A logic circuit for generation of data signatures and/or encryption of data packets to be transferred from an industrial controller snoops data as it is written to an output buffer within the industrial controller. The logic circuit generates a secure signature and/or coordinates encryption of the data packet being transferred between the shared memory location and the output buffer. If encryption of the data is required, an encryption module may both encrypt the data and generate a secure signature. If encryption is not required, the logic circuit generates the secure signature. In either case, the logic circuit controls ownership of the memory address in which the secure signature is to be written to coordinate with the MAC transferring the secure signature to the output buffer, providing a uniform interface between the SPP module and the MAC.