OCTADE
@octade@soc.octade.net
Such a large number of texts being ciphered with the same key presents fodder for a fund of attacks. Key re-use is dangerous in such a scenario.
A master key is can be combined with a unique sub key or salt for each message for individual key derivation per message. The unique sub keys can be encrypted with the master key for additional security. Such keys and salts must be RNG sourced.