The physics of no-bit-commitment : Generalized quantum non-locality versus oblivious transfer

TL;DR

This paper explores the relationship between generalized non-local correlations and quantum cryptographic tasks, revealing that stronger-than-quantum correlations do not enable bit-commitment due to their temporal ordering constraints.

Contribution

It clarifies the distinction between non-local correlations and oblivious transfer, explaining why stronger correlations do not break quantum cryptographic limitations.

Findings

Non-local correlations stronger than quantum mechanics do not enable bit-commitment.

Time-ordering of inputs and outputs prevents bit-commitment even with stronger correlations.

The paradox between non-locality and cryptographic security is resolved by analyzing temporal constraints.

Abstract

We show here that the recent work of Wolf and Wullschleger (quant-ph/0502030) on oblivious transfer apparently opens the possibility that non-local correlations which are stronger than those in quantum mechanics could be used for bit-commitment. This is surprising, because it is the very existence of non-local correlations which in quantum mechanics prevents bit-commitment. We resolve this apparent paradox by stressing the difference between non-local correlations and oblivious transfer, based on the time-ordering of their inputs and outputs, which prevents bit-commitment.