US5220661A
Expired / Lapsed
US
⏱️ 0.0 years remaining
System and method for reducing timing channels in digital data processing systems
Assignee: Hewlett Packard Development Co LP
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Filing: 1992-01-14
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Granted: 1993-06-15
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Expires: 2012-01-14
Abstract
Abstract 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 information. 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 convert timing channels is reduced accordingly.
Inventors
- 👤 Wei-Ming Hu
- 👤 Clifford E. Kahn
- 👤 Paul A. Karger
- 👤 Andrew H. Mason
- 👤 Paul T. Robinson
- 👤 John C. R. Wray
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 09:52
CPC Classifications
G; G06; G06F; G06F21/00; G06F21/70; G06F21/71; G06F21/72; G06F21/725; G06F9/00; G06F9/06; G06F9/46; G06F9/54; G06F9/542
Claims Analysis
Total Claims: 44
Claim 1
Independent Claim
228 words
A digital computer system for processing a process, said system comprising a timing indication generator that generates timing indications of a first type and timing indications of a second type, the timing indications of the first type being separated from the timing indications of the second type by intervals of random duration that are unpredictable to the process, first and second service providers for providing services to said process, said process interacting with each of said service providers, means responsive to a timing indication of the first type for scheduling the occurrence of an event of a first kind relating to the interactions between said process and said first service provider, wherein said first service provider generates a first signal indicating occurrence of an event of a first kind, means responsive to said first signal and to occurrence of a timing indication of the second type for scheduling the occurrence of an event of a second kind relating to the interactions between said process and said second service provider, wherein said second service provider generates a second signal sufficient to indicate the occurrence of said event of a second kind, said second signal being unknown to said process, and means responsive to said second signal and to said timing indications of the first type for indicating to said process the occurrence of said event of a second kind.
Claim 2
Dependent Claim
228 words
A digital computer system for processing a process, said system comprising a timing indication generator that generates timing indications of a first type and timing indications of a second type, the timing indications of the first type being separated from the timing indications of the second type by intervals of random duration that are unpredictable to the process, first and second service providers for providing services to said process, said process interacting with each of said service providers, means responsive to a timing indication of the first type for scheduling the occurrence of an event of a first kind relating to the interactions between said process and said first service provider, wherein said first service provider generates a first signal indicating occurrence of an event of a first kind, means responsive to said first signal and to occurrence of a timing indication of the second type for scheduling the occurrence of an event of a second kind relating to the interactions between said process and said second service provider, wherein said second service provider generates a second signal sufficient to indicate the occurrence of said event of a second kind, said second signal being unknown to said process, and means responsive to said second signal and to said timing indications of the first type for indicating to said process the occurrence of said event of a second kind.
Claim 3
Dependent Claim
90 words
The computer system of claim 1 wherein said means responsive to a timing indication of said first type comprises a process scheduler responsive to said timing indication of said first type to schedule the initiation of processing of said process, and said means responsive to said first signal and to the occurrence of a timing indication of the second type comprises a request processor for responding to requests from said process, said request processor delaying events relating to said requests until the occurrence of timing indications of the second type.
Claim 4
Dependent Claim
21 words
The computer system of claim 2 wherein said request processor is an IO interface and said requests are for IO operations.
Claim 5
Dependent Claim
25 words
The computer system of claim 3, wherein said IO interface delays said requests for IO operations in response to timing indications of said second type.
Claim 6
Dependent Claim
33 words
The computer system of claim 4, wherein said IO interface delays requests for ones of said IO operations having observable interim progress until an occurrence of a timing indication of said second type.
Claim 7
Dependent Claim
37 words
The computer system of claim 10, wherein said IO interface further includes a request buffer for buffering said IO operation requests from said process, said request buffer being responsive to said timing indications of said second type.
Claim 8
Dependent Claim
39 words
The computer system of claim 5, wherein said IO interface delays until an occurrence of a timing indication of said second type requests for ones of said IO operations whose interim progress is observable by reqeusting further IO operations.
Claim 9
Dependent Claim
38 words
The computer system of claim 7, wherein said IO interface delays until an occurrence of a timing indication of said second type requests for ones of said IO operations that render the progress of other IO operations observable.
Claim 10
Dependent Claim
25 words
The computer system of claim 3, wherein said IO interface buffers said requests for IO operations in response to timing indications of said second type.
Claim 11
Dependent Claim
42 words
The computer system of claim 3, wherein requests for ones of said IO operations that are externally observable as occurring between two successive timing indications of said first type are delayed until an occurrence of a timing indication of said second type.
Claim 12
Dependent Claim
62 words
The computer system of claim 10, said IO interface further including a staging buffer for buffering said IO operation requests, said staging buffer being responsive to said timing indications of said first type, and a request buffer responsive to said timing indications of said second type and to said staging buffer to receive and buffer requests previously buffered in said staging buffer.
Claim 13
Dependent Claim
31 words
The computer system of claim 3, wherein events relating to ones o said IO operations whose interim progress is unobservable and that are not externally observable are allowed to proceed unbuffered.
Claim 14
Dependent Claim
29 words
The computer system of claim 3, wherein said IO interface buffers the notifications of events related to said IO operations in response to timing indications of said second type.
Claim 15
Dependent Claim
99 words
The computer system of claim 13, said IO interface further including a system completion packet queue for storing completion packets generated when said IO operations are completed, a per-process completion packet queue responsive to timing indications of said second type and to said system completion packet queue to receive said completion packets from said system completion packet queue, and an event notifier responsive to said per-process queue and to timing indications of said second type, for notifying said process of the presence of completion packets in said per-process queue in response to a timing indication of said second type.
Claim 16
Dependent Claim
27 words
The computer system of claim 3, further including ring buffers for buffering said requests for said IO operations in response to timing indications of said second type.
Claim 17
Dependent Claim
59 words
The computer system of claim 1 or 2 wherein said timing indication generator also generates a system time value, said system time value being a running indication of time that is available to said process, and further including means responsive to said timing indication generator for providing a representation of said value that is less accurate than said value.
Claim 18
Dependent Claim
25 words
The computer system of claim 16, wherein the representation of said value that is less accurate than said value is computed by truncating said value.
Claim 19
Dependent Claim
21 words
The computer system of claim 16, wherein said representation is updated only in response to timing indications of said second type.
Claim 20
Dependent Claim
16 words
The computer system of claim 1 or 2 wherein said timing indication generator comprises a timer.
Claim 21
Dependent Claim
22 words
The computer system of claim 2 wherein said timing indications of the first and second types are generated in an alternating manner.
Claim 22
Dependent Claim
21 words
The computer system of claim 2 further including a further timing indication generator for generating a further series of timing indications.
Claim 23
Dependent Claim
17 words
The computer system of claim 21 wherein said further timing indication generator is within an IO device.
Claim 24
Dependent Claim
23 words
The computer system of claim 21 further including a plurality of processors and wherein separate timing indication generators are associated with separate processors.
Claim 25
Dependent Claim
19 words
The computer system of claim 21 wherein said further timing indication generator generates timing indications of said second type.
Claim 26
Dependent Claim
53 words
The computer system of claim 1 or 2 wherein said timing indication generator includes a tick counter for counting timing signals and for generating one of said timing indications when said tick counter has counted out, and an unpredictable number store for re-loading said tick counter when said tick counter has counted out.
Claim 27
Dependent Claim
36 words
The computer system of claim 25, wherein each unpredictable number that is loaded from said unpredictable number store into said tick counter is also added to a system time value in response to said timing indications.
Claim 28
Dependent Claim
15 words
The computer of claim 25, further including a timing source for generating said timing signals.
Claim 29
Dependent Claim
72 words
The computer system of claim 2 wherein said timing indication generator includes a tick counter for counting timing signals and for generating one of said timing indications when said tick counter has counted out, an unpredictable number store for re-loading said tick counter when said tick counter has counted out, and a tick selector responsive to timing indications from said tick counter for generating said first and second types of timing indications.
Claim 30
Dependent Claim
15 words
The computer of claim 28, further including a timing source for generating said timing signals.
Claim 31
Dependent Claim
145 words
A digital computer system comprising: a timing indication generator that generates timing indications of a first type and timing indications of a second type, the timing indications of the first type being separated from the timing indications of the second type by intervals of random durations that are unpredictable to a process, and an IO interface responsive to said timing indications of said first type and to said timing indications of said second type, for processing requests for IO operations, said IO interface buffering said request for IO operations in response to said timing indications of said second type, and buffering notifications of events related to said processing of said requests for IO operations in response to (a) said timing indications of said first type, (b) said requests for IO operations, and (c) said events related to said processing of said requests for IO operations.
Claim 32
Dependent Claim
145 words
A digital computer system comprising: a timing indication generator that generates timing indications of a first type and timing indications of a second type, the timing indications of the first type being separated from the timing indications of the second type by intervals of random durations that are unpredictable to a process, and an IO interface responsive to said timing indications of said first type and to said timing indications of said second type, for processing requests for IO operations, said IO interface buffering said request for IO operations in response to said timing indications of said second type, and buffering notifications of events related to said processing of said requests for IO operations in response to (a) said timing indications of said first type, (b) said requests for IO operations, and (c) said events related to said processing of said requests for IO operations.
Claim 33
Dependent Claim
22 words
The computer system of claim 30, wherein events relating to ones of said IO operations being unobservable are allowed to proceed unbuffered.
Claim 34
Independent Claim
147 words
A method of interfacing a service requestor and a resource allocator to restrict information flow therebetween, said method including the steps of generating timing indications of a first type and timing indications of a second type, the timing indications of the first type being separated from the timing indications of the second type by intervals of random durations that are unpredictable to the service requestor, selectively passing the generated timing indications of the first type to the service requestor, and generating a request to said resource allocator in response to said timing indications of said first type, generator a response to said service requestor in response to said request from said service requestor, and transferring said response to said service requestor in response to said response of said resource allocator and to an occurrence of a timing indication of said second type from the timing indication generator.
Claim 35
Independent Claim
147 words
A method of interfacing a service requestor and a resource allocator to restrict information flow therebetween, said method including the steps of generating timing indications of a first type and timing indications of a second type, the timing indications of the first type being separated from the timing indications of the second type by intervals of random durations that are unpredictable to the service requestor, selectively passing the generated timing indications of the first type to the service requestor, and generating a request to said resource allocator in response to said timing indications of said first type, generator a response to said service requestor in response to said request from said service requestor, and transferring said response to said service requestor in response to said response of said resource allocator and to an occurrence of a timing indication of said second type from the timing indication generator.
Claim 36
Dependent Claim
36 words
The method of claim 32 wherein said service requestor is a process, and further including the step of using said provided timing indications of said second type to schedule the initiation of processing of said process.
Claim 37
Dependent Claim
20 words
The method of claim 32 further including the step of providing the process with an imprecise representation of absolute time.
Claim 38
Dependent Claim
49 words
The method of claim 32 wherein said step of generating said timing indications includes counting timing signals to generate a timing indication of one of said first and second types when a certain count is achieved, and restarting the count with a number that is unpredictable by said process.
Claim 39
Dependent Claim
163 words
An interface for restricting information flow between a service requestor and a resource allocator, said interface including a timing indication generator that generates timing indications of a first type and timing indications of a second type, the timing indications of the first type being separated from the timing indications of the second type by intervals of random durations that are unpredictable to the service requestor, means responsive to said timing indication generator for selectively passing said timing indications of said first type to said service requestor, means in said service requestor responsive to said timing indications of said first type for generating a request to said resource allocator. means in said resource allocator responsive to said request from said service requestor for generating a response to said service requestor, means responsive to said responsive of said resource allocator and to an occurrence of a timing indication of said second type from the timing indication generator for transferring said response to said service requestor.
Claim 40
Dependent Claim
163 words
An interface for restricting information flow between a service requestor and a resource allocator, said interface including a timing indication generator that generates timing indications of a first type and timing indications of a second type, the timing indications of the first type being separated from the timing indications of the second type by intervals of random durations that are unpredictable to the service requestor, means responsive to said timing indication generator for selectively passing said timing indications of said first type to said service requestor, means in said service requestor responsive to said timing indications of said first type for generating a request to said resource allocator. means in said resource allocator responsive to said request from said service requestor for generating a response to said service requestor, means responsive to said responsive of said resource allocator and to an occurrence of a timing indication of said second type from the timing indication generator for transferring said response to said service requestor.
Claim 41
Dependent Claim
21 words
The interface of claim 36 wherein said resource allocator is a process scheduler and wherein said service requestor is a process.
Claim 42
Dependent Claim
45 words
The interface of claim 36 wherein said service requestor comprises a process and wherein said resource allocator comprises an IO interface for receiving requests from said process, said IO interface being responsive to said timing indication generator to schedule events associated with said IO interface.
Claim 43
Dependent Claim
184 words
A digital computer system for processing a plurality of processes, said system comprising a timing indication generator that generates two types of timing indications that are unpredictable to the processes, said generator also generating a running time value available to said processes, said timing indication generator comprising a tick counter for counting timing signals and for generating one of said timing indications when said tick counter has counted out, and an unpredictable number store means for re-loading said tick counter with a random number when said tick counter has counted out, means responsive to said timing indication generator for providing a partial representation of said running time value for use in the execution of the processes that is less accurate than said running time value, a scheduler responsive to the timing indications of a first one of said types for scheduling context switches between execution of respective said processes, and a request processor that responds to requests resulting from execution of said processes, and delays execution of events relating to said requests, until the occurrence of timing indications of the second of said types.
Claim 44
Dependent Claim
184 words
A digital computer system for processing a plurality of processes, said system comprising a timing indication generator that generates two types of timing indications that are unpredictable to the processes, said generator also generating a running time value available to said processes, said timing indication generator comprising a tick counter for counting timing signals and for generating one of said timing indications when said tick counter has counted out, and an unpredictable number store means for re-loading said tick counter with a random number when said tick counter has counted out, means responsive to said timing indication generator for providing a partial representation of said running time value for use in the execution of the processes that is less accurate than said running time value, a scheduler responsive to the timing indications of a first one of said types for scheduling context switches between execution of respective said processes, and a request processor that responds to requests resulting from execution of said processes, and delays execution of events relating to said requests, until the occurrence of timing indications of the second of said types.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-06-14 | 1996-12-14 | 1997-06-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-06-14 | 2000-12-14 | 2001-06-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-06-14 | 2004-12-14 | 2005-06-15 | $7700.00 | Window Closed / Lapsed |