What type of encryption uses a single key shared between sender and receiver?

The type of encryption that uses a single key shared between the sender and receiver is symmetric key encryption. This method relies on a single key to both encrypt and decrypt the data. The key must be kept secret and is shared only between the parties involved in the communication.

Symmetric key encryption is efficient and faster than other forms of encryption, making it suitable for encrypting large amounts of data. However, one of its primary challenges lies in the secure exchange of the key between the sender and receiver, as anyone with access to the key can decrypt the message.

While public key encryption, often referred to as asymmetric encryption, relies on a pair of keys (a public key and a private key) for secure communication, symmetric encryption simplifies the process by using just one key. The term "private key encryption" can also refer to symmetric encryption, but it is less commonly used compared to the term "symmetric key encryption." SSL (Secure Sockets Layer), now largely succeeded by TLS (Transport Layer Security), utilizes a combination of both symmetric and asymmetric encryption techniques, but it is not solely focused on the use of a single shared key.