private static byte[] xor(final byte[] x1, final byte[] x2) {
    byte[] out = new byte[x1.length];

    for (int i = x1.length - 1; i >= 0; i--) {
      out[i] = (byte) (x1[i] ^ x2[i]);
    }
    return out;
  }
Compute the bitwise XOR of two arrays of bytes. The arrays have to be of same length. No length
checking is performed.

@param x1 the first array
@param x2 the second array
@return x1 XOR x2
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/rlpx/framing/Framer.java