Symmetric key cryptographic algorithms provide confidentiality, integrity, and authentication in modern communication systems. Our confidence in these algorithms is largely based on the fact that intense cryptanalysis has been carried out over several years without revealing any weakness. This thesis makes three independent contributions to the cryptanalysis of symmetric key primitives and hash...

Decorrelation Theory deals with general adversaries who are mounting iterated attacks, i.e., attacks in which an adversary is allowed to make d queries in each iteration with the aim of distinguishing a random cipher C from the ideal random cipher C∗. A bound for a non-adaptive iterated distinguisher of order d, who is making plaintext (resp. ciphertext) queries, against a 2d-decorrelated ciphe...

The stream ciphers Py, Pypy and Py6 were designed by Biham and Seberry for the ECRYPT-eSTREAM project in 2005. The ciphers were promoted to the ‘Focus’ ciphers of the Phase II of the eSTREAM project. However, due to some cryptanalytic results on the ciphers, strengthened versions of the ciphers, namely TPy, TPypy and TPy6 were built. So far there exists no attacks on TPy6. In this paper, we fin...

Among neurosteroids, allopregnanolone is the most potent endogenous positive modulator of GABA(A) receptors, and disturbances in its release may play a role in pathomechanism of some neurological and psychiatric disorders. In contrast to a large body of evidence on allopregnanolone involvement in pathogenesis of epilepsy, no data are available on its role in pseudoseizures. Therefore, the aim o...

Privacy-preserving collaborative filtering schemes are key recommender system technologies for e-commerce field. They focus on alleviating information overload problem by providing personalized recommendations without deeply jeopardizing customers’ privacy. Like their non-private versions, privacy-preserving recommendation methods might be easily subjected to profile injection attacks for manip...

We tested the effect of social isolation on the aggressiveness of an Amazonian fish: Astronotus ocellatus. Ten juvenile fishes were transferred from a group aquarium (60 x 60 x 40 cm) containing 15 individuals (without distinguishing sex) to an isolation aquarium (50 x 40 x 40 cm). Aggressiveness was tested by means of attacks on and displays toward the mirror image. The behavior was video-reco...

The Whirlwind hash function, which outputs a 512-bit digest, was designed by Barreto et al. and published by Design, Codes and Cryptography in 2010. In this paper, we provide a thorough cryptanalysis on Whirlwind. Firstly, we focus on security properties at the hash function level by presenting (second) preimage, collision and distinguishing attacks on reduced-round Whirlwind. In order to launc...

Abstract Neural-aided cryptanalysis is a challenging topic, in which the neural distinguisher ($\mathcal{ND}$) core module. In this paper, we propose new $\mathcal{ND}$ considering multiple ciphertext pairs simultaneously. Besides, are constructed from different keys. The motivation that distinguishing accuracy can be improved by exploiting features derived pairs. To verify motivation, have app...

The stream ciphers Py, Pypy and Py6 were designed by Biham and Seberry for the ECRYPT-eSTREAM project in 2005. The ciphers were promoted to the ‘Focus’ ciphers of the Phase II of the eSTREAM project. However, due to some cryptanalytic results on the ciphers, strengthened versions of the ciphers, namely TPy, TPypy and TPy6 were built. So far there exists no attacks on TPy6. In this paper, we fin...