Cryptography, Volume 2, Issue 2 (June 2018) – 5 articles

This article presents a sequential domain extension scheme with minimum padding for hashing using a compression function. The proposed domain extension scheme is free from the length extension property. The collision resistance of a hash function using the proposed domain extension is shown to be reduced to the collision resistance and the everywhere preimage resistance of the underlying compression function in the standard model, where the compression function is assumed to be chosen at random from a function family in some efficient way. Its indifferentiability from a random oracle up to the birthday bound is also shown on the assumption that the underlying compression function is a fixed-input-length random oracle or the Davies-Meyer mode of a block cipher chosen uniformly at random. The proposed domain extension is also applied to the sponge construction and the resultant hash function is shown to be indifferentiable from a random oracle up to the birthday bound in the ideal permutation model. The proposed domain extension scheme is expected to be useful for processing short messages. Full article

This paper presents a method for a decentralised peer-to-peer software license validation system using cryptocurrency blockchain technology to ameliorate software piracy, and to provide a mechanism for software developers to protect copyrighted works. Protecting software copyright has been an issue since the late 1970s and software license validation has been a primary method employed in an attempt to minimise software piracy and protect software copyright. The method described creates an ecosystem in which the rights and privileges of participants are observed. Full article

We study characterizations of one-way functions in terms of time-bounded Kolmogorov complexity. As the main contribution, we propose definitions for strong and weak Kolmogorov one-way functions and show that these are equivalent to classical strong and weak one-way functions, respectively. The new definitions were motivated by the fact that the expected value approach is not able to characterize strong one-way functions as we prove in the paper. Full article

We consider an authentication process that makes use of biometric data or the output of a physical unclonable function (PUF), respectively, from an information theoretical point of view. We analyse different definitions of achievability for the authentication model. For the secrecy of the key generated for authentication, these definitions differ in their requirements. In the first work on PUF based authentication, weak secrecy has been used and the corresponding capacity regions have been characterized. The disadvantages of weak secrecy are well known. The ultimate performance criteria for the key are perfect secrecy together with uniform distribution of the key. We derive the corresponding capacity region. We show that, for perfect secrecy and uniform distribution of the key, we can achieve the same rates as for weak secrecy together with a weaker requirement on the distribution of the key. In the classical works on PUF based authentication, it is assumed that the source statistics are known perfectly. This requirement is rarely met in applications. That is why the model is generalized to a compound model, taking into account source uncertainty. We also derive the capacity region for the compound model requiring perfect secrecy. Additionally, we consider results for secure storage using a biometric or PUF source that follow directly from the results for authentication. We also generalize known results for this problem by weakening the assumption concerning the distribution of the data that shall be stored. This allows us to combine source compression and secure storage. Full article

Recent developments have increased the demand for adequate security solutions, based on primitives that cannot be easily manipulated or altered, such as hardware-based primitives. Security primitives based on Dynamic Random Access Memory (DRAM) can provide cost-efficient and practical security solutions, especially for resource-constrained devices, such as hardware used in the Internet of Things (IoT), as DRAMs are an intrinsic part of most contemporary computer systems. In this work, we present a comprehensive overview of the literature regarding DRAM-based security primitives and an extended classification of it, based on a number of different criteria. In particular, first, we demonstrate the way in which DRAMs work and present the characteristics being exploited for the implementation of security primitives. Then, we introduce the primitives that can be implemented using DRAM, namely Physical Unclonable Functions (PUFs) and True Random Number Generators (TRNGs), and present the applications of each of the two types of DRAM-based security primitives. We additionally proceed to assess the security such primitives can provide, by discussing potential attacks and defences, as well as the proposed security metrics. Subsequently, we also compare these primitives to other hardware-based security primitives, noting their advantages and shortcomings, and proceed to demonstrate their potential for commercial adoption. Finally, we analyse our classification methodology, by reviewing the criteria employed in our classification and examining their significance. Full article