775 research outputs found
Emergent Behavior in Cybersecurity
We argue that emergent behavior is inherent to cybersecurity.Comment: 2 pages, HotSoS'2014 (2014 Symposium and Bootcamp on the Science of
Security
Universally composable zero-knowledge protocol using trusted platform modules
Cryptographic protocols that are established as secure in the Universally Composable (UC) model of security provide strong security assurances even when run in complex environments. Unfortunately, in order to achieve such strong security properties, UC protocols are often impractical, and most non-trivial two-party protocols cannot be secure in the UC model without some sort of external capability (or "setup assumption") being introduced. Recent work by Hofheinz et al provided an important breakthrough in designing realistic universally composable two party protocols, in which they use trusted, tamper proof hardware as a special type of helping functionality which they call a catalyst. Hofheinz et al. use government issued signature cards as a catalyst to design universally composable protocols for zero-knowledge proofs and commitments, but did not give a complete security proof for either protocol.
In this thesis, we consider another form of security hardware, Trusted Platform Modules (TPMs), which are more widespread than signature cards and are currently shipped as a part of almost every business laptop or desktop. Trusted Module Platforms are tamper evident devices which support cryptographic functionalities including digital signatures, but have a different key management model from signature cards. In this thesis we consider TPMs as catalysts and describe a universally composable zero knowledge protocol using Trusted Platform Modules. We also present a complete security proof for both the Hofheinz's universally composable zero knowledge protocol from signature cards and our universally composable zero knowledge protocol using TPMs as a catalyst
Universally Composable Quantum Multi-Party Computation
The Universal Composability model (UC) by Canetti (FOCS 2001) allows for
secure composition of arbitrary protocols. We present a quantum version of the
UC model which enjoys the same compositionality guarantees. We prove that in
this model statistically secure oblivious transfer protocols can be constructed
from commitments. Furthermore, we show that every statistically classically UC
secure protocol is also statistically quantum UC secure. Such implications are
not known for other quantum security definitions. As a corollary, we get that
quantum UC secure protocols for general multi-party computation can be
constructed from commitments
Improved Black-Box Constructions of Composable Secure Computation
We close the gap between black-box and non-black-box constructions of secure multiparty computation in the plain model under the assumption of semi-honest oblivious transfer. The notion of protocol composition we target is security, or more precisely, security with super-polynomial helpers. In this notion, both the simulator and the adversary are given access to an oracle called an that can perform some predefined super-polynomial time task. Angel-based security maintains the attractive properties of the universal composition framework while providing meaningful security guarantees in complex environments without having to trust anyone.
Angel-based security can be achieved using non-black-box constructions in rounds where is the round-complexity of the semi-honest oblivious transfer. However, currently, the best known constructions under the same assumption require rounds. If is a constant, the gap between non-black-box and black-box constructions can be a multiplicative factor . We close this gap by presenting a -round black-box construction. We achieve this result by constructing constant-round 1-1 CCA-secure commitments assuming only black-box access to one-way functions
New Notions of Security: Achieving Universal Composability without Trusted Setup
We propose a modification to the framework of Universally Composable (UC) security [3]. Our new notion, involves comparing the protocol executions with an ideal execution involving ideal functionalities (just as in UC-security), but allowing the environment and adversary access to some super-polynomial computational power. We argue the meaningfulness of the new notion, which in particular subsumes many of the traditional notions of security. We generalize the Universal Composition theorem of [3] to the new setting. Then under new computational assumptions, we realize secure multi-party computation (for static adversaries) without a common reference string or any other set-up assumptions, in the new framework. This is known to be impossible under the UC framework.
Quantum Cryptography Beyond Quantum Key Distribution
Quantum cryptography is the art and science of exploiting quantum mechanical
effects in order to perform cryptographic tasks. While the most well-known
example of this discipline is quantum key distribution (QKD), there exist many
other applications such as quantum money, randomness generation, secure two-
and multi-party computation and delegated quantum computation. Quantum
cryptography also studies the limitations and challenges resulting from quantum
adversaries---including the impossibility of quantum bit commitment, the
difficulty of quantum rewinding and the definition of quantum security models
for classical primitives. In this review article, aimed primarily at
cryptographers unfamiliar with the quantum world, we survey the area of
theoretical quantum cryptography, with an emphasis on the constructions and
limitations beyond the realm of QKD.Comment: 45 pages, over 245 reference
Generation and Distribution of Quantum Oblivious Keys for Secure Multiparty Computation
The oblivious transfer primitive is sufficient to implement secure multiparty
computation. However, secure multiparty computation based only on classical
cryptography is severely limited by the security and efficiency of the
oblivious transfer implementation. We present a method to efficiently and
securely generate and distribute oblivious keys by exchanging qubits and by
performing commitments using classical hash functions. With the presented
hybrid approach, quantum and classical, we obtain a practical and high-speed
oblivious transfer protocol, secure even against quantum computer attacks. The
oblivious distributed keys allow implementing a fast and secure oblivious
transfer protocol, which can pave the way for the widespread of applications
based on secure multiparty computation.Comment: 11 pages, 5 figure
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