  This paper reports a variant of the three-stage quantum cryptography protocol
which can be used in low intensity laser output regimes. The variant, which
tracks the intensity of the laser beam at the intermediate stages, makes the
task of the eavesdropper harder than the standard K06 protocol. The constraints
on the iAQC protocol are much less than those on BB84 and in principle it can
not only be used for key distribution but also for direct bitwise encryption of
data. The iAQC protocol is an improvement on the K06 protocol in that it makes
it harder for the eavesdropper to monitor the channel.
