Jesus often uses
code words so that sayings have more than one meaning.
All the meanings can be true. The encoded (literal) form makes (some) sense and the decoded form makes sense. In general:
Noun words can be code words. Pronouns can be ambiguous.
Verb words are carefully chosen to work in both contexts.
By definition, in the security field, a
code word is a word that needs to be substituted with another word (e.g., using a
code book) to determine the meaning. By definition, in the security field, a
secret code is a code whose meaning is to be obscured to anyone without the code book.
So Jesus, by definition, uses
secret codes. However, these codes appear to provide only authentication information (and warnings about certain heresies) but no special salvation knowledge - which is always is clear text.