1. A microprocessor comprising: a multistage instruction processing pipeline, comprising at least one of branch prediction logic elements and speculative execution logic elements, and having a minimum pipeline latency between receipt of a first instruction of a sequence of instructions and readiness for commitment of execution of the first instruction, configured to: receive a sequence of instructions for processing, concurrently decode the received instructions during the pipeline latency, dispatch the instructions, advance respective instructions of the sequence of instructions to a stage prior to commitment of instruction execution, commit execution of the sequence of instructions to produce at least one execution result comprising alteration of at least one register of the microprocessor external to the instruction processing pipeline in response to execution of at least one instruction and an availability of a verification signal, and respond to at least one of a misprediction signal and failure of availability of the verification signal, to cause a rollback of the instruction processing pipeline to a state prior to an error which caused the at least one of the misprediction signal and the failure of availability of the verification signal; a memory configured to store at least a predetermined encrypted reference digital signature; decryption logic elements configured to decrypt the encrypted reference digital signature in dependence on a decryption key securely stored in, and received from a secure hardware environment to produce a reference digital signature corresponding to an expected digital signature of an authentic sequence of instructions; verification logic elements configured to match the reference digital signature with a digital signature of the received sequence of instructions; and authorization logic elements configured, within a first mode of operation, to generate the verification signal within the minimum pipeline latency, contingent upon verifying that the reference digital signature matches the digital signature.