What type of encryption involves sharing a single private key?

The correct answer is symmetric key encryption. In symmetric key encryption, the same key is used for both encrypting and decrypting the data. This means that both parties involved in the communication need to possess the same private key, and keeping this key secure is crucial for maintaining the confidentiality of the information being exchanged.

This method is efficient for encrypting large amounts of data and is often used in scenarios where a secure channel for sharing the key already exists. Unlike public key encryption or asymmetric encryption, where a pair of keys (a public key and a private key) is used, symmetric key encryption relies solely on one shared key, making it different in its approach to maintaining data security. Hashing, on the other hand, is not a method of encryption but rather creates a fixed-size output (hash) from input data without the intent of being decrypted, further distinguishing it from symmetric key encryption.