Patent ID: 8074278

Claim:
A method of protecting a safety instrumented system, the method comprising: receiving a communication including an instruction to unlock the safety instrumented system, wherein the safety instrumented system is in a locked state, wherein the instruction to unlock the safety instrumented system causes the safety instrumented system to operate in a state in which the safety instrumented system is receptive to a software download; receiving the software download including updated parameters for the safety instrumented system, wherein the software download is intended for delivery and installation on the safety instrumented system; retrieving a signature from a data store configured to store a plurality of signatures, each of which is representative of a respective legitimate communication that is to be prevented from reaching the safety instrumented system; comparing the instruction and the software download to the signature; determining if the signature at least substantially matches the instruction and the software download; preventing the instruction from reaching the safety instrumented system when it is determined that the signature at least substantially matches the instruction; preventing the software download from being applied to the safety instrumented system while the safety instrumented system is in the locked state; and allowing the software download to reach the safety instrumented system when it is determined that the signature does not at least substantially match the software download or the instruction.