Which hashing algorithm does NTP use for authentication?

NTP uses MD5 (Message Digest 5) for authentication. MD5 creates a 128-bit hash of the NTP packet and a shared secret key, ensuring both data integrity and authenticity. This prevents unauthorized time updates and tampering. While MD5 is considered cryptographically weak for other applications due to collision vulnerabilities, its use in NTP for integrity checking with a shared secret remains effective for many deployments. SSL is a protocol, not a hashing algorithm. AES128 and AES256 are symmetric encryption algorithms, not hashing algorithms, and are used for data confidentiality, not integrity or authentication in NTP.