Relativistic quantum protocols: Bit commitment and coin tossing

New relativistic quantum protocols realizing the bit commitment and coin to ssing schemes are proposed. The protocols are based on the idea that spatia lly extended nonstationary orthogonal quantum states inaccessible for measu rement cannot be unambiguously distinguished. As the states are transmitted from the region controlled by one party to the region accessible for measu rement by the other party, the states become reliably distinguishable when accessed as a whole. Essential points of the protocol are both the quantum character of states and the existence of an ultimate signal propagation spe ed dictated by special relativity. (C) 2001 MAIK "Nauka/Interperiodica".