What type of cryptography uses a single key for both encryption and decryption?

The correct answer is symmetric cryptography, which is characterized by the use of a single key for both the encryption and decryption processes. In symmetric cryptography, the same key must be kept secret between the communicating parties, ensuring that only those possessing the key can access the encrypted data. This method is efficient and faster compared to asymmetric cryptography because it involves straightforward algorithms.

For example, when one party encrypts a message using the shared key, the same key must be used by the receiving party to decrypt that message. This reliance on a single key requires secure key management practices to prevent unauthorized access.

In contrast, asymmetric cryptography involves two different keys, a public key for encryption and a private key for decryption. Public key cryptography specifically employs this dual-key system to enhance security by enabling users to share their public key openly while safeguarding their private key.

Hash functions, on the other hand, do not involve keys for encryption and decryption at all. They take input data and produce a fixed-size hash value, primarily used for data integrity checks rather than for encrypting and decrypting information.

Thus, symmetric cryptography is fundamentally defined by its use of a single key for both processes, making it distinct from the other types mentioned.