Part 1: IP Security (IPSEC) Story

Today we are going to talk about IPSEC. As many of you already knew about that IPSEC stands for IP Security and is the way of creating the tunnel from source to destination when the medium is internet in between. A lot of vendors are using IPSEC in their environment for the secure traffic over an untrusted network which is internet.

IPSEC uses encryption, Integrity, Authentication and Anti-replay.

Fig 1.1- IPSEC over Internet

Encryption: 
Well as you know that it is very important to encrypt the data when you are sending the traffic through the internet as data sent in clear text over the internet can easily be intercepted and stolen.

What IPSEC do for Encryption?
IPSEC generally uses Keys for encryption which may be a symmetric or Asymmetric keys. IPSEC uses keys for encrypt and decrypt data

General approach is to use the Asymmetric keys which actually requires two different keys for encrypt and decrypt data. The name is like encryption is with the public key and decryption is with the private key while in symmetric both encrypt and decrypt keys are same.

We will talk about the Keys in more detail where we will discuss on DES, 3DES, AES or Blowfish encryption algorithms.

Data Integrity: 
The second most important factor in IPSEC is Data Integrity because we want the same data which we sent from the source to the destination and on the internet, the data can be manipulated. 

What IPSEC do for Data Integrity?
IPsec uses hashing algorithm to check the integrity of the data received. If the hash values are different you will easily understand that data is manipulated. IPSEC uses HMAC and utilizes a secret key when computing the hash value, thus preventing an attacker from altering the packet and then re-computing the correct hash. 

Authentication: 
The third most important factor in IPSEC is Authentication. For an IPSEC VPN tunnel to be established, both sides of the tunnel must be authenticated. To accomplish this, either pre-shared keys or RSA digital signatures are used.

IPSEC protocol headers
IPsec uses two types of protocol headers and they are Authentication Header (AH) and Encapsulation Security Payload (ESP) 

We will discuss on the difference between Authentication Header (AH) and Encapsulation Security Payload (ESP) in our Part 2 article and will further discuss on IPSEC modes, Internet Key Exchange (IKE). Stay connected.