Document Type : Research Article
1 Faculty and Research Center of Communication and Information Technology, Imam Hossein University, Tehran, Iran.
2 Information Systems and Security Lab (ISSL), Sharif University of Technology, Tehran, Iran.
3 The Electrical Engineering Department of Shahid Rajaee Teachers Training University, Tehran, Iran.
4 Department of Mathematics, Faculty of Science, University of Qom, Qom, Iran.
ΑΕS _ CMCCv₁, ΑVΑLΑNCHEv₁, CLΟCv₁, and SILCv₁ are four candidates of the first round of CAESAR. CLΟCv₁ is presented in FSE 2014 and SILCv₁ is designed upon it with the aim of optimizing the hardware implementation cost. In this paper, structural weaknesses of these candidates are studied. We present distinguishing attacks against ΑES _ CMCCv₁ with the complexity of two queries and the success probability of almost 1, and distinguishing attacks on CLΟCv₁ and SILCv₁ with the complexity of Ο (2n/2) queries and the success probability of 0.63, in which n is bit length of message blocks. In addition, a forgery attack is presented against ΑVΑLΑNCHEv₁ which requires only one query and has the success probability of 1. The attacks reveal weaknesses in the structure of these first round candidates and inaccuracy of their security claims.