A tutorial introduction to CryptHOL

This tutorial demonstrates how cryptographic security notions, constructions, and game-based security proofs can be formalized using the CryptHOL framework. As a running example, we formalize a variant of the hash-based ElGamal encryption scheme and its IND-CPA security in the random oracle model. This tutorial assumes familiarity with Isabelle/HOL basics and standard cryptographic terminology

On the Existence of the Logarithmic Correction Term in Black Hole Entropy-Area Relation

In this paper we consider a model universe with large extra dimensions to obtain a modified black hole entropy-area relation. We use the generalized uncertainty principle to find a relation between the number of spacetime dimensions and the presence or vanishing of logarithmic prefactor in the black hole entropy-area relation. Our calculations are restricted to the microcanonical ensembles and we show that in the modified entropy-area relation, the microcanonical logarithmic prefactor appears only when spacetime has an even number of dimensions.Comment: 9 Pages, No Figure

Formal Verification of Composable Security Proofs

Computer-aided cryptography improves the rigor of security proofs by mechanizing their verification. Existing formal-methods tools focus primarily on the game-based paradigm, and the results on formalizing simulation-based proofs are limited. Simulation-based frameworks are popular since they support the composition of security proofs, but the level of details in these frameworks surpasses what the formal-methods community can reasonably handle with state-of-the-art techniques. Hence, existing formal results consider streamlined versions of simulation-based frameworks to cope with their complexity. Recent advancements in cryptography frameworks enable the development of better tools for formalizing composable security proofs. Constructive Cryptography is a generic theory allowing for clean, composable security statements that empowers protocol designers to focus on a particular aspect of security proofs without being distracted by other details. It lays the foundation for formal-methods tools that support mechanized verification of composable security statements. In this thesis, we formalize an instance of Constructive Cryptography. Our approach is suitable for mechanized verification and we use CryptHOL, a framework for developing mechanized cryptography proofs, to implement it in the Isabelle/HOL theorem prover. We extend CryptHOL with an abstract model of Random Systems and provide proof rules for their equality and composition. We then formalize security as a special kind of random system construction in which a complex system is built from simpler ones. We demonstrate the practicality of our approach by formalizing two different constructions of a secure channel. Our formal approach enables us to delve into an aspect of composable security proofs that has not been considered in previous formal results: we highlight the importance of system communication modeling in composable security statements. We show that fixing the communication patterns, which is sometimes applied to simplify proofs and overcome their complexity, can affect the reusability of security statements. We propose an abstract approach to modeling systems communication in Constructive Cryptography that avoids this problem

CryptHOL: Game-Based Proofs in Higher-Order Logic

ISSN:1432-1378ISSN:0933-279

The Comparison of Antifungal Effects of Methylene Chloride and Methanol Extracts of Green and Black Tea on Candida Albicans

BACKGROUND AND OBJECTIVE: Background: Candidiasis is the most common fungal infection. Nystatin is often used to treating of candidiasis that creates the problem of drug resistance and side effects. Study was performed to determine the antifungal properties of black and green tea extracts against Candida albicans. METHODS: To do this basic study, at first methylene chloride and methanolic extracts of green and black tea were prepared. Disk diffusion method and measuring the diameter of inhibition zone was used to determine anti-fungal extracts against Candida albicans. The methanolic extract at doses of 2, 4, 6, 8 and 10 mg and methylene chloride extracts with concentrations of 0.2, 0.4, 0.6, 0.8 and 1 mg per disk were used and the results compared in 24 and 48 hours. FINDINGS: Methylene chloride extracts of both type of tea create antifungal activity more than methanol extracts. The maximum antifungal activity 24 hours by a concentration of 1 mg hard methylene chloride extract was obtained and in this concentration with formation of zone inhibition 30.57±4.4 and 34.25±2.7 mm, respectively, for the methylene chloride extract of green tea and black more antifungal effect compared to Nystatin (20±1.06 mm) was established (p<0.01). CONCLUSION: The results have shown that green and black tea leaf extract can create antifungal activity effects against Candida albicans as dose -dependent manner and is more effective in the first 24 hours than the 48 hours <xm </x