Which type of encryption uses more than one key?

Asymmetric encryption is characterized by the use of two distinct keys: a public key and a private key. The public key is used to encrypt the data, and only the corresponding private key can decrypt it. This dual-key mechanism allows for secure communication between parties without needing to share a secret key beforehand, making it particularly useful in scenarios such as secure email and digital signatures.

In contrast, symmetric encryption relies on a single key for both encryption and decryption, meaning both parties must agree on this key in advance. Hash encryption is concerned with creating a fixed-size output from variable-length input for data integrity verification, not encryption and decryption. Block encryption refers to a method of encrypting data in blocks, but it can employ either symmetric or asymmetric techniques. Thus, the defining feature of asymmetric encryption is its dual-key structure, which enhances security and facilitates secure key exchange.