A processing system (60) includes an input interface (62), a first processor (64), a second processor (66), and an output interface (68) arranged in a serial configuration. Each of the input interface (62), first processor (64), second processor (66), and output interface (68) computes a digest (92, 100, 110, and 114) using information, e.g., a unique parameter (94, 102, 112, 118), known only by that element (62, 64, 66, 68) and using information generated by that element (62, 64, 66, 68). The digests (92, 100, 110, and 114) are used to validate the integrity of payload data (86) processed by the system (60) to form processed data (104) and the system (60) only outputs the processed data (104) upon validation of data integrity. The serial configuration of system (60) may be implemented to provide high bit rate, redundant cryptographic services.