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In this work, we study position-based cryptography in the quantum setting. The aim is to use the geographical position of a party as its only credential. On the negative side, we show that if adversaries are allowed to share an arbitrarily large entangled quantum state, no secure position-verification is possible at all. That is, we show a generic attack(More)
The nonlocal behavior of quantum mechanics can be used to generate guaranteed fresh randomness from an untrusted device that consists of two nonsignalling components; since the generation process requires some initial fresh randomness to act as a catalyst, one also speaks of randomness expansion. R. Colbeck and A. Kent [J. Phys. A 44, 095305 (2011)](More)
—We revisit the problem of reliable interactive communication over a noisy channel, and obtain the first fully explicit (randomized) efficient constant-rate emulation procedure for reliable interactive communication. Our protocol works for any discrete memoryless noisy channel with constant capacity, and fails with exponentially small probability in the(More)
Error correction and message authentication are well studied in the literature, and various efficient solutions have been suggested and analyzed. This is however not the case for data streams in which the message is very long, possibly infinite, and not known in advance to the sender. Trivial solutions for error-correcting and authenticating data streams(More)
— We revisit the problem of reliable interactive communication over a noisy channel and obtain the first fully (randomized) efficient constant-rate emulation procedure for reliable interactive communication. Our protocol works for any discrete memoryless noisy channel with constant capacity and fails with exponentially small probability in the total length(More)
We provide tight upper and lower bounds on the noise resilience of interactive communication over noisy channels with <i>feedback</i>. In this setting, we show that the maximal fraction of noise that any robust protocol can resist is 1/3. Additionally, we provide a simple and efficient robust protocol that succeeds as long as the fraction of noise is at(More)
Consider two parties Alice and Bob, who hold private inputs <i>x</i> and <i>y</i>, and wish to compute a function <i>f(x, y)</i> <i>privately</i> in the information theoretic sense; that is, each party should learn nothing beyond <i>f(x, y)</i>. However, the communication channel available to them is <i>noisy</i>. This means that the channel can introduce(More)
In this work, we study the fundamental problem of reliable interactive communication over a noisy channel. In a breakthrough sequence of papers published in 1992 and 1993 [Sch92, Sch93], Schulman gave non-constructive proofs of the existence of general methods to emulate any two-party interactive protocol such that: (1) the emulation protocol only takes a(More)
Theoretical quantum key distribution (QKD) protocols commonly rely on the use of qubits (quantum bits). In reality, however, due to practical limitations, the legitimate users are forced to employ a larger quantum (Hilbert) space, say a quhexit (quantum six-dimensional) space, or even a much larger quantum Hilbert space. Various specific attacks exploit of(More)