IPSEC

TCP/IP is a set of communication protocol used for communication between the information system. In this TCP/IP communication, IPsec is one of the protocol that can be used to initiate a secure and authenticated communication between the interconnected systems. It mainly operates in L3 of the OSI model. There are other protocols like TLS/SSL providing the same authenticated and secure communication between the interconnected systems.

IPsec Details : IPsec basically consists of two protocols and two operation modes

• Protocols:

1. Authentication Header (AH): AH is a protocol in IPsec which provides authenticity and integrity for the payload not for the headers, however it will not provide any confidentiality.
2. Encapsulation Security Protocol (ESP): ESP is another protocol in IPsec which provides authenticity and confidentiality for both the IP payloads and headers.

• Operating Modes

1. Transport Mode: The transport mode in IPsec provides authentication and confidentiality only to the IP payloads/ data
2. Tunnel Mode: The tunnel mode in IPsec provides authentication and confidentiality for the IP payload's and headers using both AH and ESP

IKE

IKE is another concept in IPsec and it's known as the internet key exchange. These are the protocols in the IPsec suite which provides the authenticity and secure communication. IKE uses X509 certificates for the authenticity and Diffie-Hellman algorithm for the key exchange and symmetric key generation. IKE consists of 2 versions, IKEv1 and IKEv2.

Remote Access

Secure remote access can be established using VPN, SSH, SFTP, PPP. If we use VPN, the same can be configured using IPsec/ SSL.

• IPsec VPN

The IPsec VPN communication happens in two phases 1. IKE Phase1 and IKE Phase 2

Both the phases has been diagrammatically represented below: