Oscillators – Electrical noise or random wave generator
Reexamination Certificate
2002-07-29
2003-12-23
Kinkead, Arnold (Department: 2817)
Oscillators
Electrical noise or random wave generator
C331S046000, C708S250000, C708S251000, C714S739000, C327S164000
Reexamination Certificate
active
06667665
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a circuit configuration for generating random numbers, and relates in particular the layout of the circuit for a random number generator on an integrated circuit.
The generation of random numbers is of great importance for many areas of science and technology. Thus, random numbers are required for numerous applications in statistics as well as for cryptographic purposes. It is precisely cryptography that is increasingly gaining in importance in the course of the propagation of data networks and the associated security problems. Therefore, the automatic generation of random numbers constitutes an important area in electrical engineering and electronics, especially in data processing. Not only the generation of random numbers but also the quality thereof is important. Not all methods can generate random numbers which are equally “random”. Rather, it is usually possible, precisely when analyzing a large number of random numbers which have been generated by a specific random number generator, to identify patterns which lead to a deviation from the ideal, random distribution of the generated numbers. A measure of the quality of random numbers is their entropy, as described by Shannon-in “A Mathematical Theory of Communication”, The Bell System Technical Journal, vol. 27, p. 379 (1948).
A method of generating random numbers which is known in the prior art is done by sampling a signal having a high frequency with a second signal having a significantly lower frequency. These signals are thus voltages which are present at specific outputs and oscillate back and forth between two amplitude values and do this at a specific rate in the temporal profile. The sampling is effected in a special circuit into which both signals are fed. In this case, a specific point in the wave profile of the second signal is always used in order to determine an instant at which the first signal is sampled, that is to say the value of the signal (for example measured as voltage) is ascertained and converted into a numerical value.
In digital circuits, these are in the simplest case the values zero or one, for example as “one” if, at the sampling instant, the wave course of the first signal is situated above the mean value (for example 0 volts), and as “zero” if the wave course is situated below the mean value. However, it is equally possible to make continuous interpretation of the value obtained in order thus to obtain an analog number (for example a voltage in millivolts which is converted 1:1 as number).
In the case of ideal wave courses of the two signals, it would be possible to observe a periodicity in the sampling of the amplitude values, which results from the ratio of the two frequencies. Consequently, it would not be possible to generate genuine random numbers with the aid of such a random number generator. In practice, however, the waves of the two signals are not ideal wave courses, rather, precisely in the microelectronic field, an inaccuracy is generated in the wave course due to an unavoidable noise. This can have the effect that a well functioning random number generator could be achieved with as few as two simple predetermined frequencies, if the signals were independent of one another.
In practice, however, such a simple random number generator does not satisfy the high requirements made of the quality of the random number to be generated. This is because it is of essential importance for the quality of the random numbers that the two signals are independent of one another. This means that one signal does not lead to influencing of the other signal through electrical signal paths situated in the circuit used, so that the two signals are coupled to one another in a specific manner.
In so-called physical noise generators which correspond to the above principle, an attempt is made to solve this problem of the-independence of the two signals for example-by virtue of the signal to be sampled, that is to say the first signal, having a non-constant frequency. Such a signal to be sampled can be obtained for example by integrating into the circuit for generating the random numbers a so-called voltage-coupled oscillator (voltage controlled oscillator, VCO) whose control input is fed by a periodically varying signal, as is provided by a second oscillator, for example. As a result, this has the effect that the frequency of the signal of the VCO is modulated in a manner dependent on the wave course of the second oscillator. In this case, the second oscillator may also be a VCO which is operated with a constant voltage for example at its control input, so that an oscillation signal having a constant frequency is output at its signal output. However, this approach, too, has still not led to satisfactory results for all areas of use. As a result, it can happen that the two signals are temporarily coupled, so that a mixed frequency is formed provided that the frequency of the first signal is suitable for such coupling at a specific point in time and the two signals diverge from one another again after a specific time. As a result, the quality of the random numbers provided by the circuit fluctuates with the varying frequency of the first signal. Consequently, there is still a need for random number generators in which the quality of the random numbers generated is better.
German Patent No. DD 279 763 A1 describes a method for generating random numbers in microcomputers, in which two non-correlated electrical oscillations are utilized whose frequencies differ at least by the factor 100. The oscillations are generated by two independent sources, to be precise in such a way that there is correlation neither between the frequencies nor between the phase angles of the two oscillations. The oscillations of the higher frequency are counted by a counter started by a microcomputer, and the oscillation of the lower frequency is utilized to stop the counter. The random number is then available, after the stopping of the counter, as counter reading for further processing.
U.S. Pat. No. 5,859,450 describes a guard ring which is provided for reducing the dark current of a photodiode. What is involved in this case is an annular highly doped region in semiconductor material, which, according to the description in column 4 of U.S. Pat. No. 5,859,540, changes the position of the depletion zone and thus reduces the dark current. A guard ring is generally a doped region in semiconductor material which surrounds a component for the purpose of current delimitation.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a random number generator which overcomes the above-mentioned disadvantages of the heretofore-known random number generators of this general type and which provides an improved independence of the two signals.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration, including:
an integrated circuit;
a random number generator configuration provided on the integrated circuit;
the random number generator configuration including a first clock generator circuit for generating a first signal having one of a first frequency and a first frequency range with a first mean value, and the random number generator configuration including a second clock generator circuit for generating a second signal having one of a second frequency and a second frequency range with a second mean value, the first and second clock generator circuits generating the first and second signals such that one of the second frequency and the second mean value is smaller than one of the first frequency and the first mean value;
the first clock generator circuit having a first voltage supply, the second clock generator circuit having a second voltage supply;
the random number generator configuration including a generator configured to sample the first signal with the second signal and configured to generate at least one random number in dependence of a sampling result; and
the ran
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