www.cryptoplexity.de oezguer.dagdelen @ cased.de marc.fischlin @ gmail.com tommaso @ gagliardoni.net Abstract. The Fiat-Shamir transformation is a famous technique to turn identification schemes into signature schemes. The derived scheme is provably secure in the random-oracle model against

factor of Õ(n2) in the standard model, while the security of the signature scheme is based on the same assumption in the random oracle model. Our protocols are very efficient, with all operations requiring Õ(n) time. We also show that the technique for constructing our lattice-based schemes can be used

of security. These heuristics are typically very efficient and are believed to be secure, though no proof of security has been provided. In this thesis we study the security of two types of such popular heuristics: (1) the Fiat-Shamir paradigm for constructing digital signature schemes, and (2) heuristics

of statistical queries and correlating the responses. Statlstmal data banks are much less secure than most people beheve. Data encryption attempts to prevent unauthorized disclosure of confidential information in transit or m storage. This paper describes the general nature of controls of each type, the kinds

Current standard security practices do not provide substantial assurance that the end-to-end behavior of a computing system satisfies important security policies such as confidentiality. An end-to-end confidentiality policy might assert that secret input data cannot be inferred by an attacker

incorporating a random seed into the Fiat-Shamir transform so that the commitment space assumption may be removed. Keywords: Signature schemes, identification schemes, Fiat-Shamir transform, forward security,

signature. Other implementations can be broken using a larger number of erroneous signatures. We also analyze the vulnerability to hardware faults of two identification protocols: Fiat-Shamir and Schnorr. The Fiat-Shamir protocol can be broken after a small number of erroneous executions of the protocol

incorporating a random seed into the Fiat-Shamir transform so that the commitment space assumption may be removed. Keywords: Signature schemes, identification schemes, Fiat-Shamir transform, forward security,

A model of a real-time intrusion-detection expert system capable of detecting break-ins, penetrations, and other forms of computer abuse is described. The model is based on the hypothesis that security violations can be detected by monitoring a system's audit records for abnormal patterns

The notion of non-malleable cryptography, an extension of semantically secure cryptography, is defined. Informally, in the context of encryption the additional requirement is that given the ciphertext it is impossible to generate a different ciphertext so that the respective plaintexts are related