Usually, a proof of a theorem contains more knowledge than the mere fact that the theorem is true. For instance, to prove that a graph is Hamiltonian it suffices to exhibit a Hamiltonian tour in it; however, this seems to contain more knowledge than the single bit Hamiltonian/non-Hamiltonian.In this paper a computational complexity theory of the “knowledge” contained in a proof is developed. Zero-knowledge proofs are defined as those proofs that convey no additional knowledge other than the correctness of the proposition in question. Examples of zero-knowledge proof systems are given for the languages of quadratic residuosity and 'quadratic nonresiduosity. These are the first examples of zero-knowledge proofs for languages not known to be efficiently recognizable.

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The knowledge complexity of interactive proof-systems

In this paper, we define and explore proofs of retrievability (PORs). A POR scheme enables an archive or back-up service (prover) to produce a concise proof that a user (verifier) can retrieve a target file F, that is, that the archive retains and reliably transmits file data sufficient for the user to recover F in its entirety.A POR may be viewed as a kind of cryptographic proof of knowledge (POK), but one specially designed to handle a large file (or bitstring) F. We explore POR protocols here in which the communication costs, number of memory accesses for the prover, and storage requirements of the user (verifier) are small parameters essentially independent of the length of F. In addition to proposing new, practical POR constructions, we explore implementation considerations and optimizations that bear on previously explored, related schemes.In a POR, unlike a POK, neither the prover nor the verifier need actually have knowledge of F. PORs give rise to a new and unusual security definition whose formulation is another contribution of our work.We view PORs as an important tool for semi-trusted online archives. Existing cryptographic techniques help users ensure the privacy and integrity of files they retrieve. It is also natural, however, for users to want to verify that archives do not delete or modify files prior to retrieval. The goal of a POR is to accomplish these checks without users having to download the files themselves. A POR can also provide quality-of-service guarantees, i.e., show that a file is retrievable within a certain time bound.

PORs: Proofs of Retrievability for Large Files

A new 1D chaotic system for image encryption

2D Sine Logistic modulation map for image encryption

A new color image encryption using combination of the 1D chaotic map

Cryptanalysis of a one round chaos-based Substitution Permutation Network

A formal methodology for integral security design and verification of network protocols

Moodle is one of the most popular open source e-learning platforms. It makes available a very easy-to-deploy environment, which once installed, is ready to be used. These two characteristics, make it a very attractive choice. But regarding information security and privacy, it presents several and important drawbacks. This is mainly due to the fact that it leaves the most serious tasks, like server configuration or access control in the hands of the system administrator or third-party module developers. This approach is understandable, as is that very fact what makes Moodle easy and therefore attractive. The aim of this paper is not to discredit this option, but to enhance it by means of standard cryptographic and information security infrastructures. We focus in the registration process, which ends with the distribution of a user certificate. To link the users' real identity with their virtual one, we have taken an approach that merges EBIAS (Email Based Identification and Authentication System) with a kind of challenge-response method involving secure pseudo random number generation based in a fast chaos-based Pseudo Random Number Generator.

An approach for adapting moodle into a secure infrastructure

New X.509-based mechanisms for fair anonymity management

The current technological scenario determines a profileration of trust domains, which are usually defined by validating the digital identity linked to each user. This validation entails critical assumptions about the way users’ privacy is handled, and this calls for new methods to construct and treat digital identities. Considering cryptography, identity management has been constructed and managed through conventional digital signatures. Nowadays, new types of digital signatures are required, and this transition should be guided by rigorous evaluation of the theoretical basis, but also by the selection of properly verified software means. This latter point is the core of this paper. We analyse the main non-conventional digital signatures that could endorse an adequate tradeoff between security and privacy. This discussion is focused on practical software solutions that are already implemented and available online. The goal is to help security system designers to discern identity management functionalities through standard cryptographic software libraries.

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Jesus Diaz

Papers

Cryptanalysis of a one round chaos-based Substitution Permutation Network

A formal methodology for integral security design and verification of network protocols

An approach for adapting moodle into a secure infrastructure

New X.509-based mechanisms for fair anonymity management

Non-conventional digital signatures and their implementations – A review