Which type of encryption uses a pair of keys, one secret and one public?

The correct answer is that asymmetric encryption utilizes a pair of keys: one public and one private (or secret). This method allows for secure communication by enabling one party to encrypt data using the public key, which can be shared openly. Only the corresponding private key, held securely by the receiver, can decrypt that data. This dual-key structure is fundamental to many security protocols, such as those used in HTTPS for secure web browsing, because it allows for a secure exchange of information without needing to share the private key.

In contrast, symmetric encryption relies on a single shared key for both encryption and decryption, making it less suitable for scenarios where secure key distribution is problematic. Hash encryption, on the other hand, isn't directly about encrypting data for secure transmission but instead creates a fixed-size hash value from input data, primarily for data integrity verification. Block encryption refers to a method of encrypting data in fixed-size blocks, which can be implemented in either symmetric or asymmetric encryption but does not specify the use of key pairs.