Explainer and Decipherment

explainer

(n.) One who explains; an expounder or expositor; a commentator; an interpreter.

Webster's Revised Unabridged Dictionary

decipherment

The activity of making clear or converting from code into plain text.
- usage: "a secret key or password is required for decryption"
- synonyms: decoding, decryption

(n.) The act of deciphering.

Webster's Revised Unabridged Dictionary