20 research outputs found
Unconditionally Secure Bit Commitment by Transmitting Measurement Outcomes
We propose a new unconditionally secure bit commitment scheme based on
Minkowski causality and the properties of quantum information. The receiving
party sends a number of randomly chosen BB84 qubits to the committer at a given
point in space-time. The committer carries out measurements in one of the two
BB84 bases, depending on the committed bit value, and transmits the outcomes
securely at light speed in opposite directions to remote agents. These agents
unveil the bit by returning the outcomes to adjacent agents of the receiver.
The security proofs rely only on simple properties of quantum information and
the impossibility of superluminal signalling.Comment: Discussion expanded pedagogically in response to referee comment
Device-Independent Relativistic Quantum Bit Commitment
We examine the possibility of device-independent relativistic quantum bit
commitment. We note the potential threat of {\it location attacks}, in which
the behaviour of untrusted devices used in relativistic quantum cryptography
depends on their space-time location. We describe relativistic quantum bit
commitment schemes that are immune to these attacks, and show that these
schemes offer device-independent security against hypothetical post-quantum
adversaries subject only to the no-signalling principle. We compare a
relativistic classical bit commitment scheme with similar features, and note
some possible advantages of the quantum schemes
Location-Oblivious Data Transfer with Flying Entangled Qudits
We present a simple and practical quantum protocol involving two mistrustful
agencies in Minkowski space, which allows Alice to transfer data to Bob at a
spacetime location that neither can predict in advance. The location depends on
both Alice's and Bob's actions. The protocol guarantees unconditionally to
Alice that Bob learns the data at a randomly determined location; it guarantees
to Bob that Alice will not learn the transfer location even after the protocol
is complete.
The task implemented, transferring data at a space-time location that remains
hidden from the transferrer, has no precise analogue in non-relativistic
quantum cryptography. It illustrates further the scope for novel cryptographic
applications of relativistic quantum theory.Comment: References updated. Published versio