The practice of solving and writing encryptions is cryptography.
Here is a brief explanation of the terms:
- Cryptology: The broader field that encompasses both cryptography (the creation of codes) and cryptanalysis (the study of codes, particularly the breaking of them).
- Cryptography: The art and science of creating secure communication through codes and ciphers.
- Cryptanalysis: The study and practice of breaking codes and ciphers, essentially deciphering the encrypted information.
So, in the context of your question, the correct term is cryptography.