7 research outputs found
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
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
Fully Simulatable Quantum-Secure Coin-Flipping and Applications
We propose a coin-flip protocol which yields a string of strong, random coins
and is fully simulatable against poly-sized quantum adversaries on both sides.
It can be implemented with quantum-computational security without any set-up
assumptions, since our construction only assumes mixed commitment schemes which
we show how to construct in the given setting. We then show that the
interactive generation of random coins at the beginning or during outer
protocols allows for quantum-secure realizations of classical schemes, again
without any set-up assumptions. As example applications we discuss quantum
zero-knowledge proofs of knowledge and quantum-secure two-party function
evaluation. Both applications assume only fully simulatable coin-flipping and
mixed commitments. Since our framework allows to construct fully simulatable
coin-flipping from mixed commitments, this in particular shows that mixed
commitments are complete for quantum-secure two-party function evaluation. This
seems to be the first completeness result for quantum-secure two-party function
evaluation from a generic assumption.Comment: 27 pages; v3: updated according to final proceedings versio
Post-quantum Zero Knowledge in Constant Rounds
We construct a constant-round zero-knowledge classical argument for NP secure
against quantum attacks. We assume the existence of Quantum Fully-Homomorphic
Encryption and other standard primitives, known based on the Learning with
Errors Assumption for quantum algorithms. As a corollary, we also obtain a
constant-round zero-knowledge quantum argument for QMA.
At the heart of our protocol is a new no-cloning non-black-box simulation
technique