An application running within an end-user’s Mobi session traverses multiple networks; the wireless access network, a wired transport and ISP network and ultimately the application’s destination network. Mobi enables security to be provided locally within each of these domains as well as end-to-end security.

The basic air interface security concept is that Security is both “horizontal” and “vertical”, and the Air interface provides encryption and authentication.

The basic security functions required in a communications network are:

1. Confidentiality to ensure that information is accessible only to authorized parties.
2. Authentication to minimize man-in-the-middle attacks.
3. Access control to ensure that only authorized users have access to the network.

Air-interface security
The key features of Mobi Air Interface Security are as follows:

• Authentication
  Mutual public key authentication of network and User Terminal that overcomes the problem of shared secret generation and exchange issues
  PKI mechanism ensures that only authorized base stations can obtain the keys and have access to the Mobi network.
• Encryption
  RC-4 stream cipher with up to 192 bit key.
  Secure IV updates & key diffusion for robustness: A new secret key is created each time a secure channel is established.
• Validation
  User authentication restricts access to the Mobi network.
  Information is verified against a RADIUS database, which stores user profile and information.

Network security
Different layers, network, transport and application, of security protocols are implemented in the Mobi system to enable and enforce end-to-end IP-centric security mechanism.

• Network layer security is achieved by using IP security standards such as IP Security (IPSec). IPSec is used to encrypt the L2TP tunnels that bear multiple user sessions between them.
  IPSec is used to provide end-to-end network layer security. In this case, the Mobi user’s end user device such as a Laptop supports an IPSec client and the ISP supports an IPSec gateway. All traffic between the Mobi user and the ISP is secured by an IPSec tunnel between the user Laptop and the IPSec gateway.
  IPSec can be used to secure business Virtual Private Networks over Mobi. IPSec forms the underpinning of most secure VPN solutions.
• Transport level security is achieved using Secure Socket Layer (SSL) and Transport Layer Security (TLS).
• Application level security is achieved by using PGP, Secure Shell (SSH) and Kerberos.