Authentication Header in Network Security

03.06.2020 Read
Authentication Header in Network Security

Ensuring authentication is one of the pillars in cyber security. That is why authentication header is one of the crucial practices. In this article, we will explain what authentication header is and how it can be useful for your organization.

Almost every cyber security and/or information security expert knows about the famous CIA triad: Confidentiality, Integrity and Availability. These three consist the pillars of data security.

Being one of the crucial parts of data security, integrity ensures that the data is not altered or tainted by an unauthorized party. As cyber attackers and hackers put increasingly more effort on intercepting with the data stream, integrity has become an even more important portion of information security. That is why the Authentication Header gained more prominence. In this article, we will discuss what the Authentication Header is and how it can help you protect your organization.

What is the Authentication Header?

The Authentication Header (abbreviated as AH) is a security mechanism that aims to help with authenticating the origins of packets of data that are transmitted under IP conditions (also known as the datagrams). Moreover, the Authentication Header plays a crucial role in ensuring the integrity of the information that is being sent and received.

The Authentication Header is mainly a protocol. It is an integral part of the Internet Protocol Security protocol suite since it confirms the source of a packet/datagram and makes sure that the contents of this packet/datagram are not changed during the transmission process. The Authentication Protocol can be applied in conjunction with the Internet Protocol that encapsulates the security payload or it can also be applied in a nested way.

How does the Authentication Protocol work?

The main function of the Authentication Protocol is, as its name suggests, authentication. It ensures the integrity of the transmitted datagram and checks the authenticity of its source. In order to fulfil its function, the authentication protocol must be placed between the IP header and any other layer of security protocol like TCP, UDP or IDMP. If a combination of various security protocols is used, the authentication protocol must be inserted before any other Internet Protocol Security header as well.

An authentication header consists of five distinct layers:

Next Header: Having a maximum length of 8 bits, this layer identifies the next header that uses the specified IP protocol ID.

Payload Length: This layer aims to identify the security association of the data transmission and it works in conjunction with the security protocol in use and the packet’s destination address.

Sequence Number: This layer is very essential since it offers an ironclad protection against replay attacks. The length of the sequence number may vary regarding various factors but it must be a multiple of 32-bit words. Moreover, sequence number is not allowed to cycle once it is set.

Integrity Check Value (abbreviated as ICV): As its name suggests, integrity check value is used to verify whether the transmission’s integrity is intact. In order to do so, the recipient calculates a unique hash value and compares this value to ICV number so that the integrity of the message can be verified.

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