Interference detecting ring oscillators

Patent metadata

Field	Value
Publication number	US-11068589-B2
Application number	US-201715853188-A
Country	US
Kind code	B2
Filing date	Dec 22, 2017
Priority date	Dec 22, 2017
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

A system for providing security in a computer system is provided. The system includes a plurality of ring oscillators and one or more logic circuits. The ring oscillators are equipped with a respective plurality of counters to count impulses of oscillating outputs of the ring oscillators. The one or more logic circuits start and stop the respective plurality of counters over repeated counting periods, and select a group of ring oscillators from the plurality of ring oscillators. The one or more logic circuits also determine a correlation between oscillating outputs of the group of ring oscillators. The one or more logic circuits further generate a notification indicating interference in the group of ring oscillators and thereby the plurality of ring oscillators when the correlation is above a predefined threshold correlation.

First claim

What is claimed is:

1. A system for providing security in a computer system, the system comprising:
a plurality of ring oscillators that are identical as designed but have different oscillation frequencies as manufactured, the plurality of ring oscillators being equipped with a respective plurality of counters configured to count impulses of oscillating outputs of the plurality of ring oscillators; and
one or more logic circuits configured to at least:
start the respective plurality of counters, and stop the respective plurality of counters, over repeated counting periods;
select a group of ring oscillators from the plurality of ring oscillators, the group of ring oscillators being equipped with a respective group of counters of the respective plurality of counters, wherein the one or more logic circuits configured to select the group of ring oscillators includes being configured to:
sort counter values from the respective plurality of counters, and
select the group of ring oscillators based on similarity of the counter values from the respective group of counters with which the group of ring oscillators is equipped;

determine a correlation between oscillating outputs of the group of ring oscillators based on counter values obtained from the respective group of counters over the repeated counting periods, the counter values indicating oscillation frequencies of respective ring oscillators of the group of ring oscillators; and
generate a notification indicating interference in the group of ring oscillators and thereby the plurality of ring oscillators when the correlation is above a predefined threshold correlation.

2. The system of claim 1 , wherein the group of ring oscillators is a pair of ring oscillators, and the one or more logic circuits being configured to select the group of ring oscillators includes being configured to select the pair of ring oscillators from the plurality of ring oscillators.

3. The system of claim 1 , wherein the one or more logic circuits being configured to determine the correlation between the oscillating outputs of the group of ring oscillators includes being configured to determine a difference between the counter values from the respective group of counters, and
wherein the one or more logic circuits being configured to generate the notification includes being configured to generate the notification when the difference between at least a predefined portion of the counter values from the respective group of counters is below a predefined threshold difference that indicates the correlation is above the predefined threshold correlation.

4. The system of claim 3 , wherein the one or more logic circuits being configured to determine the correlation includes being configured to:
generate a sequence of bit values for the group of ring oscillators based on the counter values from the respective group of counters, each bit value of the sequence indicating whether the difference between a pair of the counter values from the respective group of counters is above or below the predefined threshold difference; and
apply a filter to the sequence to generate a filter value that indicates the correlation.

5. The system of claim 3 , wherein the one or more logic circuits being configured to determine the difference includes being configured to perform arithmetic subtraction or exclusive-or operations on the counter values from the respective group of counters.

6. The system of claim 1 , wherein the one or more logic circuits being configured to select the group of ring oscillators includes being configured to select multiple groups of ring oscillators from the plurality of ring oscillators,
wherein the one or more logic circuits being configured to determine the correlation includes being configured to determine correlations between the oscillating outputs of the multiple groups of ring oscillators, and
wherein the one or more logic circuits being configured to generate the notification includes being configured to generate the notification when any of the correlations is above the predefined threshold correlation.

7. The system of claim 1 , wherein the one or more logic circuits being configured to generate the notification includes being configured to generate a visual or audible notification, or cause the computer system to shut down or reset.

8. A system for providing security in a computer system, the system comprising:
a plurality of ring oscillators that are identical as designed but have different oscillation frequencies as manufactured, the plurality of ring oscillators being equipped with a respective plurality of counters configured to count impulses of oscillating outputs of the plurality of ring oscillators; and
one or more logic circuits configured to at least:
start the respective plurality of counters, and stop the respective plurality of counters, over repeated counting periods;
select a group of ring oscillators from the plurality of ring oscillators, the group of ring oscillators being equipped with a respective group of counters of the respective plurality of counters, wherein the one or more logic circuits configured to select the group of ring oscillators further includes being configured to:
cluster the counter values from the respective plurality of counters into one or more clusters of counter values based on similarity of the counter values, and
select a cluster of the one or more clusters that includes the counter values from the respective group of counters with which the group of ring oscillators is equipped;

determine a correlation between oscillating outputs of the group of ring oscillators based on counter values obtained from the respective group of counters over the repeated counting periods, the counter values indicating oscillation frequencies of respective ring oscillators of the group of ring oscillators; and
generate a notification indicating interference in the group of ring oscillators and thereby the plurality of ring oscillators when the correlation is above a predefined threshold correlation.

9. The system of claim 8 , wherein the group of ring oscillators is a pair of ring oscillators, and the one or more logic circuits being configured to select the group of ring oscillators includes being configured to select the pair of ring oscillators from the plurality of ring oscillators.

10. The system of claim 8 , wherein the one or more logic circuits being configured to generate the notification includes being configured to generate a visual or audible notification, or cause the computer system to shut down or reset.

11. A method implemented by a system for providing security in a computer system, the system comprising a plurality of ring oscillators that are identical as designed but have different oscillation frequencies as manufactured, the plurality of ring oscillators being equipped with a respective plurality of counters configured to count impulses of oscillating outputs of the plurality of ring oscillators, the method comprising:
starting the respective plurality of counters, and stopping the respective plurality of counters, over repeated counting periods;
selecting a group of ring oscillators from the plurality of ring oscillators, the group of ring oscillators being equipped with a respective group of counters of the respective plurality of counters, wherein selecting the group of ring oscillators includes:
sorting counter values from the respective plurality of counters, and
selecting the group of ring oscillators based on similarity of the counter values from the respective group of counters with which the group of ring oscillators is equipped;

determining a correlation between oscillating outputs of the

Assignees

• Boeing Co

Inventors

• Hars Laszlo

Classifications

• H03K3/0315

  Ring oscillators · CPC title

• G06F7/588 Primary

  Random number generators, i.e. based on natural stochastic processes · CPC title

• G06F21/71

  to assure secure computing or processing of information · CPC title

• G06F2221/034

  Test or assess a computer or a system · CPC title

• G06F21/554 Primary

  involving event detection and direct action · CPC title