Alice and Bob
From the remaining formula_34 bits where both Alice and Bob measured in the same basis, Alice randomly chooses formula_35 bits and discloses her choices over the public channel. Both Alice and Bob announce these bits publicly and run a check to see whether more than a certain number of them agree. If this check passes, Alice and Bob proceed to use information reconciliation and privacy amplification techniques to create some number of shared secret keys. Otherwise, they cancel and start over.