init method

void init(bool forEncryption, List<int> key)

Implementation

void init(bool forEncryption, List<int> key) {
  super.init(forEncryption, key);

  // Select 56 bits according to PC1
  var keyBits = new List<int?>.filled(56, null);
  for (var i = 0; i < 56; i++) {
    var keyBitPos = PC1[i] - 1;
    keyBits[i] = (rightShift32(
            this.key[rightShift32(keyBitPos, 5)], (31 - keyBitPos % 32))) &
        1;
  }

  // Assemble 16 subkeys
  var subKeys = this._subKeys = new List<List<int?>>.generate(16, (_) => []);
  for (var nSubKey = 0; nSubKey < 16; nSubKey++) {
    // Create subkey
    var subKey = subKeys[nSubKey] = new List<int?>.filled(24, 0);

    // Shortcut
    var bitShift = BIT_SHIFTS[nSubKey];

    // Select 48 bits according to PC2
    for (var i = 0; i < 24; i++) {
      // Select from the left 28 key bits
      subKey[(i ~/ 6) | 0] = subKey[(i ~/ 6) | 0]! |
          leftShift32(keyBits[((PC2[i] - 1) + bitShift) % 28]!, (31 - i % 6));

      // Select from the right 28 key bits
      subKey[4 + ((i ~/ 6) | 0)] = subKey[4 + ((i ~/ 6) | 0)]! |
          leftShift32(keyBits[28 + (((PC2[i + 24] - 1) + bitShift) % 28)]!,
              (31 - i % 6));
    }

    // Since each subkey is applied to an expanded 32-bit input,
    // the subkey can be broken into 8 values scaled to 32-bits,
    // which allows the key to be used without expansion
    subKey[0] = (subKey[0]! << 1).toSigned(32) | rightShift32(subKey[0]!, 31);
    for (var i = 1; i < 7; i++) {
      subKey[i] = rightShift32(subKey[i]!, ((i - 1) * 4 + 3));
    }
    subKey[7] =
        (subKey[7]! << 5).toSigned(32) | (rightShift32(subKey[7]!, 27));
  }
}