In this thesis we consider different problems related to provable security and indifferentiability framework. Ideal primitives such as random oracles, ideal ciphers are theoretical abstractions of cryptographic hash functions and block ciphers respectively. These idealized models help us to argue security guarantee for various cryptographic schemes, for which standard model security proofs are ...

Recently, methods from provable security, that had been developped for the last twenty years within the research community, have been extensively used to support emerging standards. This in turn has led researchers as well as practitioners to raise some concerns about this methodology. Should provable security be restricted to the standard computational model or can it rely on the so-called ran...

These lecture notes are a compilation of some of my readings while I was preparing two lectures given at EPFL on provable security in cryptography. They are essentially based on a book chapter from David Pointcheval called “Provable Security for Public Key Schemes” [24], on Victor Shoup’s tutorial on game playing techniques [30], on Coron’s Crypto’00 paper on the exact security of the Full Doma...

Virtualization is the mechanism that provides users a way to use many Operating Systems (OS) without need to reboot the system to shift one to another. If an adversary compromises any guest then virtual monitor (XEN in this context) has no reject any request from that OS. There is no formal proof that this virtual monitor provides security from them. We use virtualized system infrastructure of ...

The provable security paradigm originates from the work of Goldwasser and Micali [10] and plays a central role in modern cryptography. Since its inception, the focus of provable security has gradually shifted towards practice-oriented provable security [4]. The central goal of practice-oriented provable security is to develop and analyze efficient cryptographic systems that can be used for prac...

Abstract Recent lightweight hardware-based stream cipher designs keep an external non-volatile internal state that is not part of the cipher’s hardware module. The purpose these so-called small-state ciphers to size and power consumption low. We propose a random oracle model for ciphers. This will allow us analyse recent designs’ resistance against generic attacks and, in particular, time-memor...

We design and analyze a protocol for dividing a state into districts, where parties take turns proposing a division, and freezing a district from the other party’s proposed division. We show that our protocol has predictable and provable guarantees for both the number of districts in which each party has a majority of supporters, and the extent to which either party has the power to pack a spec...