Unconditionally secure relativistic multi-party biased coin flipping and die rolling

Abstract

We introduce relativistic multi-party biased die-rolling protocols, generalizing coin flipping to M ≥ 2 parties and to N ≥ 2 outcomes for any chosen outcome biases and show them unconditionally secure. Our results prove that the most general random secure multi-party computation, where all parties receive the output and there is no secret input by any party, can be implemented with unconditional security. Our protocols extend Kent’s (Kent A. 1999 Phys. Rev. Lett. 83 , 5382) two-party unbiased coin-flipping protocol, do not require any quantum communication, are practical to implement with current technology and to our knowledge are the first multi-party relativistic cryptographic protocols.