In which type of encryption do you encrypt and decrypt with the same shared secret key?

In symmetric encryption, the same shared secret key is used for both the processes of encryption and decryption. This means that both the sender and the receiver must possess the same key and keep it secret from anyone else. The simplicity and efficiency of symmetric encryption make it suitable for various applications, particularly when speed is a priority, as it tends to be less computationally intensive than its asymmetric counterpart.

In contrast, asymmetric encryption uses a pair of keys: a public key that can be shared freely and a private key that is kept secret. This method allows for secure communication without the need for both parties to share a common secret beforehand. Hashing, on the other hand, is not an encryption method; instead, it transforms data into a fixed-size string of characters, which is typically used for integrity checking rather than encryption. Digital signatures are a form of asymmetric cryptography used to verify the authenticity of a message and ensure the integrity of the data, but they do not serve the purpose of encrypting the data itself.

The nature of symmetric encryption and its reliance on a single shared key makes it a foundational aspect of secure communication, thus solidifying it as the correct choice for this question.