A cryptographic algorithm for encryption and decryption is called what?

A cryptographic algorithm for encryption and decryption is called what?

• A. Hash
• B. Protocol
• C. Cipher
• D. Signature

Answer: (C)

A cipher is the cryptographic algorithm used for encryption and decryption. It takes readable plaintext and, with a key, turns it into unreadable ciphertext; applying the reverse process with the appropriate key recovers the original text. Some ciphers use the same key for both directions (symmetric), while others use a pair of keys (asymmetric) for encryption and decryption. Other terms don’t describe an encryption/decryption mechanism. A hash function produces a fixed-size digest and is designed to be one-way, so you can’t reverse it to get the original data. A protocol is a set of rules for how entities communicate and negotiate security. A digital signature is used to verify the origin and integrity of data, not to encrypt and decrypt its contents. Because encryption and decryption are the defining roles of a cipher, it’s the correct term.

A cipher is the cryptographic algorithm used for encryption and decryption. It takes readable plaintext and, with a key, turns it into unreadable ciphertext; applying the reverse process with the appropriate key recovers the original text. Some ciphers use the same key for both directions (symmetric), while others use a pair of keys (asymmetric) for encryption and decryption.

Other terms don’t describe an encryption/decryption mechanism. A hash function produces a fixed-size digest and is designed to be one-way, so you can’t reverse it to get the original data. A protocol is a set of rules for how entities communicate and negotiate security. A digital signature is used to verify the origin and integrity of data, not to encrypt and decrypt its contents. Because encryption and decryption are the defining roles of a cipher, it’s the correct term.