ciphertexts

Ciphertexts are the output of a cryptographic encryption process. When a plaintext message is transformed by an encryption algorithm using a key, it becomes ciphertext, intended to be unreadable to anyone who does not possess the appropriate key. Decryption, using the corresponding key, restores the original plaintext.

There are two broad classes of encryption: symmetric and asymmetric. In symmetric encryption, the same key is used to encrypt and decrypt. In public-key (asymmetric) encryption, a public key encrypts and a private key decrypts. Common algorithms include AES and ChaCha20 for symmetric encryption, and RSA or elliptic-curve algorithms for asymmetric encryption. Ciphertext may be produced by streaming ciphers or block ciphers and often employs modes of operation and padding to ensure security properties.

Ciphertexts are designed to conceal content, providing confidentiality. Modern schemes also emphasize integrity and authenticity through authenticated encryption. However, ciphertext alone does not guarantee security; weaknesses can arise from poor key management, weak algorithms, incorrect mode usage, or side-channel leakage. Attacks are analyzed across scenarios such as ciphertext-only, chosen-plaintext, and chosen-ciphertext.

Applications of ciphertext include securing communications and protecting data at rest. Protocols like TLS rely on encryption to safeguard messages in transit, while encrypted storage protects data on disks and in backups. Ongoing cryptographic research continues to refine notions of security, improve performance, and address new threats, emphasizing the importance of using well-vetted algorithms and correct implementations.