Say Alice wants to transmit a 10-bit key.
For the BB84 protocol, if we assume that Alice and Bob use the same basis to encode and decode 6 qubits (and different ones for the other 4), then what would be the maximum and minimum bits they might agree on?
Would the minimum number be 6 because they use the same basis 6 times and the maximum be 10? (in case Bob measures the same value even when using a different basis)
Also, since they disagree on the basis 4 times, are there $2^4$ possible runs of this protocol possible?
Extension: How would one go about doing the above analysis for B92?