Which of the following is a type of encryption that uses a single key to encrypt and decrypt data?

Asymmetric encryption uses a mathematically linked key pair - a public key for encryption and a separate private key for decryption - not a single shared key.

Database encryption refers to the application or use case of encrypting data at rest within a database, not a distinct type of key-based encryption scheme.

XML encryption is a W3C standard defining how to encrypt XML document content, which is an application layer specification, not a fundamental type of key-based encryption.

Symmetric encryption, also called secret-key or shared-key cryptography, uses the exact same key for both the encryption and decryption operations. This makes key distribution a critical security challenge, since both communicating parties must securely exchange the shared key before use. Common symmetric algorithms include AES, DES, and TripleDES.