Pattern analysis of cipher text: A combined approach

Abstract

In this paper, we propose and implement a combined approach for identification of a given unknown sample of cipher text. In the first part of system, cipher text samples are generated randomly using different cipher algorithms. In the second part; the system analyses sample through a) Block Length/stream Detection b) Entropy/Reoccurrence Analysis c) Dictionary and Decision tree based approach. All these blocks analyzethe sample simultaneously. The block length/stream detection is done through counting the block length and by comparing to known sample's patterns. Whereas, the Entropy/reoccurrence analysis and Dictionary-Decision tree based approaches are done through the large data set characterization. At last, in the third part; the different block results are compared and result is generated. Finally, we analyze the system with unknown ciphertext samplesof AES, DES and Blow Fish, which is generated in random fashion and given as input to the system.