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  Cryptographic key, encryption device, encryption/decryption device, cryptographic key management device, and decryption deviceUSPTO Application #: 20070019811Title: Cryptographic key, encryption device, encryption/decryption device, cryptographic key management device, and decryption device Abstract: A cryptographic key 1 constituted to be freely attachable and detachable to/from a personal computer 2 encrypting and decrypting data by use of a cipher key includes: a pseudo random number generator 14 for generating a pseudo random number of a chaotic time series based on a data size of the data, a chaotic function and an initial value of the chaotic function; and a USB controller 12 for receiving the data size of the data from the personal computer 2 and transmitting the pseudo random number of the chaotic time series as the cipher key to the personal computer 2, the pseudo random number being generated in the pseudo random number generator 14, when the cryptographic key 1 is attached to the personal computer 2. (end of abstract) Agent: Finnegan, Henderson, Farabow, Garrett & Dunner LLP - Washington, DC, US Inventors: Tetsuya Ishihara, Osamu Ueno, Yoshikazu Nishino, Fumiaki Nishiyama, Takumi Suzuki, Rei Isogai USPTO Applicaton #: 20070019811 - Class: 380263000 (USPTO) Related Patent Categories: Cryptography, Communication System Using Cryptography, Symmetric Key Cryptography, Symmetric Key Synchronization, Nonlinear Or Chaotic System The Patent Description & Claims data below is from USPTO Patent Application 20070019811. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to a cryptographic key having a pseudo random number generator for generating a pseudo random number of a chaotic time series, an encryption device for encrypting plaintext data by use of the pseudo random number of the chaotic time series from the cryptographic key, an encryption/decryption device for encrypting and decrypting the plaintext data, a cryptographic key management device for managing the cryptographic key, and a decryption device for decrypting cryptographic data. [0002] Recent years, a universal serial bus. (USB) has been used as an interface in which the same connector and cable are used coherently for a connection of a personal computer to relatively low-speed peripheral equipment such as a keyboard, a mouse, a speaker, a modem and a printer. In this USB, a data transfer rate between the personal computer and the peripheral equipment is, for example, 1.5 Mbps, which is relatively low-speed. [0003] There has been known an encryption device for encrypting data by use of a personal computer and peripheral equipment, which are in conformity with the standard of the USB as described above. This encryption device is constituted of a key information unit in which key information is registered, and of a personal computer having a cryptographic algorithm, to which the key information unit is attached. [0004] In the key information unit, there is a key information unit in which the key information is registered by a person at the time of purchase thereof, a key information unit in which the key information is registered at the time of shipment thereof from a factory, or the like. Upon being equipped with the key information unit, the personal computer has read out the key information from the key information unit, has created a cipher key from the key information by use of the cryptographic algorithm, and has encrypted plaintext data by use of this cipher key, thus creating cryptographic data. SUMMARY OF THE INVENTION [0005] However, since the cryptographic algorithm is resident in the personal computer in the conventional encryption device, it will be facilitated for a third party to decipher the cipher key created by the cryptographic algorithm. Therefore, the conventional encryption device has had a problem that plaintext data on a personal computer owned by a person is browsed easily by the third party. [0006] Meanwhile, in the multiuser information and communication toward the next generation, a code division multiple access (CDMA) system will become a mainstream, which uses a spread spectrum communication system excellent in confidentiality and having high performance of removing an interference wave. In this spread spectrum communication system, a pseudo random number generator capable of generating a pseudo random number will become a key device. Here, an important matter on the industrial technology is to realize a pseudo random number generator capable of generating many types of binary sequences that can be reproduced artificially and regarded as pseudo random numbers. [0007] For example, an action such as throwing a coin and shaking a dice is represented as a true random number and has no reproductivity, and thus cannot be used as an industrial technology. On the other hand, unless an unpredictable number sequence is used, a sufficient scramble or spread thereof cannot be realized. [0008] Chaos has been known as one used to meet these two conditions. The chaos contains a wave of every frequency, and the chaos and the random number are very closely related to each other. Hence, it is possible to use a periodic time series of the chaos as the pseudo random number. Therefore, an encryption processing for encrypting data by use of a pseudo random number generator for generating a pseudo random number based on the chaotic time series has been desired. [0009] An object of the present invention is to provide a cryptographic key capable of preventing the data on the personal computer owned by a person from being browsed by the third party easily by making the cryptographic algorithm difficult to be deciphered by the third party, the cryptographic algorithm using the pseudo random number generator for generating the pseudo random number of the chaotic time series. [0010] Another object of the present invention is to provide an encryption device capable of creating cryptographic data having high confidentiality by carrying out the encryption by use of the pseudo random number obtained by the pseudo random number generator owned by the cryptographic key, and to provide an encryption/decryption device and a decryption device, which are capable of decrypting the cryptographic data easily. [0011] Still another object of the present invention is to provide a cryptographic key management device capable of managing the cryptographic key. [0012] A first aspect of the present invention is a cryptographic key constituted to be freely attachable and detachable to/from an external device encrypting and decrypting data by use of a cipher key, the cryptographic key comprising: a pseudo random number generator for generating a pseudo random number of a chaotic time series based on a data size of the data, a chaotic function and an initial value of the chaotic function; and a transmission/reception control unit for receiving the data size of the data from the external device and transmitting the pseudo random number of the chaotic time series as the cipher key to the external device, the pseudo random number being generated in the pseudo random number generator, when the cryptographic key is attached to the external device. [0013] According to the first aspect of the present invention, the pseudo random number generator is provided in the cryptographic key as a separate body from the external device, and only when the encryption or the decryption is carried out, the cryptographic key is attached to the external device, and the pseudo random number of the chaotic time series is transmitted from the cryptographic key to the external device. Specifically, since the pseudo random number generator (cryptographic algorithm) is not made to reside in the external device but built in the body of the cryptographic key, it becomes difficult for the third party to decipher the pseudo random number of the chaotic time series as the cipher key. Thus, the data on the personal computer owned by a person can be prevented from being browsed by the third party. [0014] A second aspect of the present invention is the cryptographic key according to the first aspect, characterized in that the -pseudo random number generator includes: a chaos generation loop constituted by including a pair of one-dimensional map circuits for generating the chaotic function, each having non-linear input/output characteristics, a pair of CMOS switches for alternately performing opening and closing actions for paths on output sides of the respective one-dimensional map circuits in synchronization with an external clock, and a pair of feedback loops for feedbacking analog outputs of the respective one-dimensional map circuits through the respective CMOS switches to input sides of the respective one-dimensional map circuits in a crossing manner; and a pair of AD converters for converting, into digital signals, the analog outputs of the respective one-dimensional map circuits, the analog outputs being taken out through the respective CMOS switches, and the respective one-dimensional map circuits iterate mapping alternately with the elapse of a discrete time defined by the external clock in the chaos generation loop to allow the pseudo random number -generator to-output binary sequences as chaotic time series through the respective AD converters. [0015] According to the second aspect of the present invention, the respective one-dimensional map circuits iterate the mapping alternately with the elapse of the discrete time defined by the external clock in the chaos generation loop, thus allowing the pseudo random number generator to output binary sequences as chaotic time series through the respective AD converters. Both of the binary sequences taken out alternately are array data, each having a random number with "0" and "1" mixed randomly. The binary sequences arrayed in accordance with the integrated time series are obtained, thus making it possible to generate the pseudo random number of the chaotic time series. Moreover, the pair of one-dimensional circuits iterate the mapping alternately, and the analog outputs obtained by the mapping are feedbacked in the crossing manner. Therefore, divergence and convergence of the analog outputs woven by the pair of one-dimensional map circuits are combined with an initial value sensitivity particular to the chaos, thus breaking an occurrence balance of "0" and "1" of the obtained binary sequences finely. Such a swing phenomenon particular to the chaos can contribute to the improvement of robustness of a stream cipher using the chaos. [0016] A third aspect of the present invention is the cryptographic key according to the second aspect, characterized in that the pseudo random number generator further includes: a DA converter for converting an initial value given in a digital signal mode into an analog signal; and a CMOS switch for performing opening and closing actions for a path on an output side of the DA converter in synchronization with the external clock. [0017] According to the third aspect of the present invention, an applied voltage equivalent to a real number is given through the DA converter. A quantization resolution of the DA converter is being increased, and thus the types of initial values are being increased. Consequently, the types of time series which can be taken out can be increased. In the industrial technology of the chaos, the maintaining of the initial value sensitivity is an extremely important factor. The initial value sensitivity is given through the DA converter. Therefore, with regard to the pair of binary sequences with initial values different from each other as starting points, the both are not superposed on each other even if they are to be superposed while shifting phases thereof in any manner. Thus, it is made possible to obtain the time series in which both auto-correlations and a cross-correlation are sufficiently small. [0018] A fourth aspect of the present invention is the cryptographic key according to the second aspect, characterized in that at least any one of the pair of one-dimensional map circuits is constituted to be capable of adjusting the input/output characteristics of its own in accordance with an external adjustment voltage. [0019] According to the fourth aspect of the present invention, it is made possible to adjust the input/output characteristics owned by the one-dimensional map circuit from the outside. Consequently, the types of the chaotic time series that can be taken out can be further increased. [0020] A fifth aspect of the present invention is an encryption device for encrypting plaintext data by use of a cipher key, the encryption device comprising: a cryptographic key having a pseudo random number generator for generating a pseudo random number of a chaotic time series based on a data size of the plaintext data, a chaotic function and an initial value of the chaotic function; and an external device for transmitting the data size of the plaintext data to the cryptographic key upon being equipped with the cryptographic key, and for encrypting the plaintext data by use of the pseudo random number of the chaotic time series as the cipher key, the pseudo random number being sent from the cryptographic key. [0021] According to the fifth aspect of the present invention, when the cryptographic key is attached to the external device, the external device transmits the data size of the plaintext data to the cryptographic key, and encrypts the plaintext data by use of the pseudo random number of the chaotic time series as the cipher key, the pseudo random number being sent from the cryptographic key. Therefore, a similar effect to that of the first aspect is obtained, and cryptographic data having high confidentiality can be created. [0022] A sixth aspect of the present invention is the encryption device according to the fifth aspect, characterized in that the external device executes an exclusive-OR operation for the pseudo random number obtained by the pseudo random number generator and the plaintext data to encrypt the plaintext data. Continue reading... Full patent description for Cryptographic key, encryption device, encryption/decryption device, cryptographic key management device, and decryption device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Cryptographic key, encryption device, encryption/decryption device, cryptographic key management device, and decryption device patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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