Define Internet Security, IP Security (IPSec) and Secure Socket Layer(SSL)

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English: Encapsulating one IP packet in anothe...
English: Encapsulating one IP packet in another IP packet (Photo credit: Wikipedia)
Internet Security is the securing web server and client (browser) from the possible attacks over the Wide Area Networks or Internet. Internet security is a type of Computer Security or the network Security. It includes mainly specific security protocols like IPSec (Internet Security Protocol), SSL (Secure Socket Layer) or TSL (Transport Layer Security). Internet Security also describes about PGP (Pretty Good Privacy) which is designed to create authenticated and confidential e-mails. It also discuss about Firewalls and Antivirus Programs.

IP Security (IPSec)


IP Security (IPSec) is collection of protocols designed by Internet Engineering Task Force (IETF) to provide security for a packet at the network level. It helps to create authenticated and confidential packets for the IP layer. IPSec operates in one of the following two modes.

i) Transport Mode


In this mode, IPSec protects what is delivered from the transport layer to the network layer. i.e. the transport mode protects the network layer payload, the payload to be encapsulated in the network layer. This mode does not protect the IP header, i.e. it protects only the packet from the transport layer. In this mode, the IPSec header and trailer are added to the information coming from the transport layer. The IP header is added later. This mode is normally used when we need host-to-host protection of data. The sending host uses IPSec to authenticate and / or encrypt the payload delivered from the transport layer. The receiving host uses IPSec to check the authentication and / or decrypt the IP Packet and deliver it to the transport layer.

ii) Tunnel Mode

  Internet Security & IP Security


Tunneling or encapsulation is a common technique in packet-switched networks. It consists of wrapping a packet in a new one. That is, a new header is attached to the original packet. The entire original packet becomes the payload of the new one, as shown in Figure. In this mode, IPSec protects the entire IP Packet. It takes an IP packet including the header, applies IPSec security methods to the entire Packet, and then adds a new IP header. The new IP header has different information than the original IP Header.

In general, tunneling is used to carry traffic of one protocol over a network that does not support that protocol directly. For example, NetBIOS or IPX can be encapsulated in IP to carry it over a TCP/IP WAN link. In the case of IPSec, IP is tunneled through IP for a slightly different purpose: To provide total protection, including the header of the encapsulated Packet. Tunneling requires intermediate processing of the original packet while en-route. The destination specified in the outer header, usually and IPSec firewall of router, receives the tunneled packet, extracts the original packet, and sends it to the ultimate destination. The processing cost is compensated by the extra security. A notable advantage of IP tunneling is the possibility to exchange packets with private IP addresses between two intranets over the public Internet, which requires globally unique addresses.


The IPsec framework has three main components, Authentication Header(AH), Encapsulating Security Payload (ESP) and Internet Key Exchange (IKE).

Authentication Header (AH)


AH is used to provide integrity and authentication of IP datagrams. Replay protection is also possible. Although its usage is optional, the replay protection service must be implemented by any IPsec compliant system. The services are connectionless, they work on a per-packet basis. AH is used in two modes, transport mode and tunnel mode.

Encapsulating Security Payload (ESP)

English: IP packet with IPsec ESP
English: IP packet with IPsec ESP  (Photo credit: Wikipedia)
ESP is used to provide integrity check, authentication and encryption to IP datagrams. Optional replay protection is also possible. These services are connectionless, in that they operate on a per-packet basis. Encryption can be selected independently of other services. It is highly recommended that, if encryption is enabled, integrity check and authentication be turned on. Like AH, ESP can be used in two ways: Transport mode and tunnel mode.

Internet Key Exchange Protocol (IKE)


The internet Key Exchange (IKE) framework, previously referred to as ISAKMP/Oakley, supports automated negotiation of security Associations, and automated generation and refresh of cryptographic keys. The ability to perform these functions with little or no manual configuration of machines is a critical element to any enterprise-scale IPsec deployment. Internet security association and key management protocol (ISAKMP) is a framework that defines the management of security associations (negotiable, modify, delete) and keys, and it also defines the payloads for exchanging key generation and authentication data. Internet Key exchange (IKE) is a protocol that uses parts of ISAKMP and the Oakley and SKEME key exchange protocols to provide management of keys and security associations for the IPsec AH and ESP protocols and ISAKMP itself.

Secure Socket Layer (SSL)



Secure Socket Layer (SSL) is a security protocol that was developed by Netscape Communications Corporation, along with RSA Data Security, Inc. The Primary goal of the SSL protocol is to provide a private channel between communicating applications, which ensures privacy of data, authentication of the partners, and integrity. The Secure Socket Layer (SSL) technology was used for the websites or web applications which need more security.


Schematic representation of the SSL handshake ...
 SSL handshake protocol with two way authentication with certificates. (Photo credit: Wikipedia)

Secure Socket Layer (SSL) is composed of two layers:


  • At the lower layer, a protocol for transferring data using a variety of predefined cipher and authentication combinations, called the SSL Record Protocol.
  • On the upper layer, a protocol for initial authentication and transfer of encryption keys, called the SSL Handshake Protocol.

An SSL session is initiated as follows:


  • On the client (browser), the user requests a document with a special URL that starts with https: instead of http: either by typing it into the URL input field, or by clicking the link. For example the major search engines like Google, Yahoo, Bing and other money transactions websites uses Secure Socket Layer (SSL).The client computers which do not installed the Secure Socket Layer (SSL) certificates on their computer unable to browse those sites.
  • The client code recognizes the SSL request and establishes a connection through TCP port 443 to the SSL code on the server.
  • The client then initiates the SSL handshake phase, using the SSL Record Protocol as a carrier. At this point, there is no encryption or integrity checking built into the connection.

The Secure Socket Layer (SSL) Protocol addresses the following security issues:


  • Privacy: After the symmetric key is established in the initial handshake, the messages are encrypted using this key.
  • Integrity: Messages contain a message authentication code (MAC) ensuring the message integrity.
  • Authentication: During the handshake, the client authenticates the server using an asymmetric or public key. It can also be based on certificates. SSL requires that each message is encrypted and decrypted and therefore has a high performance and resource cost.

Secure Socket Layer (SSL) Protocol


The SSL protocol is located at the top of the transport layer. SSL is also a layered protocol itself. It simply takes the data from the application layer, re-formats it, and transmits it to the transport layer. SSL handles a message as follows.

The sender performs the following tasks

  • Takes the message from upper layer.
  • Fragments the data to manageable blocks.
  • Optionally compress the data.
  • Applies a message authentication code (MAC)
  • Encrypts the data.
  • Transmits the result to the lower layer.

 The receiver performs the following tasks.


  • Takes the data from lower layer.
  • Decrypts.
  • Verifies the data with the negotiated MAC key.
  • Decompress the data if compression was used.
  • Reassembles the message.
  • Transmits the message to the upper layer.


An SSL session works in different states. These states are session and connection states. The SSL handshake protocol coordinates the states of the client and the server. In addition, there are read and write states defined to coordinate the encryption according to the change Cipher Spec messages.

Change Cipher Spec Protocol


The change Cipher Spec protocol is responsible for sending change Cipher Spec messages. At any time, the client can request to change current cryptographic parameters such as the handshake key exchange. Following the change Cipher Spec notification, the client sends a handshake key exchange and if available, certificate verify messages, and the server sends a change Cipher Spec message after processing the key exchange message. After that, the newly agreed keys will be used until the next change Cipher Spec request. The change Cipher Spec message is sent after the hello messages during the negotiation.

SSL handshake protocol


The SSL handshake protocol allows the client and server to determine the required parameters for and SSL connection such as protocol version, cryptographic algorithms, optional client or server authentication, and public key encryption methods to generate shared secrets. During this process, all handshake messages are forwarded to the SSL record layer to be encapsulated into special SSL messages. Figure below illustrates an SSL handshake process.


Secure Socket Layer (SSL)


SSL record protocol


After the master key has been determined, the client and server can use it to encrypt application data. The SSL record protocol specifies a format for these messages in general, they include a message digest ensure that they have not been altered and the whole message is encrypted using a symmetric cipher.


Other Internet security methods are: Transport Layer Security (TSL), Pretty Good Privacy (PGP) and Firewall, I will post about them later. Keep following this blog.