In this talk, we provide a security proof of the Bennett-Brassard 1984 (BB84) quantum key distribution protocol for arbitrary source and detector. The assumption in the security proof is that the source is characterized; that is, the proof requires no restrictions on the source and detector, and, moreover, the detector can be uncharacterized. The proof is performed by lower-bounding adversary's Renyi entropy about the key before privacy amplification.