Cryptography is the practice of securing communication and data through techniques that allow information to be transmitted or stored securely. It uses algorithms to convert readable data (plaintext) into an unreadable form (ciphertext), protecting it from unauthorised access.

Only authorised parties, with the correct decryption key, can reverse this process and access the original data. Cryptography underpins many modern security protocols, such as SSL/TLS for secure web browsing and encryption of emails or files. It includes various methods, such as symmetric encryption, asymmetric encryption, and hashing.