Question about the key and nonce used in 2021/rust_file_encryption

[egbakou]

Thanks for sharing these useful samples. My question is: in production, should the key and nonce remain private or just the key (in this case, add the nonce to the cipher text as you did in this blog post https://kerkour.com/rust-file-encryption-chacha20poly1305-argon2)?

[sylvain101010]

Hi @egbakou ,

With XChaCha20Poly1305 (or AES-256-GCM if that matters) the nonce does not need to be kept secret.

It can be appended to the ciphertext like in the previous blog post, or distributed as metadata (I think the latter is more common in the real world: you get the encrypted file, and some metadata as JSON such as the fileID, the encrypted filename, the nonce... whatever your application requires)

[egbakou]

Thank you for your response @skerkour 🙂