IPA: /krɪp.təˈlɒdʒ.ɪ.kəl/
KK: /krɪp.təˈlɒdʒ.ɪ.kəl/
Related to the study of codes and ciphers, especially in the context of secret communication.
The cryptological techniques used by the spies were highly advanced.
Cryptological → It is formed from "crypto-" (from Greek "kryptos", meaning hidden or secret) and "-logical" (from Greek "logia", meaning study or science). The word "cryptological" refers to the study of hidden or secret codes and ciphers.
Think of 'hidden' ('crypto-') and the 'study' of it ('-logical') — that's why cryptological means the study of hidden codes.