On defining and achieving cryptographic security in a multiparty network

Ran Canetti

Meiran Galis, Tomislav Unkašević, Zoran Banjac +1 more

Introduction/purpose: The problem of efficient distribution of cryptographic keys in communication systems has existed since its first days and is especially emphasized by the emergence of mass communication systems. Defining and implementing efficient protocols for symmetric cryptographic keys establishment in such circumstances is of great importance in raising information security in cyberspace. Methods: Using the methods of Information Theory and Secure Multiparty Computation, protocols for direct establishment of cryptographic keys between communication parties have been defined. Results: The paper defines two new approaches to the problem of establishing cryptographic keys. The novelty in the protocol defined in the security model based on information theory is based on the source of common randomness, which in this case is the EEG signal of each subject participating in the communication system. Experimental results show that the amount of information leaking to the attacker is close to zero. A novelty in the second case, which provides security with keys at the level of computer security by applying Secure Multiparty Computation, is in the new application field, namely generation and distribution of symmetric cryptographic keys. It is characteristic of both approaches that within the framework of formal theories, it is possible to draw conclusions about their security characteristics in a formal way. Conclusions: The paper describes two new approaches for establishing cryptographic keys in symmetric cryptographic systems with experimental results. The significance of the proposed solutions lies in the fact that they enable the establishment of secure communication between communication parties from end to end, avoiding the influence of a trusted third party. In that way, the achieved communication level security significantly increases in relation to classical cryptographic systems.

Shouhuai Xu, Gendu Zhang, Hong Zhu

Elette Boyle, Abhishek Jain, Manoj Prabhakaran +1 more

In this work, we initiate the study of bottleneck complexity as a new communication efficiency measure for secure multiparty computation (MPC). Roughly, the bottleneck complexity of an MPC protocol is defined as the maximum communication complexity required by any party within the protocol execution. We observe that even without security, bottleneck communication complexity is an interesting measure of communication complexity for (distributed) functions and propose it as a fundamental area to explore. While achieving O(n) bottleneck complexity (where n is the number of parties) is straightforward, we show that: (1) achieving sublinear bottleneck complexity is not always possible, even when no security is required. (2) On the other hand, several useful classes of functions do have o(n) bottleneck complexity, when no security is required. Our main positive result is a compiler that transforms any (possibly insecure) efficient protocol with fixed communication-pattern for computing any functionality into a secure MPC protocol while preserving the bottleneck complexity of the underlying protocol (up to security parameter overhead). Given our compiler, an efficient protocol for any function f with sublinear bottleneck complexity can be transformed into an MPC protocol for f with the same bottleneck complexity. Along the way, we build cryptographic primitives - incremental fully-homomorphic encryption, succinct non-interactive arguments of knowledge with ID-based simulation-extractability property and verifiable protocol execution - that may be of independent interest.

Vaya

Donald Beaver

We introduce a new paradigm for the efficient de- sign of protocols for secure joint computation requiring minimal interaction.Instead of relying on trusted and specialized devices, unproven cryptographic assumptions, or highly interactive multiparty computations, we propose a commoditybased model in which servers provide security resources to clients but are not involved in the clients' computations themselves.Unlike oracles, which typically provide comput ational resources such as the resnlts of infeasible computations, these servers assist clients in establishing shared resources for secure computations such as oblivious transfer and circuit evaluation, broadcast and multiparty computations.Unlike protocols for secure multiparty computation, the servers themselves are "non-interactive," having no knowledge whatsoever of each other, and providing security resources in a single message.This approach to secure interactive computing obviates the need for unproven cryptographic assumptions, special hardware (such as oblivious transfer channels), completely-connected networks, or global knowledge and synchronization.It gracefully accommodates expansion without introducing bottlenecks (even polynomial) at larger scales.We give explicit constructions supporting oblivious transfer and network multicast.