Cryptology splits into two complementary disciplines — what are they, and what does each one do?

Cryptography builds the protection (encryption); cryptanalysis tries to break it (extracting information from ciphertext).

Kryptologie (cryptology) is the umbrella term, divided into:

The two are in a permanent arms race: cryptographers design schemes, cryptanalysts attack them, and schemes that survive sustained cryptanalysis are the ones we trust.

Tip: "-grafie" = writing (building secrets), "-analyse" = breaking (taking them apart). Both together = cryptology.