# Hirofumi Muratani, Kanagawa JP

## Hirofumi Muratani, Kanagawa JP

Patent application number | Description | Published |
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20090207999 | DECRYPTION PROCESSING APPARATUS, SYSTEM, METHOD, AND COMPUTER PROGRAM PRODUCT - In a decryption processing apparatus, a decompression processing unit performs a map to pieces of compressed data included in a compressed encrypted data, thereby obtaining the pieces of the encrypted data having each of the pieces of the compressed data decompressed, the decompression map being a process of inputting the compressed data and either the final output data or the auxiliary output data and being a process of outputting the encrypted data and the auxiliary output data, a decryption processing unit performs a decryption process to each of the pieces of encrypted data, using a secret key corresponding to the public key, thereby obtaining the plain data, and a control unit controls parallel execution of the decompression process and the decryption process, and controls the decryption process performed by the decryption processing unit to the encrypted data output by the decompression processing unit, based on the decryption procedure. | 08-20-2009 |

20100046741 | APPARATUS, METHOD, AND COMPUTER PROGRAM PRODUCT FOR DECRYPTING, AND APPARATUS, METHOD, AND COMPUTER PROGRAM PRODUCT FOR ENCRYPTING - An input unit inputs encrypted data that elements of a subgroup and expressed in an affine representation. A transforming unit transforms the inputted encrypted data into projective representation data expressed in a projective representation. A plain data calculating unit subjects the projective representation data to a decrypting process previously defined by a cryptosystem, thereby calculating plain data expressed in the projective representation. | 02-25-2010 |

20100046742 | APPARATUS AND COMPUTER PROGRAM PRODUCT FOR PERFORMING DATA COMPRESSION PROCESSING USING ALGEBRAIC TORUS - An encryption processing unit executes an arithmetic operation decided in advance and outputs an arithmetic result as an element on an algebraic torus. A compressing unit outputs, when the arithmetic result is an exceptional point representing an element on the algebraic torus that cannot be compressed by a compression map for compressing an element on the algebraic torus into affine representation, a compression result obtained by compressing the arithmetic result according to the compression map and outputs, when the arithmetic result is the exceptional point, an element belonging to a specific set decided in advance that does not overlap a set to which a compression result obtained by compressing the arithmetic result, which is not the exceptional point, belongs. | 02-25-2010 |

20100046743 | APPARATUS FOR PERFORMING DATA COMPRESSION PROCESSING USING ALGEBRAIC TORUS - A compressing unit compresses an element on an algebraic torus into affine representation according to a compression map. A determining unit determines whether a target element on the algebraic torus to be compressed is an exceptional point representing an element on the algebraic torus that cannot be compressed by the compression map. The compressing unit generates, when it is determined that the target element is the exceptional point, a processing result including exceptional information indicating that the target element is the exceptional point, and generates, when it is determined that the target element is not the exceptional point, a processing result including affine representation obtained by compressing the target element according to the compression map. | 02-25-2010 |

20100046745 | ENCRYPTING APPARATUS, DECRYPTING APPARATUS, CRYPTOCOMMUNICATION SYSTEM, AND METHODS AND COMPUTER PROGRAM PRODUCTS THEREFOR - A decrypting apparatus that decrypts encrypted data that has been encrypted first data containing plain data, the encrypted data being represented by using an affine representation F_{p̂m}×F_{p̂m}̂*(where p: a prime number; m: a natural number; and ̂: exponentiation) obtains encrypted data represented in a vector format and a secret key corresponding to a public key and judges whether a vector component contained in the encrypted data is the affine representation F_{p̂m}×F_{p̂m}̂*. Further, based on the result of the judging process, the decrypting apparatus maps the vector component onto each of the members of an algebraic torus by forming a decompression map and decrypts the encrypted data mapped onto each of the members of the algebraic torus, by using the secret key, therefore obtains the plain data. | 02-25-2010 |

20100046746 | PARAMETER GENERATING DEVICE AND CRYPTOGRAPHIC PROCESSING SYSTEM - A parameter generating device includes an input receiving unit that receives a degree n of an algebraic torus T including a group G in which a cryptosystem used in a torus-compressed public key cryptosystem is defined, a size W of a finite field F, and a size S of the group G, an extension-degree determining unit that determines an extension degree m of a finite field Fp | 02-25-2010 |

20100049777 | REPRESENTATION CONVERTING APPARATUS, ARITHMETIC APPARATUS, REPRESENTATION CONVERTING METHOD, AND COMPUTER PROGRAM PRODUCT - When converting an affine representation representing a 2r-th degree algebraic torus T | 02-25-2010 |

20100063986 | COMPUTING DEVICE, METHOD, AND COMPUTER PROGRAM PRODUCT - In a computing device that calculates a square of an element in a finite field, a vector representation of the element in the finite field is accepted. The vector representation includes a plurality of elements. The computing device performs a multiplication operation on a base field using the accepted elements, and obtains a multiplication value. The multiplication operation is determined by a condition under which the element in the finite field is placed in an algebraic torus. The computing device performs an addition and subtraction operation using the obtained multiplication value and the accepted elements, and obtains a calculation result of the square of the element. The addition and subtraction operation is determined by the condition. The computing device then outputs the calculation result. | 03-11-2010 |

20120124114 | ARITHMETIC DEVICE - According to one embodiment, a representation converting unit converts a set of n elements (h | 05-17-2012 |

20120150931 | DECOMPRESSING APPARATUS AND COMPRESSING APPARATUS - According to one embodiment, a decompressing apparatus includes an input unit, a calculating unit, a first selecting unit, and a decompressing unit. The input unit inputs additional data, which is obtained based on trace expression data in which an element in a subgroup of a multiplicative group of a finite field is trace-expressed and affine expression data in which the trace expression data is affine-expressed, and the trace expression data. The calculating unit calculates a plurality of solutions of simultaneous equations derived by the trace expression data. The first selecting unit selects any of a plurality of items of affine expression data in which the element is affine-expressed based on the additional data, the affine expression data being found from the solutions. The decompressing unit decompresses the selected affine expression data to the element. | 06-14-2012 |

20120239721 | ARITHMETIC DEVICE, METHOD, AND PROGRAM PRODUCT - An arithmetic device includes an input unit inputting data that are elements of a group; a converting unit is configured, when the input data are in a second representation, to convert the input data into a first representation and to perform arithmetic operation on the converted first representation using an operand in the first representation in which at least one subcomponent is a zero element to convert the converted first representation into first converted data expressed in the first representation, and when the input data are in the first representation, to perform arithmetic operation on the input data using the operand in the first representation in which at least one subcomponent is a zero element to convert the input data into second converted data expressed in the first representation; and an operating unit that performs arithmetic processing on the first or the second converted data using secret information. | 09-20-2012 |

20130218939 | EXPONENTIATION CALCULATION APPARATUS AND METHOD FOR CALCULATING SQUARE ROOT IN FINITE EXTENSION FIELD - In a computing device that calculates a square of an element in a finite field, a vector representation of the element in the finite field is accepted. The vector representation includes a plurality of elements. The computing device performs a multiplication operation on a base field using the accepted elements, and obtains a multiplication value. The multiplication operation is determined by a condition under which the element in the finite field is placed in an algebraic torus. The computing device performs an addition and subtraction operation using the obtained multiplication value and the accepted elements, and obtains a calculation result of the square of the element. The addition and subtraction operation is determined by the condition. The computing device then outputs the calculation result. | 08-22-2013 |

20130246489 | COMPUTING DEVICE - According to an embodiment, a computing device includes a receiving unit, a calculating unit, a solving unit, a selecting unit, and a determining unit. The receiving unit is configured to receive pieces of input data indicative of elements of a subgroup of a multiplicative group in a finite field and pieces of first additional data for identifying conjugates of the respective pieces of input data. The elements are represented by traces. The calculating unit is configured to calculate a coefficient of an equation based on the pieces of input data. The solving unit is configured to obtain solutions of the equation. The selecting unit is configured to select one of the solutions as a result of computation, based on the first additional data. The determining unit is configured to determine second additional data for identifying a conjugate of the selected result of computation based on the first additional data. | 09-19-2013 |