System und Verfahren für die Bandbreitenreduzierung von Zeitsteuerkanälen in einem digitalen Datenverarbeitungssystem

摘要

A digital computer system for processing at least one process, said process generating operational requests for enabling selected operations. The computer system comprises a timer portion for generating two series of unpredictable timing indications. An operational processor portion is responsive to the timing indications from said timer and the operational requests for initiating operations enabled by the operational requests in response to one of the series of timing indications. The operational processor communicates with the processes regarding operations enabled with respective operational requests in response to the second series of timing indications. Since the timings of the operations by the operational processor are distinct from the timings of the communications between the operational processor and the process, the process is unable to determine timing information from the operations performed by the operational processor in response to the operational requests, thereby ensuring that the process will be unable to use the timings of the operations by the operational processor to determine timing intervals. In another aspect, the digital computer system includes a system timing generator for generating a system timing value that provides timing informatiion. The system timing generator updates the system timing value at unpredictable intervals, but so that the system timing value provides timing information that is accurate as of the time of update. When the process requests the system timing value, the system timing generator supplies only a selected high-order portion of the system timing value, also ensuring that the process only has imprecise timing information. Since the process has access to only an imprecise system timing value, and since it is unable to use external operations, by the operational processor, for timing information, the bandwidth of any covert timing channels is reduced accordingly.