Ivica Nikolic

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In this paper we construct a chosen-key distinguisher and a related-key attack on the full 256-bit key AES. We define a notion of differential q-multicollision and show that for AES-256 q-multicollisions can be constructed in time q · 2 and with negligible memory, while we prove that the same task for an ideal cipher of the same block size would require at(More)
While differential behavior of modern ciphers in a single secret key scenario is relatively well understood, and simple techniques for computation of security lower bounds are readily available, the security of modern block ciphers against related-key attacks is still very ad hoc. In this paper we make a first step towards provable security of block ciphers(More)
We propose the TWEAKEY framework with goal to unify the design of tweakable block ciphers and of block ciphers resistant to related-key attacks. Our framework is simple, extends the key-alternating construction, and allows to build a primitive with arbitrary tweak and key sizes, given the public round permutation (for instance, the AES round). Increasing(More)
In this article, we provide the first third-party security analysis of the PRINCE lightweight block cipher, and the underlying PRINCEcore. First, while no claim was made by the authors regarding related-key attacks, we show that one can attack the full cipher with only a single pair of related keys, and then reuse the same idea to derive an attack in the(More)
iii Abstract The National Institute of Standards and Technology (NIST) opened a public competition on November 2, 2007, to develop a new cryptographic hash algorithm – SHA-3, which will augment the hash algorithms specified in the Federal Information Processing Standard (FIPS) 180-4, Secure Hash Standard (SHS). The competition was NIST's response to(More)
In this paper we analyze the security of systems based on modular additions, rotations, and XORs (ARX systems). We provide both theoretical support for their security and practical cryptanalysis of real ARX primitives. We use a technique called rotational cryptanalysis, that is universal for the ARX systems and is quite efficient. We illustrate the method(More)
In this article we find collisions for step-reduced SHA-256. We develop a differential that holds with high probability if the message satisfies certain conditions. We solve the equations that arise from the conditions. Due to the carefully chosen differential and word differences, the message expansion of SHA-256 has little effect on spreading the(More)
In this paper we present known-plaintext single-key and chosenkey attacks on round-reduced LED-64 and LED-128. We show that with an application of the recently proposed slidex attacks [7], one immediately improves the complexity of the previous single-key 4-step attack on LED-128. Further, we explore the possibility of multicollisions and show single-key(More)
In this work, we introduce a new non-random property for hash/compression functions using the theory of higher order differentials. Based on this, we show a second-order differential collision for the compression function of SHA-256 reduced to 47 out of 64 steps with practical complexity. We have implemented the attack and provide an example. Our results(More)