Ciphertext

Ciphertext is the result of encryption: a transformed version of plaintext created by applying an algorithm to the plaintext with a secret key (or key pair). The purpose is to conceal content from unauthorized readers, so the ciphertext should be unintelligible without access to the correct decryption key.

Encryption algorithms come in symmetric and asymmetric varieties. In symmetric encryption, the same key is used to both encrypt and decrypt. In asymmetric encryption, a public key encrypts and a private key decrypts. Ciphers also split into block ciphers, which operate on fixed-size blocks, and stream ciphers, which process data as a continuous stream. Common examples include AES and ChaCha20 for symmetric encryption, and RSA or elliptic-curve schemes for asymmetric encryption.

Ciphertext alone provides confidentiality when used correctly. To ensure data integrity and authenticity, encryption is often combined with a Message Authentication Code (MAC) or digital signatures, forming authenticated encryption or cryptographic protocols. Attacks may target implementation details, padding, or side channels, so the use of secure modes of operation and proper key management is essential.

Ciphertext is used to protect communications over networks, secure storage of sensitive data, and privacy-preserving computation. Its secure use depends on selecting appropriate algorithms, correct key generation and management, and adherence to current best practices in cryptography.