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Enhancement of Con�dentiality and Integrity using Cryptographic Techniques

Chandrasekharappa, T G S (2012) Enhancement of Con�dentiality and Integrity using Cryptographic Techniques. Phd. Thesis thesis, Manipal Institute of Technology, Manipal.

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Abstract

This dissertation addresses the issues pertaining to the development of a mod- i�ed Advanced Encryption Standard (AES) algorithm for a block cipher. The present AES algorithm uses a static S-box and Brute-force attack that needs to evaluate only 2128 keys. The one more threat facing by AES algorithm is the Extended Sparse Linearization attack, which is based on the framing a num- ber of algebraic equations between the input and the output values of each stage/block. Since the S-box is static now, breaking of the algorithm may be possible in future. But in the modi�ed AES algorithm the S- box is a dynamic one and is also a key dependent one. Since 21648 AES S-boxes are possible XSL attack becomes very di�cult. More over an AES box also contains MIX COL- UMN operation which is again static now. This MIX COLUMN is modi�ed as a dynamic one such that there are a large number of possible combinations for the MIX COLUMN matrix and has been made again a key dependent. By introducing these operations no extra memory is needed and the time required is negligible. While generating dynamic S-box it is found that some of the S-boxes giving maximum Avalanche Criteria. This important characteristic of S-boxes has also been addressed in detail. Using the dynamic S-box generation principle, a new key dependent stream cipher has been designed. This new stream cipher passes all the tests given by National Institute of Standards and Technology (NIST). The new stream cipher algorithm and the test results are also detailed. One more important aspect of the computer security is the Integrity of the data. In this dissertation the new HASH function generation based on the dynamic S-box have been discussed and the results have been found satisfactory.

Item Type: Thesis (Phd. Thesis)
Subjects: Engineering > MIT Manipal > Instrumentation and Control
Depositing User: MIT Library
Date Deposited: 24 Jun 2016 14:00
Last Modified: 24 Jun 2016 14:00
URI: http://eprints.manipal.edu/id/eprint/146415

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