  Given a communication system using quantum key distribution, the receiver can
be seen as one who tries to guess the sender's information just as potential
eavesdroppers do. The receiver-eavesdropper similarity thus implies a simple
relation in terms of guessing probability and correctness of sifted keys,
related with the distance-based, information-theoretic security. The tolerable
regions of error rates determined by such a guessing-probability-based relation
are shown to be close to those determined by security criteria. Thus, an
alternative perspective on applying guessing probability in analyzing quantum
key distribution issues is here provided. Examples of two specific protocols
are illustrated. Our results contribute to evaluating an important element in
communication study, and may provide useful reference for the security analysis
of quantum key distribution protocols.
