# Katsuyuki Takashima, Tokyo JP

## Katsuyuki Takashima, Tokyo JP

Patent application number | Description | Published |
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20090285386 | Apparatus for Generating Elliptic Curve Cryptographic Parameter, Apparatus for Processing Elliptic Curve Cryptograph, Program for Generating Elliptic Curve Cryptographic Parameter, and Program for Processing Elliptic Cryptograph - A prime number generation unit | 11-19-2009 |

20100104094 | CIPHERTEXT GENERATING APPARATUS, CRYPTOGRAPHIC COMMUNICATION SYSTEM, AND GROUP PARAMETER GENERATING APPARATUS - The random number generating unit | 04-29-2010 |

20100275028 | VERIFICATION APPARATUS - In an integer partitioning process S | 10-28-2010 |

20100329454 | ENCRYPTION PARAMETER SETTING APPARATUS, KEY GENERATION APPARATUS, CRYPTOGRAPHIC SYSTEM, PROGRAM, ENCRYPTION PARAMETER SETTING METHOD, AND KEY GENERATION METHOD - A sophisticated cryptographic system is realized without using a pairing operation on a composite order. A random matrix selection unit | 12-30-2010 |

20120045056 | CRYPTOGRAPHIC PROCESSING SYSTEM - It is aimed to implement a hierarchical predicate encryption (HPE) scheme. A cryptographic process is performed using dual vector spaces (dual distortion vector spaces (DDVS)) of a space V and a space V* paired through a pairing operation. An encryption device generates as a cipher vector a vector in the space V, the vector having transmission information embedded therein. A decryption device, using a predetermined vector in the space V* as a key vector, performs the pairing operation on the cipher vector generated by the encryption device and the key vector, to decrypt the cipher vector and to extract information concerning the transmission information. | 02-23-2012 |

20120207299 | DATA PROCESSING DEVICE - A certification device | 08-16-2012 |

20120284530 | CRYPTOGRAPHIC PROCESSING SYSTEM, KEY GENERATION DEVICE, KEY DELEGATION DEVICE, ENCRYPTION DEVICE, DECRYPTION DEVICE, CRYPTOGRAPHIC PROCESSING METHOD, AND CRYPTOGRAPHIC PROCESSING PROGRAM - It is an object of this invention to implement a predicate encryption scheme with delegation capability. A cryptographic process is performed using dual vector spaces (dual distortion vector spaces) of a space V and a space V* paired through a pairing operation. An encryption device generates as a cipher vector a vector in which transmission information is embedded, the cipher vector being the vector of the space V. Using a predetermined vector of the space V* as a key vector, a decryption device performs the pairing operation on the cipher vector generated by the encryption device and the key vector to decrypt the cipher vector and to extract information concerning the transmission information. | 11-08-2012 |

20120324240 | SECURE SEARCH SYSTEM, PUBLIC PARAMETER GENERATION DEVICE, ENCRYPTION DEVICE, USER SECRET KEY GENERATION DEVICE, QUERY ISSUING DEVICE, SEARCH DEVICE, COMPUTER PROGRAM, SECURE SEARCH METHOD, PUBLIC PARAMETER GENERATION METHOD, ENCRYPTION METHOD, USER SECRET KEY GENERATION METHOD, QUERY ISSUING METHOD, AND SEARCH METHOD - In a secure search system to be used by a plurality of users, the size of a ciphertext is reduced and the need to generate a new ciphertext when a new user is added is eliminated. A public parameter generation device | 12-20-2012 |

20130028415 | CRYPTOGRAPHIC PROCESSING SYSTEM, KEY GENERATION DEVICE, ENCRYPTION DEVICE, DECRYPTION DEVICE, SIGNATURE PROCESSING SYSTEM, SIGNATURE DEVICE, AND VERIFICATION DEVICE - The object is to provide a secure functional encryption scheme having a large number of cryptographic functions. An access structure is constituted by applying the inner-product of attribute vectors to a span program. The access structure has a degree of freedom in design of the span program and design of the attribute vectors, thus having a large degree of freedom in design of access control. A secure functional encryption process having a large number of cryptographic functions is implemented by employing the concept of secret sharing for the access structure. | 01-31-2013 |

20130039489 | CRYPTOGRAPHIC PROCESSING SYSTEM, KEY GENERATION DEVICE, KEY DELEGATION DEVICE, ENCRYPTION DEVICE, DECRYPTION DEVICE, CRYPTOGRAPHIC PROCESSING METHOD, AND CRYPTOGRAPHIC PROCESSING PROGRAM - It is an object of this invention to implement a predicate encryption scheme with delegation capability. A cryptographic process is performed using dual vector spaces (dual distortion vector spaces) of a space V and a space V* paired through a pairing operation. An encryption device generates as a cipher vector a vector of the space V, the cipher vector being a vector in which transmission information is embedded. Using a predetermined vector of the space V* as a key vector, a decryption device performs the pairing operation on the cipher vector generated by the encryption device and the key vector to decrypt the cipher vector and to extract information concerning the transmission information. In particular, the encryption device and the decryption device perform the cryptographic process without using some dimensions of the space V and the space V*. | 02-14-2013 |

20130173929 | CRYPTOGRAPHIC PROCESSING SYSTEM, KEY GENERATION DEVICE, ENCRYPTION DEVICE, DECRYPTION DEVICE, CRYPTOGRAPHIC PROCESSING METHOD, AND CRYPTOGRAPHIC PROCESSING PROGRAM - The object is to provide a secure functional encryption scheme having many cryptographic functions. An access structure is constituted by applying the inner-product of attribute vectors to a span program. The access structure has a degree of freedom in design of the span program and design of the attribute vectors, thus having a large degree of freedom in design of access control. A functional encryption process is implemented by imparting the access structure to each of a ciphertext and a decryption key. | 07-04-2013 |

20130322627 | SIGNATURE PROCESSING SYSTEM, KEY GENERATION DEVICE, SIGNATURE DEVICE, VERIFICATION DEVICE, SIGNATURE PROCESSING METHOD, AND SIGNATURE PROCESSING PROGRAM - The object is to provide an attribute-based signature scheme which is flexible in the design and which supports a non-monotone predicate. An access structure is constituted by applying the inner-product of the attribute vectors to a non-monotone span program. This access structure is flexible in the design of the span program and in the design of the attribute vectors, providing high flexibility in the design of access control. By incorporating the concept of secret distribution in the access structure, the attribute-based signature scheme which supports the non-monotone predicate is realized. | 12-05-2013 |

20130336474 | CRYPTOGRAPHIC PROCESSING SYSTEM, KEY GENERATION DEVICE, ENCRYPTION DEVICE, DECRYPTION DEVICE, KEY DELEGATION DEVICE, CRYPTOGRAPHIC PROCESSING METHOD, AND CRYPTOGRAPHIC PROCESSING PROGRAM - Hierarchical predicate encryption (HPE) for inner products with enhanced efficiency of operations. A cryptographic processing system includes a key generation device, an encryption device, and a decryption device. The key generation device generates, as a decryption key sk | 12-19-2013 |

20130339754 | CRYPTOGRAPHIC PROCESSING SYSTEM, KEY GENERATION DEVICE, ENCRYPTION DEVICE, DECRYPTION DEVICE, CRYPTOGRAPHIC PROCESSING METHOD, AND CRYPTOGRAPHIC PROCESSING PROGRAM - A decentralized multi-authority functional encryption according to which the security of the whole system does not depend on a single party. Among a plurality of key generation devices, arbitrary one key generation device generates gparam, and each key generation device generates an authority public key and an authority secret key based on gparam. At least some key generation devices among the plurality of key generation devices generate a part of a decryption key of the user based on the authority secret key ask. The user forms one decryption by putting together the decryption keys generated by at least some of the key generation devices, and decrypts a ciphertext. | 12-19-2013 |

20140298028 | CRYPTOGRAPHIC PROCESSING SYSTEM, CRYPTOGRAPHIC PROCESSING METHOD, CRYPTOGRAHPIC PROCESSING PROGRAM, AND KEY GENERATION DEVICE - A cryptographic processing system and method to decrease the sizes of public parameters and a master secret key, and shorten the time taken for the generation process of the secret key to be supplied to the user and the encryption process. A generation device generates a basis B and a basis B* that form public parameters and a master secret key using a sparse matrix in which each row and each column have at least one value other than 0. An encryption device generates a vector in the basis B, the vector being embedded with predetermined information, as a cipher vector. A decryption device, by treating a predetermined vector in the basis B* as a key vector, conducts a pairing operation for the cipher vector and the key vector, to decrypt the cipher vector. | 10-02-2014 |

20140310521 | ENCRYPTED DATA MANAGEMENT DEVICE, ENCRYPTED DATA MANAGEMENT METHOD, AND ENCRYPTED DATA MANAGEMENT PROGRAM - An invalidation scheme of a secret key is implemented, which is usable for a functional encryption scheme. In a cryptographic processing system | 10-16-2014 |