# Kenji Ohkuma, Kanagawa JP

## Kenji Ohkuma, Kanagawa JP

Patent application number | Description | Published |
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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 |

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 |