  It has been shown that in the asymptotic case of infinite-key length the
2-decoy state QKD protocol outperforms the 1-decoy state protocol. Here, we
present a finite-key analysis of the 1-decoy method. Interestingly, we find
that for practical block sizes of up to $10^8$ bits, the 1-decoy protocol
achieves for almost all experimental settings higher secret key rates than the
2-decoy protocol. Since using only one decoy is also easier to implement, we
conclude that it is the best choice for practical QKD.
