Search results for "Crypt"
showing 10 items of 1111 documents
Understanding Quantum Algorithms via Query Complexity
2017
Query complexity is a model of computation in which we have to compute a function $f(x_1, \ldots, x_N)$ of variables $x_i$ which can be accessed via queries. The complexity of an algorithm is measured by the number of queries that it makes. Query complexity is widely used for studying quantum algorithms, for two reasons. First, it includes many of the known quantum algorithms (including Grover's quantum search and a key subroutine of Shor's factoring algorithm). Second, one can prove lower bounds on the query complexity, bounding the possible quantum advantage. In the last few years, there have been major advances on several longstanding problems in the query complexity. In this talk, we su…
If P≠NP then some strongly noninvertible functions are invertible
2006
AbstractRabi, Rivest, and Sherman alter the standard notion of noninvertibility to a new notion they call strong noninvertibility, and show—via explicit cryptographic protocols for secret-key agreement (Rabi and Sherman attribute this protocol to Rivest and Sherman) and digital signatures (Rabi and Sherman)—that strongly noninvertible functions are very useful components in protocol design. Their definition of strong noninvertibility has a small twist (“respecting the argument given”) that is needed to ensure cryptographic usefulness. In this paper, we show that this small twist has a consequence: unless P=NP, some strongly noninvertible functions are invertible.
A Generalization of Girod’s Bidirectional Decoding Method to Codes with a Finite Deciphering Delay
2012
In this paper we generalize an encoding method due to Girod (cf. [6]) using prefix codes, that allows a bidirectional decoding of the encoded messages. In particular we generalize it to any finite alphabet A, to any operation defined on A, to any code with finite deciphering delay and to any key x ∈ A+ , on a length depending on the deciphering delay. We moreover define, as in [4], a deterministic transducer for such generalized method. We prove that, fixed a code X ∈ A* with finite deciphering delay and a key x ∈ A *, the transducers associated to different operations are isomorphic as unlabelled graphs. We also prove that, for a fixed code X with finite deciphering delay, transducers asso…
Nonmalleable encryption of quantum information
2008
We introduce the notion of "non-malleability" of a quantum state encryption scheme (in dimension d): in addition to the requirement that an adversary cannot learn information about the state, here we demand that no controlled modification of the encrypted state can be effected. We show that such a scheme is equivalent to a "unitary 2-design" [Dankert et al.], as opposed to normal encryption which is a unitary 1-design. Our other main results include a new proof of the lower bound of (d^2-1)^2+1 on the number of unitaries in a 2-design [Gross et al.], which lends itself to a generalization to approximate 2-design. Furthermore, while in prime power dimension there is a unitary 2-design with =…
Real-space grids and the Octopus code as tools for the development of new simulation approaches for electronic systems.
2015
This Open Access Article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
HybridS: A Scheme for Secure Distributed Data Storage in WSNs
2008
In unattended wireless sensor networks (WSNs), data is stored locally or at designated nodes upon sensing, and users can access it on demand. This paradigm can improve energy efficiency by making use of the upcoming cheap and large flash memory, as well as system robustness. Nevertheless, the security and dependability of distributed storage are critical for the applicability of such WSNs. In this paper, we propose a secure and dependable data storage scheme by taking advantages of secret sharing and Reed-Solomon code, which has computational security and yet maintains optimal data size. The extensive analysis verifies our scheme can provide secure and dependable data storage in WSNs in the…
Requirements for XML document database systems
2001
The shift from SGML to XML has created new demands for managing structured documents. Many XML documents will be transient representations for the purpose of data exchange between different types of applications, but there will also be a need for effective means to manage persistent XML data as a database. In this paper we explore requirements for an XML database management system. The purpose of the paper is not to suggest a single type of system covering all necessary features. Instead the purpose is to initiate discussion of the requirements arising from document collections, to offer a context in which to evaluate current and future solutions, and to encourage the development of proper …
Ontology-based integration of XML data: Schematic marks as a bridge between syntax and semantic level
2007
This paper presents an ontology integration approach of XML data. The approach is composed of two pillars the first of which is based on formal language and XML grammars analysis. The second pillar is based on ontology and domain ontology analysis. The keystone of this architecture which creates a bridge between the two pillars is based on the concept of schematic marks introduced in this paper. These schematic marks make it possible to establish the link between the syntactic level and the semantic level for our integration framework.
XML document-grammar comparison: related problems and applications
2011
10.2478/s13537-011-0005-1; International audience; XML document comparison is becoming an ever more popular research issue due to the increasingly abundant use of XML. Likewise, a growing interest fosters the development of XML grammar matching and comparison, due to the proliferation of heterogeneous XML data sources, particularly on the Web. Nonetheless, the process of comparing XML documents with XML grammars, i.e., XML document and grammar similarity evaluation, has not yet received the attention it deserves. In this paper, we provide an overview on existing research related to XML document/grammar comparison, presenting the background and discussing the various techniques related to th…
Extensible User-Based XML Grammar Matching
2009
International audience; XML grammar matching has found considerable interest recently due to the growing number of heterogeneous XML documents on the web and the increasing need to integrate, and consequently search and retrieve XML data originated from different data sources. In this paper, we provide an approach for automatic XML grammar matching and comparison aiming to minimize the amount of user effort required to perform the match task. We propose an open framework based on the concept of tree edit distance, integrating different matching criterions so as to capture XML grammar element semantic and syntactic similarities, cardinality and alternativeness constraints, as well as data-ty…