For that you need to divide the message in chunks and encrypt&authenticate each chunk. It's what GPG is going to do soon. There are some ad-hoc approaches for t

For that you need to divide the message in chunks and encrypt&authenticate each chunk. It's what GPG is going to do soon. There are some ad-hoc approaches for that procedure, but two interesting and well-constructed are STREAM and CHAIN: https://eprint.iacr.org/2015/189.pdf https://eprint.iacr.org/2015/189.pdf