636 research outputs found
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
Oblivious Transfer is in MiniQCrypt
MiniQCrypt is a world where quantum-secure one-way functions exist, and quantum communication is possible. We construct an oblivious transfer (OT) protocol in MiniQCrypt that achieves simulation-security in the plain model against malicious quantum polynomial-time adversaries, building on the foundational work of Bennett, Brassard, Crépeau and Skubiszewska (CRYPTO 1991). Combining the OT protocol with prior works, we obtain secure two-party and multi-party computation protocols also in MiniQCrypt. This is in contrast to the classical world, where it is widely believed that one-way functions alone do not give us OT.
In the common random string model, we achieve a constant-round universally composable (UC) OT protocol
A Framework for Efficient Adaptively Secure Composable Oblivious Transfer in the ROM
Oblivious Transfer (OT) is a fundamental cryptographic protocol that finds a
number of applications, in particular, as an essential building block for
two-party and multi-party computation. We construct a round-optimal (2 rounds)
universally composable (UC) protocol for oblivious transfer secure against
active adaptive adversaries from any OW-CPA secure public-key encryption scheme
with certain properties in the random oracle model (ROM). In terms of
computation, our protocol only requires the generation of a public/secret-key
pair, two encryption operations and one decryption operation, apart from a few
calls to the random oracle. In~terms of communication, our protocol only
requires the transfer of one public-key, two ciphertexts, and three binary
strings of roughly the same size as the message. Next, we show how to
instantiate our construction under the low noise LPN, McEliece, QC-MDPC, LWE,
and CDH assumptions. Our instantiations based on the low noise LPN, McEliece,
and QC-MDPC assumptions are the first UC-secure OT protocols based on coding
assumptions to achieve: 1) adaptive security, 2) optimal round complexity, 3)
low communication and computational complexities. Previous results in this
setting only achieved static security and used costly cut-and-choose
techniques.Our instantiation based on CDH achieves adaptive security at the
small cost of communicating only two more group elements as compared to the
gap-DH based Simplest OT protocol of Chou and Orlandi (Latincrypt 15), which
only achieves static security in the ROM
Composable Security in the Bounded-Quantum-Storage Model
We present a simplified framework for proving sequential composability in the
quantum setting. In particular, we give a new, simulation-based, definition for
security in the bounded-quantum-storage model, and show that this definition
allows for sequential composition of protocols. Damgard et al. (FOCS '05,
CRYPTO '07) showed how to securely implement bit commitment and oblivious
transfer in the bounded-quantum-storage model, where the adversary is only
allowed to store a limited number of qubits. However, their security
definitions did only apply to the standalone setting, and it was not clear if
their protocols could be composed. Indeed, we first give a simple attack that
shows that these protocols are not composable without a small refinement of the
model. Finally, we prove the security of their randomized oblivious transfer
protocol in our refined model. Secure implementations of oblivious transfer and
bit commitment then follow easily by a (classical) reduction to randomized
oblivious transfer.Comment: 21 page
Classical Cryptographic Protocols in a Quantum World
Cryptographic protocols, such as protocols for secure function evaluation
(SFE), have played a crucial role in the development of modern cryptography.
The extensive theory of these protocols, however, deals almost exclusively with
classical attackers. If we accept that quantum information processing is the
most realistic model of physically feasible computation, then we must ask: what
classical protocols remain secure against quantum attackers?
Our main contribution is showing the existence of classical two-party
protocols for the secure evaluation of any polynomial-time function under
reasonable computational assumptions (for example, it suffices that the
learning with errors problem be hard for quantum polynomial time). Our result
shows that the basic two-party feasibility picture from classical cryptography
remains unchanged in a quantum world.Comment: Full version of an old paper in Crypto'11. Invited to IJQI. This is
authors' copy with different formattin
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
Composable security of delegated quantum computation
Delegating difficult computations to remote large computation facilities,
with appropriate security guarantees, is a possible solution for the
ever-growing needs of personal computing power. For delegated computation
protocols to be usable in a larger context---or simply to securely run two
protocols in parallel---the security definitions need to be composable. Here,
we define composable security for delegated quantum computation. We distinguish
between protocols which provide only blindness---the computation is hidden from
the server---and those that are also verifiable---the client can check that it
has received the correct result. We show that the composable security
definition capturing both these notions can be reduced to a combination of
several distinct "trace-distance-type" criteria---which are, individually,
non-composable security definitions.
Additionally, we study the security of some known delegated quantum
computation protocols, including Broadbent, Fitzsimons and Kashefi's Universal
Blind Quantum Computation protocol. Even though these protocols were originally
proposed with insufficient security criteria, they turn out to still be secure
given the stronger composable definitions.Comment: 37+9 pages, 13 figures. v3: minor changes, new references. v2:
extended the reduction between composable and local security to include
entangled inputs, substantially rewritten the introduction to the Abstract
Cryptography (AC) framewor
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