Paper 2021/209

Sampling methods for cryptographic tests

George Marinakis

Abstract

Abstract Modern cryptographic algorithms have an enormous key diversity, so if we want to test their strength for all the keys, it will take practically an infinite time. To avoid this, we use the sampling method, in which we examine a much smaller number of keys n and then we make estimation for the total key population N with a predetermined sampling error. For the generation of the n cipher outputs (samples) with the n corresponding keys, the critical questions are how many samples we will test and how large must be the size of each sample. The general rule is that, the sampling error is reduced as we increase the number of the samples. But since the tests must be executed in an acceptable time, we must compromise the above rule with some additional factors, such as the type of the cryptographic cipher, the kind and the size of the plain information and of course the available computer power. In this study we examine the interrelations of all the above factors, and we propose applicable solutions. Keywords: Cryptography, Data encryption, Communication security, Computer security, Data security, Information security.

Note: George Marinakis holds a MS in Electrical Engineering from University of Patras (Greece) and a PhD in Cryptography from National Technical University of Athens (NTUA). He is a former professor at Telecommunications and Electronics School of Signal Officers (Athens, Greece). He is currently instructor and scientific collaborator at Hellenic Army Academy. He can be reached at gmari@tee.gr.