Which statement best describes symmetric cryptography?

• A. Single key is used for encryption and decryption.
• B. Public and private keys are used for encryption and decryption.
• C. Hashing replaces encryption in data protection.
• D. Public keys alone are sufficient for encryption and decryption.

Answer: (A)

In symmetric cryptography, the same key is used to both encrypt and decrypt data. This shared secret enables fast protection of large amounts of information, with common algorithms like AES or DES used in practice. Because both sender and receiver need to know and protect this one key, secure key distribution and management are essential; if the key is exposed, confidentiality is compromised.

The other statements don’t fit symmetric cryptography: using a public and private key describes asymmetric cryptography, which relies on a paired key system rather than one shared secret. Hashing is a one-way function intended for data integrity and authentication, not for encrypting data to keep it confidential. And public keys alone aren’t sufficient for encryption and decryption—decryption requires the corresponding private key.