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Side channel cryptanalysis has received significant attention lately, because it provides a low-cost and facile way to reveal the secret information held on a secure computing system. One particular type of side channel attacks, called cache-based side channel attacks, aims to deduce information about the state of a cryptographic algorithm or its key by observing the data-dependent behavior of a microprocessor's cache memory. These attacks have been proven successful and very hard to protect against. In this paper, we introduce the use of the Cache Decay approach as an aid to guard against cache-based side channel attacks. Cache Decay controls the lifetime (called decay interval) of the cache items and was initially proposed for cache power leakage savings. By randomly selecting the decay interval of the cache, we actually create caches with non-deterministic behavior in regard to their statistics. Thus, as we demonstrate, multiple runs of the same algorithm (performing on the same input) will result in different cache statistics, defending against the attacker and reinforcing the protection offered by the system. In our work, we use a cycle-based processor simulator, enhanced with the required modifications, in order to evaluate our proposal and show that our technique can be used effectively to protect against cache-based side channel attacks.

Purpose -During steel plate and long-product production, numerous imperfections and defects appear that deteriorate product quality and consequently reduce revenue. The purpose of this paper is to provide a practical overview of typical defects (surface and internal) that occur and their root causes. Design/methodology/approach -The data presented here derive from the quality department and from more than 50 technical reports of ELKEME S.A. on the last decade's production of steel making companies STOMANA S.A. and SIDENOR S.A., with emphasis on the defects occurred in some of the products of the Bulgarian plant. Stereoscopic observations of surface defects, light optical metallography, and scanning electron microscopy with EDS represent the most used techniques to characterize defected macro-/micro-areas and microstructures. Findings -In general, the most commonly encountered defects from semi-finished (billets, blooms, and slabs) and final (round bar and plate) steel products are as follows: network cracks, porosity, gas holes, shrinkage, shell, slivers, casting powder entrapment, ladle slag entrapment, other non-metallic inclusions, low hot ductility, centerline segregation cracking, macro-and micro-segregation, and mechanical defects (scratches, transverse cracks, and seams). Practical implications -External and internal quality improvement can reduce the production cost (Euro/ton). Social implications -Improvement of the quality of industrial plates and long products increases the safety of the further-produced constructions and systems such as bridges, cranes, heavy equipment, automobile parts, etc. Originality/value -Root cause analysis and categorization of the most commonly encountered defects can pave the way to production process improvements that directly affect final product quality and the overall per ton production cost. The benefits of this work obviously affect all steel producers/ processers, and also society through the safety increase achieved by the quality improvement in the steel products used in constructions and automobile parts.

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