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- Harry Buhrman, Nishanth Chandran, +4 authors Christian Schaffner
- SIAM J. Comput.
- 2010

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)

- Serge Fehr, Ran Gelles, Christian Schaffner
- ArXiv
- 2011

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)

- Ran Gelles, Ankur Moitra, Amit Sahai
- 2011 IEEE 52nd Annual Symposium on Foundations of…
- 2011

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 memory less noisy channel with constant capacity, and fails with exponentially small probability in the… (More)

- Matthew K. Franklin, Ran Gelles, Rafail Ostrovsky, Leonard J. Schulman
- IEEE Transactions on Information Theory
- 2012

We consider the task of communicating a data stream-a long, possibly infinite message not known in advance to the sender-over a channel with adversarial noise. For any given noise rate c <; 1, we show an efficient, constant-rate scheme that correctly decodes a (1 - c) fraction of the stream sent so far with high probability, or aborts if the noise rate… (More)

- Ran Gelles, Ankur Moitra, Amit Sahai
- IEEE Transactions on Information Theory
- 2011

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 of… (More)

- Shweta Agrawal, Ran Gelles, Amit Sahai
- 2016 IEEE International Symposium on Information…
- 2016

How much adversarial noise can protocols for interactive communication tolerate? This question was examined by Braverman and Rao (IEEE Trans. Inf. Theory, 2014) for the case of “robust” protocols, where each party sends messages only in fixed and predetermined rounds. We consider a new class of protocols for interactive communication, which we… (More)

- Klim Efremenko, Ran Gelles, Bernhard Haeupler
- IEEE Transactions on Information Theory
- 2015

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)

- Ran Gelles, Amit Sahai
- ArXiv
- 2011

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)

- Ran Gelles, Tal Mor
- 2008

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)

- Ran Gelles, Amit Sahai, Akshay Wadia
- IEEE Transactions on Information Theory
- 2013

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)