Unconditional security at a low cost

In this talk, I will discuss several post-processing schemes for quantum key distribution (QKD). I will compare QKD with and without decoy states. By simulating four QKD experiments and analyzing one decoy-state QKD experiment, we compare two data postprocessing schemes based on security against individual attacks by L\"{u}tkenhaus, and unconditional security analysis by Gottesman-Lo-L\"{u}tkenhaus-Preskill. Our results show that these two schemes yield close performances. In QKD, since unconditional security is highly sought after, we conclude that one is better off considering unconditional security, rather than restricting to individual attacks. This work is appeared in Ref.~[X. Ma, Phys.~Rev.~A \emph{74}, 052325, (2006)].