Of course it is possible to encrypt an unreliable unidirectional bitstream. (Tons of systems do this, eg. satellite video links.)<p>Contrary to what other commenters suggest, a proper stream cipher like ChaCha20 is not even needed. You could just use CTR mode, which turns any block cipher (like AES) in a stream cipher and prevents ciphertext bit errors from creating more plaintext bit errors. Also, transmit the counter every once in a while so that dropped packets don&#x27;t prevent you from decrypting subsequent packets.