Cryptography – Key management – Having particular key generator
Reexamination Certificate
2000-02-24
2004-09-07
Morse, Gregory (Department: 2134)
Cryptography
Key management
Having particular key generator
C380S263000, C708S250000, C708S251000, C708S252000
Reexamination Certificate
active
06788787
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pseudorandom number generator that generates a chaotic stream of pseudorandom numbers, to a method for stream encrypting, and to a stream encrypting communication method.
2. Description of the Related Art
With the widespread application of digital computers, networks connecting computers have exhibited rapid development, bringing with it the need to transfer huge quantities of information, and multi-user communication is expected to be able to meet this need.
The purpose of achieving widespread use of multi-user communication is to achieve reliable transfer of huge amounts of information and to reap the benefits of sharing single communication circuit. Beyond this purpose, however, there are also the aims of achieving a robust social infrastructure, preventing unauthorized access, and assuring confidentiality.
In next-generation multi-user communication systems, CDMA (code division multiple access) systems, making use of spectral diversity with good immunity to interference, will become the systems of choice. In such spread-spectrum systems, pseudorandom number generators will be key devices. Because noise generated by actual physical mechanisms lacks repeatability, it is not usable as a practical technology in industry. In its place, there is a need for pseudorandom number generators capable of generating diverse and repeatable binary streams that can be treated as pseudorandom numbers.
The term pseudorandom noise is used interchangeably with the term pseudorandom number. Because true pseudorandom numbers, for example, as would be generated by tossing a coin, are not repeatable, they are not applicable to industrial technologies. On the other hand, unless a series of numbers can defy prediction, it cannot not be expected to offer sufficient scrambling or dispersion. Thus, the needs of industry require that these conflicting goals be met in developing an ideal pseudorandom number generator.
In the past, an M series generated by feedback shift register circuits has been known for use as pseudorandom number generators. Because if the period of an M series is made long, it is possible to achieve a time sequence that is not much different from a true series of random numbers, these are often used in place of true random numbers.
In order to achieve sufficient communication security, it is necessary to assure that the content being communicated be invisible. For this reason, it is desirable that a pseudorandom number series be used that has a low auto-correlation and cross-correlation function. With feedback shift register circuit as used in the past, however, it was difficult to generate a large number of periodic sequences with a low auto-correlation and cross-correlation function.
A chaotic stream is known to include all frequency components, and is extremely close to representing random numbers. For this reason, it is known that, if it is possible to make a chaotic stream periodic, it could be used as pseudorandom numbers.
However, because a chaotic stream repeats diversion and conversion in an unpredictable manner, it is not usable as is, and requires the addition of a means for control of the chaotic stream.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention, in view of the above-described background, to provide a pseudorandom number based on a chaotic stream that includes all frequency components, which uses a novel concept of non-linear quantizing, in which decimal parts are discarded so as to achieve integer scaling. The result being control of the chaotic stream so as to achieve generation of a large number of types of time series with low auto-correlation and cross-correlation functions,
Another object of the present invention is to provide a method for stream encrypting, which uses a binary stream obtained from a pseudorandom number generator to generate, for use, for example, in communication, encrypted text that achieves an optimal high level of security.
It is yet another object of the present invention to provide a stream encrypting communication method using an encrypted text code obtained from a stream encrypting method that enables stream encrypted communication with an extremely high level of security.
To achieve the above-noted objects, a first aspect of the present invention includes a one dimensional mapping circuit for generating chaos having non-linear input-output characteristics, an AD converter for converting an analog output of the one dimensional mapping circuit, a sample-and-hold circuit for holding and outputting a digitally converted value from the AD converter in response to an external clock, and a DA converter for outputting an analog converted value in response to the output of the sample-and-hold circuit as feedback to the one dimensional mapping circuit, (forming a chaos-generating loop), wherein the quantizing divisions of at least one of the AD converter and the DA converter are made non-linear, and a binary sequence is output responsive to the output of the sample-and-hold circuit.
According to this aspect of the present invention, with the one dimensional mapping circuit (with non-linear input-output characteristics) forming a chaos-generating loop via a sample-and-hold circuit and the like, a mapping function whereby chaos is generated is provided. By using the AD converter or the DA converter (hereinafter collectively referred to as the non-linear quantizer), the input-output characteristics of this one dimensional mapping circuit having self-feedback (the mapping at each step is suppressed), a periodic time series may be obtained from the generated chaos. The output of the sample-and-hold circuit is applied, for example, to a general decoder, and a binary sequence {Y(t)−t} is extracted from the decoder output, where t is the discrete time.
If the chaos contains all frequency components, and non-linear quantizing is used to observe its internal condition, the chaos is converted to a multiple-value integer sequence, which encompasses all combinations of integer sequences. By including a non-linear quantizer within the chaos-generating loop, it is possible to simultaneously extract the period and random numbers, and it is intrinsically guaranteed to be possible to extract all combinations thereof.
A second aspect of the present invention is a variation of the first aspect, wherein the pseudorandom number generator has an AD converter with linear quantizing divisions and a DA converter with non-linear quantizing divisions.
According to the second aspect of the present invention, by using an AD convener with linear quantizing divisions and DA converter with non-linear quantizing divisions, it is possible to broaden the dynamic range of the one dimensional mapping circuit.
A third aspect of the present invention is a variation on the pseudorandom number generator of the first aspect, wherein the one dimensional mapping circuit is implemented by a CMOS inverter, and wherein the AD converter is configured so as to include an AD weighting resistive array and a comparator array that compares the relative size of an output obtained from a synthesized resistance of the AD weighting resistive array and the analog output from the one dimensional mapping circuit. The sample-and-hold circuit is implemented as a flip-flop array that captures and holds the digital output of the AD converter in response to an external clock, and wherein the DA converter is configured so as to include a DA weighting resistive array. Further, a switching array outputs an output obtained from the synthesized resistance of the DA weighting resistive array in response to the digital output from the sample-and-hold circuit as feedback to the one dimensional mapping circuit.
According to the third aspect as described above, it is possible to implement the pseudorandom number generator using a CMOS integrated circuit.
A fourth aspect of the present invention is a variation on the pseudorandom number generator of the third aspect, wherein an exclusi
Ishihara Tetsuya
Shono Katsufusa
Ueno Osamu
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Lipman Jacob
Morse Gregory
Yazaki -Corporation
LandOfFree
Pseudorandom number generator, stream encryption method, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pseudorandom number generator, stream encryption method, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pseudorandom number generator, stream encryption method, and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3240007