1. A method of processing payload data in a serial arrangement of processors, said serial arrangement of processors including at least a first processor and a final processor, said method comprising: at an input interface, computing a first digest using said payload data and a parameter unique to said input interface and generating a first message that includes said payload data and said first digest; at each of said processors: a) receiving an incoming message; b) processing data contained in said incoming message to produce processed data; c) computing an output digest using an input digest contained in said incoming message, said processed data, and a parameter unique to said processor; and d) generating an outgoing message that includes said output digest and one of said payload data and said processed data, wherein said incoming message received by said first processor comprises said first message such that said input digest for said first processor is said first digest, said incoming message received by each processor following said first processor is said outgoing message generated by an immediately preceding processor such that said input digest is said output digest computed by said immediately preceding processor, and said outgoing message generated by said final processor includes said processed data; and at an output interface, receiving said outgoing message from said final processor, computing a validation digest using said output digest contained in said outgoing message, said processed data, and a parameter unique to said output interface, and outputting said processed data when said validation digest matches a predetermined value.