Cryptanalysis is the science of making encrypted data unencrypted.

Cryptanalysts

Practitioners of cryptanalysis are known as cryptanalysts.

Cryptanalysis in Context

A cryptographer will use cryptography to convert plaintext into ciphertext and a cryptanalyst will use cryptanalysis to attempt to turn that ciphertext back into plaintext.

Both the cryptographer and the cryptanalyst are cryptologists. Cryptography and cryptanalysis are the two sides of cryptology.