Towards Parameterized Shared Key for AVK Approach

“Key” plays a vital role in every symmetric key cryptosystem. The obvious way of enhancing security of any cryptosystem is to keep the key as large as possible. But it may not be suitable for low power devices since higher computation will be done for longer keys and that will increase the power requirement which decreases the device's performance. In order to resolve the former specified problem an alternative approach can be used in which the length of key is fixed and its value varies in every session. This is Time Variant Key approach or Automatic Variable Key (AVK) approach. The Security of AVK based cryptosystem is enhanced by exchanging some parameters instead of keys between the communicating parties, then these parameters will be used to generate required keys at the receiver end. This chapter presents implementation of the above specified Mechanism. A model has been demonstrated with parameterized scheme and issues in AVK approach. Further, it has been analyzed from different users' perspectives. This chapter also highlights the benefits of AVK model to ensure two levels of security with characterization of methods for AVK and Estimation of key computation based on parameters only. The characteristic components of recent styles of key design with consideration of key size, life time of key and breaking threshold has also been pointed out. These characteristics are essential in the design of efficient symmetric key cryptosystem. The novel approach of AVK based cryptosystem is suitable for low power devices and useful for exchanging very large objects or files. This scheme has been demonstrated with Fibonacci-Q matrix and sparse matrix based diffused key information exchange procedures. These models have been further tested from perspective of hackers and cryptanalyst, to exploit any weakness with fixed size dynamic keys.