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What is IPsec (Internet Protocol Security)?
Updated on 16th May, 23 319 Views

What is IPsec?

IPsec (Internet Protocol Security) is used to secure sensitive data as it travels over the network, such as financial transactions, medical information, and business communications. IPsec tunneling is also used to protect virtual private networks (VPNs), where it encrypts all data exchanged between two endpoints. IPsec may also encrypt application layer data and protect routers providing routing data over the public internet. IPsec can also be used to offer authentication without encryption, such as confirming that data came from a recognized sender.

Encryption at the application or transport levels of the Open Systems Interconnection (OSI) paradigm enables protect data transmission without the need for IPsec. Encryption is performed at the application layer through Hypertext Transfer Protocol Secure (HTTPS). Encryption is provided at the transport layer by the Transport Layer Security (TLS) protocol. However, encrypting and authenticating at these higher layers increases the risk of data leakage and attackers intercepting protocol information.

In this blog, we’re going to dig up about the IPsec and you will get to know about IPsec uses and working.

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Table of Contents:

How does IPsec Operates?

IPsec operates in five phases. They are as follows:

How does IPsec Operates

Recognize the host:

When a host system decides that a packet needs protection and should be delivered using IPsec rules, the IPsec process starts.

Such packets are considered “interesting traffic” for IPsec reasons, and they engage security restrictions.

This shows that the necessary authentication and encryption are applied to departing packets.

The host system confirms that an incoming packet’s encryption and authentication have been done properly when it deems it to be interesting.

IKE Phase 1 or Negotiation:

The hosts utilize IPsec to discuss the rules for a secured circuit during the second phase.

Additionally, they confirm one another and provide a secure channel between them via which they may agree on how the IPsec circuit would encrypt or authenticate data sent over it.

Either the primary mode or the aggressive mode is used for this conversation.

When using the primary mode, the host making the connection offers suggestions for its preferred methods of authentication and encryption. Until both hosts agree and create an IKE SA that specifies the IPsec circuit they will use, the negotiating will carry on. Since it offers a secure channel for data transmission, this technique is much safer than the aggressive mode.

When in aggressive mode, the beginning host forbids negotiation and mandates the use of the IKE SA. The session is authenticated when the responding host accepts the request. Hosts can easily build an IPsec circuit using this method.

IKE Phase 2 or IPsec circuit:

Step 3 involves creating an IPsec circuit over the security gateway created in IKE Phase 1. The IPsec hosts agree on the data transmission algorithms to be used. Additionally, the hosts decide on and distribute decryption and encryption keys for communication to and from the secured network. The hosts also transmit different numbers known as cryptographic nonces, which are required to authenticate connections.

IPsec transit:

Through the secure channel they have built in the fourth stage, the hosts actually exchange data. The packets are encrypted and decoded using the previously set IPsec SAs.

Termination of IPsec:

The IPsec tunnel is finally terminated. Generally, this occurs after a specified volume of data has passed over the IPsec tunnel or after the transaction has expired. The hosts communicate when one of these events takes place, and the link is cut off. After the data transmission has terminated, the hosts delete the private keys that were utilized.

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Architecture of IPsec

The IPSec (IP Security) architecture utilizes two protocols to protect traffic or data transfers. These protocols are ESP and AH (Encapsulation Security Payload) (Authentication Header). The IPSec Architecture includes protocols, algorithms, DOI, and key management. All of these components are required to provide the three key services:

  • Confidentiality
  • Authentication
  • Integrity
Architecture of IPsec


The fundamental principles, definitions, protocols, algorithms, and security requirements of IP Security technology are covered in IP Security Architecture.

Encapsulation Security Payload

The secrecy service is provided by ESP (Encapsulation Security Payload). The Encapsulation Security Payload can be implemented in two ways:

  • ESP with optional authentication
  • ESP combined with authentication

Encryption algorithm

The encryption algorithm is a document that details the different encryption techniques used for Encapsulation Security Payload.

AH Protocol

The AH Protocol (Authentication Header) enables both authentication and integrity. The Authentication Header is used in just one way: Authentication and Integrity.

Authentication Algorithm

The authentication Algorithm is a set of files that define the authentication algorithm used for AH and the authentication option of ESP.

DOI (Domain of Interpretation)

A DOI is an identifier that can be used with both the AH and ESP protocols. It comprises values that are required for documentation and are connected to one another.

Key Management

The key management document outlines how keys are shared between sender and recipient.

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What are IPsec Protocols?

Data packets traveling across IPv4 and IPv6 networks are authenticated and encrypted using IPsec. The Internet protocol of a packet contains IPsec protocol headers, which govern how information in a packet is treated, including delivery and routing along a network. A number of additional elements, such as security data and one or more cryptographic techniques, are added to the IP header by IPsec.

A protocol in networking is a predefined method of structuring data so that any networked machine may comprehend it. IPsec is a protocol suite, not a single protocol. The IPsec suite consists of the following protocols:


RFC 4302 contains the AH protocol definition. It provides services for transport security and data integrity. AH was intended to be included in such an IP packet in order to add authentication information while simultaneously shielding the contents from alteration.

Encapsulating Security Protocol (ESP)

ESP encrypts both the IP header and the payload for each packet unless transport mode is enabled, in which case it just encrypts the payload. ESP appends its header and trailer to each data packet.

Internet Security Association and Key Management Protocol (ISAKMP)

Both RFC 7296 and the IKE protocol specify ISAKMP. This framework enables the establishment of a SA for encrypted packet exchange at the IP layer as well as the establishment of keys, user authentication, and SAs. In other words, ISAKMP defines the security parameters that control communication between two hosts or systems. Every Security Association specifies a one-way connection between two hosts. All connection-related details, including the cryptographic method, IPsec mode, encryption key, and any other factors affecting data transit over the link, are contained in the SA.


Two systems or devices can create a secure communication channel across an untrusted network using the IKE protocol, which is described in RFC 7296. In order to create a safe tunnel between a client and the server via which encrypted communication may be delivered, the protocol uses a series of crucial exchanges. The Diffie-Hellman key exchange provides the foundation for the tunnel’s security.

IPsec uses or is utilized by a large number of other protocols, including digital signature techniques and most of the protocols included in the IPsec and IKE Document Pathway, or RFC 607.

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What is the Purpose of IPsec?

  • IPsec is used to encrypt sensitive data traveling over networks, including banking transactions, health information, and corporate conversations.
  • Additionally, IPsec tunneling is used to safeguard virtual private networks (VPNs), which encrypt all data transferred between two endpoints.
  • Additionally, IPsec may provide security for networks relaying routing information across the open internet and encrypt application layer traffic.
  • IPsec can also be employed to provide identification without encrypting, such as when confirming the identity of the sender of data.
What is the Purpose of IPsec?
  • Instead of using IPsec, data transmission can be secured using encrypting at the service or transport layers of the Open Systems Interconnection (OSI) paradigm.
  • Through Hypertext Transfer Protocol Secure(HTTPS), encryption is carried out at the application layer.
  • At the transport layer, the Transport Layer Security (TLS) protocol offers encryption.
  • On the other side, encryption and authentication at these upper layers raise the danger of data loss and attackers eavesdropping on protocol data.

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What is IPsec VPN?

In its most basic form, a VPN is a secure network that is installed over a public site. Anyone with a VPN connection has the same level of access to the private network as someone who is physically connected to it. Businesses frequently use VPNs to give staff remote access to the company network.

A VPN that employs IPsec as its protocol to provide secure connections between devices is known as an IPsec VPN. SSL/TLS and L2TP are two other IPsec VPN protocols. Let’s have a look at these various IPsec protocols:

  • Transport Layer Security (TLS) is the successor to Secure Sockets Layer (SSL), which is a cryptographic IPsec protocol that provides communication security over a computer network. TLS is well recognized for providing security over HTTPS communications.
  • Internet Protocol Security (IPsec) is a secure network protocol that is used in VPNs to authenticate and encrypt data packets to offer secure communication.
  • Layer Tunneling Protocol (L2TP) is a tunneling protocol that is used to enable VPNs. L2TP does not provide robust authentication on its own. IPSec is frequently used to secure L2TP packets. The combination of these two protocols is known as L2TP/IPsec.

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What are the IPsec Modes?

IPSec can be set to function in two modes: tunnel and transport. The use of each mode is determined by the IPSec specifications and implementation.

What are the IPsec Modes?

IPsec tunnel mode which is frequently used across protected network ports enables hosts behind one gateway to securely communicate with hosts behind the other gateway.

For instance, users of systems in the branch office can securely connect to any systems in the main office if both the branch office and the main office have secure gateways that serve as IPsec proxies for hosts inside of their respective offices.

Despite the fact that the IPsec tunnel is constructed between the two portal hosts, it can transport traffic from any host inside the protected networks.

A mechanism for securing all communication between two networks coming from several hosts on either end must be established, and IPsec Tunnel mode is crucial for this.

Transport mode of transportation An IPsec circuit is created when two hosts join over a directly connected IPsec VPN.

For instance, this type of circuit may be set up to enable remote information technology (IT) and support personnel to connect to a remote server and carry out maintenance tasks.

The IPsec transport technique is used when two hosts need to communicate.

Direct negotiations between the two hosts establish the IPsec circuit, which is typically terminated once the session is over.

Uses of IPsec

 IPsec can be used to accomplish the following tasks:

  • To encrypt data at the application layer.
  • To secure routers that provide routing data via the public internet.
  • To give authentication without encryption, such as confirming that the data came from a recognized sender.
  • To secure network data, configure IPsec tunneling circuits in which all data transported between two endpoints is encrypted, similar to a Virtual Private Network (VPN) connection.

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Internet protocol security (IPsec) is a group of protocols that offer security for the Internet Protocol.SSL is a secure protocol designed for securely transmitting data over the Internet.    
It operates at the OSI model’s Internet Layer.It operates between the OSI model’s transport and application layers.
IPsec is used to secure a VPN.SSL is used to protect online transactions.
For implementation, changes to the operating system are necessary. The application does not require any changes.No modifications to the operating system are necessary for implementation; however, changes to the application are required.
IPsec is used to operate the system space.SSL is located in user space.


Authenticity, confidentiality, and message integrity are all guaranteed by the standard set of protocols known as IPsec, which is used to secure internet connections. Implementations don’t call for modifications to the upper-layer protocols or applications because it offers a transparent end-to-end encrypted channel. It is a mature protocol suite that supports a wide range of encryption and hashing algorithms, is exceedingly scalable, and is interoperable while having substantial drawbacks because of its complexity.

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