Secure quantum signatures using insecure quantum channels

Digital signatures are widely used in modern communication to guarantee authenticity and transferability of messages. The security of currently used classical schemes relies on computational assumptions. We present a quantum signature scheme that does not require trusted quantum channels. We prove that it is unconditionally secure against the most general coherent attacks, and show that it requires the transmission of significantly fewer quantum states than previous schemes. We also show that the quantum channel noise threshold for our scheme is less strict than for distilling a secure key using quantum key distribution. This shows that “direct” quantum signature schemes can be preferable to signature schemes relying on secret shared keys generated using quantum key distribution.This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) under EP/G009821/1 and EP/K022717/1. P.W. gratefully acknowledges support from the COST Action MP1006. A.K. was partially supported by a grant from FQXi and by Perimeter Institute for Theoretical Physics. Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Research and Innovation.This is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevA.93.03232