033

Title:

SMT-based Cube Attack on Simeck32/64

Discipline: Security and Privacy

Presenter:

Mojtaba Zaheri

Abstract:

Satisfiability modulo theories or SMT can be stated as a generalizationof Boolean satisfiability problem or SAT. The core idea behind the introductionof SMT solvers is to reduce the complexity through providing more informationabout the problem environment.In this paper, we take advantage of a similar idea and feed theSMT solveritself, by extra information provided through middle state Cube characteristics,to introduce a new method which we callSMT-based Cube Attack, and applyit to improve the success of the solver in attacking reduced-round versions of theSimeck32/64 lightweight block cipher.We first propose a new algorithm to find cubes with most number of middlestate characteristics. Then, we apply these obtained cubesand their characteristicsas extra information in the SMT definition of the cryptanalysis problem, to eval-uate its effectiveness. Our cryptanalysis results in a full keyrecovery attack by 64plaintext/ciphertext pairs on 12 rounds of the cipher in just 122.17 seconds. Thisis the first practical attack so far presented against the reduced-round versions ofSimeck32/64.We also conduct the cube attack on the Simeck32/64 to compare with theSMT-based cube attack. The results indicate that the proposed attack is morepowerful than the cube attack.

Author(s):

Mojtaba Zaheri, Babak Sadeghiyan

Funding Acknowledgements:

AUT