A method for protecting the digital output signal of a security module, comprising the steps of: receiving a scrambled digital signal from a source external to said security module, recovering at least one transport scramble control flag from the scrambled digital signal, descrambling said received scrambled signal to generate a descrambled signal, monitoring the at least one transport scramble control flag, generating a scrambling key in response to said monitored at least one transport scramble control flag, and scrambling said descrambled signal using said scrambling key to generate a re-scrambled signal. The present invention also includes a conditional access system comprising a host device and a security device coupled to the host device, such that the security device includes at least one transport scramble control flag modification circuit. By monitoring the transport scramble control flag as content passes through the security module, protection of the content can be securely maintained.