Integrated circuit having hardware circuitry to prevent...

Details Integrated circuit having hardware circuitry to prevent... Integrated circuit having hardware circuitry to prevent...

1998-08-14

2001-12-11

Heckler, Thomas M. (Department: 2182)

Electrical computers and digital processing systems: support

Digital data processing system initialization or configuration

C713S152000

Reexamination Certificate

active

06330668

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This Invention relates to hardware designed into silicon circuitry which prevents the circuitry from being forced to operate outside of predetermined parameters. More specifically, the present invention relates to hardware circuitry which may detect over or under voltage conditions, high- or low-speed clocks, and over or under temperature conditions. The circuitry may reset or shut down the silicon circuitry in response to such detections.
2. Description of Related Art
Microcontrollers have become commonplace in today's society. Over time microcontrollers have accommodated and provided a wide variety of solutions to various problems in the electronic and automation industries. At present, microcontrollers are beginning to be placed in devices or used as devices that perform secure transfers of money, monetary equivalents and secure information.
As a result of using microcontrollers for transferring and handling secure information and data, there are people dedicated to “breaking the code” or mathematically evaluating the secure data transfers in order to determine the secrets and proprietary techniques of the secure data transfers.
Smart cards, for example, have been “attacked” by varying the frequency to the microprocessor and the coprocessor at specific times. The frequency can be increased to produce race conditions in the integrated circuit that will make the circuit operate improperly due to the limited time between rising and falling edges of the clock signal. Calculation errors may result. A calculation error resulting from such a race condition can be compared with a similar calculation made with a good/correct result to correspondingly resolve the secret key(s) associated with the calculation and thereby defeat the security of the integrated circuit.
In the area of cryptography, an important article was written entitled “On the Importance of Checking Cryptographic Protocols for Faults”, Dan Boneh, Richard A. DeMillo, Richard J. Lipton, Security and Cryptography Research Group, Bellcore, 1997(hereinafter “the Bellcore article”). The Bellcore article discusses attack techniques targeted at RSA encryption and Rabin signatures. In essence the Bellcore article indicates that from time to time hardware which performs RSA encryption calculations may introduce errors. If the errors are found or can be forced by an attacker, then the RSA code may be broken by using various algorithms. Thus, there is a need for integrated circuits which perform encryption calculations that have means for stopping or limiting the circuitry from being stressed into introducing errors into calculations.
SUMMARY OF THE INVENTION
Exemplary embodiments of the present invention overcome drawbacks of past secure microcontroller designs and integrated circuitry designs by providing hardware mechanisms which prevent a silicon circuit from operating outside its proper bounds of design. In doing so, the integrated circuit, and more particularly, the microcontroller is prevented from providing or performing an incorrect calculation result under certain conditions.
Three preferred hardware mechanisms can be incorporated into the present exemplary embodiment which will each prevent the silicon circuitry from being stressed to a point of performing an invalid task. An onboard oscillation circuit built into the silicon circuit can be used to provide a system clock and prevent race clocking conditions. An onboard temperature sensing circuit, which senses when the integrated circuit is operating outside of a predetermined temperature range, can be incorporated into the present invention to stop the integrated circuit from making an incorrect calculation due to extreme temperatures. Furthermore, a voltage sensing circuit can be incorporated into the present embodiment and sense when the voltage provided to the silicon circuit is above or below a predetermined temperature range and thereby stop the silicon circuitry from being stressed to produce an invalid or incorrect calculation result.


REFERENCES:
patent: 4593180 (1986-06-01), Narita et al.
patent: 5353350 (1994-10-01), Unsworth et al.
Boneh, Dan et al, “On the Importance of Checking Cryptographic Protocols for Faults”, Security and Cryptography Research Group, pp. 1-14.

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