Presented is a method for determining the maximum number of key selection vectors (KSVs) supported by an HDCP source. The method includes providing a number of KSVs to the HDCP source, determining whether the HDCP source has entered a failure mode in response to the provided number of KSVs, increasing or decreasing the number of KSVs in response to the HDCP source not entering or entering the failure mode, providing the increased or decreased number of KSVs to the HDCP source, determining whether the HDCP source has entered the failure mode in response to the provided increased or decreased number of KSVs, and repeating the increasing, decreasing, and determining steps until the difference between a lowest number of provided KSVs resulting in the HDCP source entering the failure mode and a highest number of provided KSVs resulting in the HDCP source not entering the failure mode is one.