The study and practice of examining and breaking cryptographic systems, understanding how they work, and finding methods to defeat or weaken them. It involves analyzing the encrypted data (ciphertext) to discover the hidden structures and derive the original information (plaintext) without necessarily having access to the secret key used. Cryptanalysis is used both for academic research to test the strength of encryption algorithms and by adversaries to compromise security systems. It encompasses a variety of techniques, such as frequency analysis, pattern detection, brute force attacks, and more sophisticated mathematical approaches.