256 research outputs found
The Impossibility Of Secure Two-Party Classical Computation
We present attacks that show that unconditionally secure two-party classical
computation is impossible for many classes of function. Our analysis applies to
both quantum and relativistic protocols. We illustrate our results by showing
the impossibility of oblivious transfer.Comment: 10 page
Flexible and Robust Privacy-Preserving Implicit Authentication
Implicit authentication consists of a server authenticating a user based on
the user's usage profile, instead of/in addition to relying on something the
user explicitly knows (passwords, private keys, etc.). While implicit
authentication makes identity theft by third parties more difficult, it
requires the server to learn and store the user's usage profile. Recently, the
first privacy-preserving implicit authentication system was presented, in which
the server does not learn the user's profile. It uses an ad hoc two-party
computation protocol to compare the user's fresh sampled features against an
encrypted stored user's profile. The protocol requires storing the usage
profile and comparing against it using two different cryptosystems, one of them
order-preserving; furthermore, features must be numerical. We present here a
simpler protocol based on set intersection that has the advantages of: i)
requiring only one cryptosystem; ii) not leaking the relative order of fresh
feature samples; iii) being able to deal with any type of features (numerical
or non-numerical).
Keywords: Privacy-preserving implicit authentication, privacy-preserving set
intersection, implicit authentication, active authentication, transparent
authentication, risk mitigation, data brokers.Comment: IFIP SEC 2015-Intl. Information Security and Privacy Conference, May
26-28, 2015, IFIP AICT, Springer, to appea
Information-Theoretic Broadcast with Dishonest Majority for Long Messages
Byzantine broadcast is a fundamental primitive for secure computation. In a setting with parties in the presence of an adversary controlling at most parties,
while a lot of progress in optimizing communication complexity has been made for , little progress has been made for the general case , especially for information-theoretic security. In particular, all information-theoretic secure broadcast protocols for -bit messages and and optimal round complexity have, so far, required a communication complexity of . A broadcast extension protocol allows a long message to be broadcast more efficiently using a small number of single-bit broadcasts. Through broadcast extension, so far, the best achievable round complexity for setting with the optimal communication complexity
of is rounds.
In this work, we construct a new broadcast extension protocol for with information-theoretic security. Our protocol improves the round complexity to while maintaining the optimal communication complexity for long messages. Our result shortens the gap between the information-theoretic setting and the computational setting, and between the optimal communication protocol and the optimal round protocol in the information-theoretic setting for
A taxonomy of single sign-on systems
Abstract. At present, network users have to manage one set of authentication credentials (usually a username/password pair) for every service with which they are registered. Single Sign-On (SSO) has been proposed as a solution to the usability, security and management implications of this situation. Under SSO, users authenticate themselves only once and are logged into the services they subsequently use without further manual interaction. Several architectures for SSO have been developed, each with different properties and underlying infrastructures. This paper presents a taxonomy of these approaches and puts some of the SSO schemes, services and products into that context. This enables decisions about the design and selection of future approaches to SSO to be made within a more structured context; it also reveals some important differences in the security properties that can be provided by various approaches.
Secure Mobile Support of Independent Sales Agencies
Sales agents depend on mobile support systems for their daily work. Independent sales agencies, however, are not able to facilitate this kind of mobile support on their own due to their small size and lack of the necessary funds. Since their processes correlate with confidential information and include the initiation and alteration of legally binding transactions they have a high need for security. In this contribution we first propose an IT-artifact consisting of a service platform that supports multi-vendor sales processes based on previous work. We then analyze use cases of sales representatives of independent sales agencies using this system and derive their security requirements. We then propose a security extension to the IT-artifact and evaluate this extension by comparing it to existing solutions. Our results show that the proposed artifact extension provides a more convenient and secure solution than already existing approaches
Composability in quantum cryptography
In this article, we review several aspects of composability in the context of
quantum cryptography. The first part is devoted to key distribution. We discuss
the security criteria that a quantum key distribution protocol must fulfill to
allow its safe use within a larger security application (e.g., for secure
message transmission). To illustrate the practical use of composability, we
show how to generate a continuous key stream by sequentially composing rounds
of a quantum key distribution protocol. In a second part, we take a more
general point of view, which is necessary for the study of cryptographic
situations involving, for example, mutually distrustful parties. We explain the
universal composability framework and state the composition theorem which
guarantees that secure protocols can securely be composed to larger
applicationsComment: 18 pages, 2 figure
Service and Protocol Architecture for the MAFTIA Middleware
This document describes the specification of the MAFTIA middleware architecture. This specification focusses on the models, building blocks and services. It describes the tradeoffs made in terms of models, the choices of building blocks and their topology, and the portfolio of services to be offered by the MAFTIA middleware to applications and high-level services. In particular, regarding the system model, it presents a detailed discussion on the fault, synchrony, topological, and group models, which were used to guide the overall architecture. The architecture was divided into two main levels, the site part which connects to the network and handles all inter-host operations, and a participant part which takes care of all distributed activities and relies on the services provided by the site-part component
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