What type of encryption requires all parties to share a single key?

Symmetric encryption is characterized by the requirement that all parties involved share a single, secret key. This key is used for both the encryption and decryption processes, meaning the same key is needed to encode the data and decode it back to its original form. This method is efficient for encrypting large amounts of data and is commonly used in various applications where speed and resource efficiency are priorities.

In scenarios where symmetric encryption is applied, the security of the communication relies heavily on the secrecy of the shared key. If the key is compromised, the security of the encrypted information is also at risk. This contrasts with asymmetric encryption, where pairs of keys (a public key and a private key) are used, allowing for more complex and flexible cryptographic systems. Hash encryption serves a different purpose, primarily ensuring data integrity and authenticity, without reversible encryption or a shared key. Public Key Infrastructure (PKI) utilizes asymmetric encryption but doesn't involve sharing a single key among all parties in the manner that symmetric encryption does.