[Cryptography] Coded sentences

[mok-kong shen]

A codebook in classical crypto is a mapping from a chosen number of
normal or nonsense words to the corresponding intended words or even
phrases and sentences. Wouldn't a generalization of that idea, namely a
mapping from certain types of sentences to the corresponding intended
phrases or sentences, be much more versatile and useful in practice?
I mean e.g. a rather mundane sentence expressing the fact that some
friends came to visit us and we have together done something and that
they'll further travel to somewhere could be written in a quite large
number of different ways textually via varying the names of the
visitors and what we have jointly done etc. as well as via varying the
grammatical constructions of the sentence.

M. K. Shen