Cryptoanalysis is the art of trying to discover the ciphertext and / or logic used in your encryption (key). The people who participate in this effort are called cryptanalysts. in other words, a cryotoanalysis is a "process of encoding the message" and therefore, the word that would best substitute words in parentheses is "cryptanalyst".
Neil deGrasse Tyson: Let’s celebrate the infinite variety in
the universe rather than ignore it and worry about just these nine
objects that have been discovered historically.