Security of differential phase shift quantum key distribution against individual attacks

Edo Waks, Hiroki Takesue, Yoshihisa Yamamoto

Published 2005-08-15, updated 2005-08-16Version 2

We derive a proof of security for the Differential Phase Shift Quantum Key Distribution (DPSQKD) protocol under the assumption that Eve is restricted to individual attacks. The security proof is derived by bounding the average collision probability, which leads directly to a bound on Eve's mutual information on the final key. The security proof applies to realistic sources based on pulsed coherent light. We then compare individual attacks to sequential attacks and show that individual attacks are more powerful.