Spacetime-constrained oblivious transfer
Damián Pitalúa-García · Physical Review A · 2016
In 1-out-of-2 oblivious transfer (OT), Alice inputs numbers ${x}_{0},{x}_{1}$, Bob inputs a bit $b$ and outputs ${x}_{b}$. Secure OT requires that Alice and Bob learn nothing about $b$ and ${x}_{\overline{b}}$, respectively. We define spacetime-constrained oblivious transfer (SCOT) as OT in Minkowski spacetime in which Bob must output ${x}_{b}$ within ${R}_{b}$, where ${R}_{0}$ and ${R}_{1}$ are fixed spacelike separated spacetime regions. We show that unconditionally secure SCOT is impossible with classical protocols in Minkowski (or Galilean) spacetime, or with quantum protocols in Galilean spacetime. We describe a quantum SCOT protocol in Minkowski spacetime, and we show it unconditionally secure.