography algorithms library compatible with ES6 and TypeScript

/**
 * Zero padding strategy.
 */
export const ZeroPadding = {
  pad(data, blockSize) {
    const _data = data;

    // Shortcut
    const blockSizeBytes = blockSize * 4;

    // Pad
    _data.clamp();
    _data.sigBytes += blockSizeBytes - ((data.sigBytes % blockSizeBytes) || blockSizeBytes);
  },

  unpad(data) {
    const _data = data;

    // Shortcut
    const dataWords = _data.words;

    // Unpad
    for (let i = _data.sigBytes - 1; i >= 0; i -= 1) {
      if (((dataWords[i >>> 2] >>> (24 - (i % 4) * 8)) & 0xff)) {
        _data.sigBytes = i + 1;
        break;
      }
    }
  },
};