Definition
An authentication header (AH) is a component of the Internet Protocol security (IPsec) suite. It provides data origin authentication and connectionless integrity for IP datagrams. AH protects against replay attacks and ensures data isn’t intercepted during transit.
How Authentication Headers Work
AH adds a header (which includes information proving the sender’s identity and the integrity of the message) in the IP datagram. The sender generates a hash (a cryptographic checksum) with the original packet and shared secret key. On the other hand, the recipient verifies the hash using the same key to ensure the packet is authentic.
History of Authentication Headers
Authentication headers were introduced because of the increased need for secure transmission of information over the internet.
They were bundled in the IPsec protocol suite to address the issues of spoofing and data tampering in IP communications. Later, it was included in VPN solutions and network security architecture.