What is Cryptography

Throughout history, cryptography has empowered diplomats, soldiers, spies, and traders to safeguard written secrets, mirroring the privacy of face-to-face conversations by rendering information incomprehensible to outsiders. This core function – ensuring confidentiality, whether data is being transmitted ("in transit") or stored ("at rest") – remains central to cryptography's reputation today. Indeed, the Greek roots of "cryptography," meaning "secret writing," aptly describe this original purpose. 

However, the advent of information technology and data digitization following World War II spurred cryptography's evolution. It expanded to:

• Guarantee data integrity: preventing unauthorized modification without detection.

• Authenticate identity: verifying the source or author of data.

• Enable non-repudiation: ensuring individuals or entities cannot deny their association with data.

In essence, cryptography encompasses the practices, means, methods, and techniques used to transform data, providing confidentiality, integrity, authentication, and non-repudiation, or a combination thereof. In contrast, cryptology is the overarching study of secret messages, including both cryptography and cryptanalysis, the science of breaking cryptographic systems. Within cryptography, encryption employs a cipher to convert readable plaintext into unintelligible ciphertext, while decryption reverses this process. Therefore, in cryptographic terms, a method uses a cipher to transform plaintext into ciphertext and vice versa.