Deifreerimine

Deifreerimine is the process of converting ciphertext back into plaintext using decryption algorithms and keys. It is the reverse operation of encryption and a fundamental function in modern cryptography and digital communication. Decryption requires knowledge of the decryption key and a compatible algorithm.

In symmetric cryptography, the same secret key is used for both encryption and decryption. In asymmetric cryptography, authorization to decrypt is granted by a private key that corresponds to a public key used to encrypt the data. Many systems use a hybrid approach: a random symmetric key encrypts the data, and that key is sent securely by encrypting it with a public key.

Common decryption algorithms and schemes include AES and ChaCha20-Poly1305 for symmetric decryption; RSA and Elliptic Curve variants for asymmetric decryption. Decryption must be performed correctly to preserve data integrity; many schemes provide authentication and integrity checks (for example AEAD modes).

Security considerations: the practicality of decryption rests on key secrecy, proper implementation, and resistance to attacks such as brute force, side-channel, or quantum threats. Weak keys, poor random number generation, or key leakage can compromise decryption. Post-quantum cryptography studies decryption under quantum adversaries and proposes larger key sizes or new algorithms.

History and usage: encrypted communications over the Internet rely on decryption at destinations; decryption is used in file protection, messaging, and secure protocols like TLS. The field emphasizes both the confidentiality of decrypted data and its integrity once decrypted.

See also: encryption, cryptography, key management, secure communication protocols.