Mitsubishi Electric Corporation

Yoshihiro Koseki

Yutaka Kawai

Takato Hirano

Satoshi Yasuda

Yoichi Shibata

Takashi Ito

Nori Matsuda

Mitsuhiro Hattori

Takumi Mori

Ryo Hiromasa

Kenichiro Hayasaka

A searchable encryption system includes a registration device including an index generation unit () and an encrypted index generation unit (). The index generation unit () generates a registration keyword index by using a registration keyword, authorized-person attribute information corresponding to an authorized person who has an authority to search for the registration keyword, a user key function to generate a user key corresponding to a searcher, a search query function to generate a search query having the user key incorporated therein, and an index query function to generate an index query having the search query incorporated therein. The encrypted index generation unit () generates an encrypted index by encrypting the registration keyword index by using the index disclosure key.

Searchable encryption system, searchable encryption method, and non-transitory computer-readable recording medium

A registration device () generates ciphertext data using a new data key, generates an encrypted keyword using a new keyword key, and registers a set of the ciphertext data and the encrypted keyword. A search operation device () restores an old data key from the new data key, restores an old keyword key from the new keyword key, and generates a new search query and an old search query, using the new keyword key and the old keyword key, respectively. A data management device () finds an encrypted keyword that matches one of the new search query and the old search query, and outputs an encrypted search result including ciphertext data corresponding to the encrypted keyword that has been found. The search operation device decrypts a plaintext from the ciphertext data included in the encrypted search result, using one of the new data key and the old data key.

Searchable encryption system

A registration device () accepts plaintext, attribute information of a user having an authority of referring to the plaintext, and a registration key for use in generating a user key for generating a search query. The registration device generates aggregate information indicating one or more aggregate values, by aggregating a plurality of attribute values included in the attribute information. The registration device generates generalized information indicating a plurality of generalized values for each aggregate value by generalizing each aggregate value included in the aggregate information. The registration device generates ciphertext data including the plaintext encrypted, by using the plaintext, the attribute information, the generalized information, and the registration key. The registration device registers the ciphertext data in a database.

Registration device, search operation device, and data management device

A registration device () generates an encryption keyword by encrypting a keyword with a registration key, generates an index including the encryption keyword and identification information which identifies a corresponding ciphertext, generates a conversion key from the registration key and a search key, and registers a plurality of ciphertexts, the index, and the conversion key in a server device (). A search device () generates a search query by encrypting a keyword, and transmits the search query to the server device (). The server device () generates a re-encryption keyword by re-encrypting the search query with the registered conversion key, searches the registered index with the re-encryption keyword, acquires, from the index, the identification information if the encryption keyword is obtained as a search result, extracts a ciphertext identified by the identification information from the registered plurality of ciphertexts, and transmits the extracted ciphertext to the search device ().

Registration device, server device, searchable encryption system, and searchable encryption method

A cryptographic system comprising an encryption device to generate a ciphertext; a master re-encryption key generation device to generate a master re-encryption key that cannot decrypt a ciphertext generated by the encryption device, but can generate a re-encryption key for changing an access range for a ciphertext generated by the encryption device; re-encryption device to generate a re-encryption key for re-encrypting a target ciphertext generated by the encryption device, using the master re-encryption key, and re-encrypts the target ciphertext to generate a re-encrypted ciphertext, using the generated re-encryption key; and a decryption device to decrypt at least one of the ciphertext generated by the encryption device and the re-encrypted ciphertext generated by the re-encryption device.

Re-encryption device, method and computer readable medium to change the access range for ciphertext

An encryption device () generates a ciphertext ct encrypted from information x with using an encryption token etk. A decryption key generation device () generates a decryption key dk from a user secret key sk in which a vector y is set, with using a decryption token dtk corresponding to the encryption token etk. A privacy-preserving analysis device () decrypts the ciphertext ct generated by the encryption device (), by means of the decryption key dk generated by the decryption key generation device (), so as to generate a result of computation over the vector x and the vector y.

Privacy-preserving analysis device, privacy-preserving analysis system, privacy-preserving analysis method, and computer readable medium

A key acquisition unit () acquires a decryption key skin a pair of a conversion source and a public key pkin a pair of a conversion target, out of a plurality of pairs of a decryption key and a public key. A conversion key generation unit () encrypts the decryption key skacquired by the key acquisition unit () with the public key pk, so as to generate a conversion key rkfor converting a ciphertext encrypted with a public key pkin the pair of the conversion source into a converted ciphertext that can be decrypted with a decryption key skin the pair of the conversion target. An output unit () outputs the conversion key rkgenerated by the conversion key generation unit ().

Conversion key generation device, ciphertext conversion device, privacy-preserving information processing system, conversion key generation method, ciphertext conversion method, and computer

A search device () determines whether or not an auxiliary tag AT corresponding to an auxiliary query AQ obtained by conversion of a keyword exists, among auxiliary tags AT stored in an auxiliary tag storage unit () and obtained by conversion of a search word. When it is determined that the auxiliary tag AT corresponding to the auxiliary query AQ exists, the search device () specifies an encryption tag ET corresponding to a search query SQ being set with attribute information x indicating an attribute of a user, and the keyword, among encryption tags ET stored in an encryption tag storage unit () and being set with an access condition v indicating an accessible attribute, and the search word.

Search device, tag generation device, query generation device, searchable encryption system and computer readable medium

A key generation device generates a decryption key dkhaving a tag-added decryption key and a decryption key adk. The tag-added decryption key includes a decryption key tdkin which a key attribute x is set and a tag tgrequired to decrypt a ciphertext with the decryption key tdk. In the decryption key adk, the key attribute x is set. An encryption device generates an original ciphertext octin which a ciphertext attribute y corresponding to the key attribute x is set and which can be decrypted with the tag-added decryption key. A re-encryption key generation device encrypts the decryption key tdkby an attribute-based encryption scheme using a ciphertext attribute y', so as to generate a re-encryption key rkwhich is a key for generating a re-encrypted ciphertext rctwhich can be decrypted with a decryption key adkin which a key attribute x&#x2032; corresponding to the ciphertext attribute y&#x2032; is set.

Re-encryption key generation device, re-encryption device, re-encrypted ciphertext decryption device, and cryptographic system

A registration apparatus generates a data random number tuple R that is a tuple of random numbers whose quantity is the same as a level quantity L of a hierarchy that a user attribute forms, and that is also a tuple of uniformly random numbers. Also, the registration apparatus accepts a plaintext M and attribute information B. The registration apparatus executes a function F_2 by taking as input a concatenated value of an attribute value of each level j in the attribute information B and a number of each level j, executes a function F_3 by taking as input a function value of the function F_2, calculates an attribute element C_{j, 0, 0} that is an exclusive-or of a function value of the function F_3 and a jth random number of the data random number tuple R, executes a function F_4 by taking as input the plaintext M and an exclusive-or of the data random number tuple R, and generates encrypted data C that includes the attribute element C_{j, 0, 0} and a ciphertext C_{L+1} which is a function value of the function F_4. Then, the registration apparatus registers the encrypted data C in a data management apparatus.

Registration apparatus, search operation apparatus, data management apparatus

A registration terminal registers a set of a key and a ciphertext in which an access range is set and in which the key K is encrypted in a key server, and registers a tag for searching generated from the key and a keyword for searching in a search server. A search terminal acquires a ciphertext in which an access range whose range for permitting access includes an attribute is set, and decrypts the ciphertext with a decryption key in which the attribute is set, so as to generate a key. The search terminal generates a trapdoor for searching from the key and a keyword for searching, and transmits the trapdoor to the search server to acquire data corresponding to the keyword.

Registration terminal, key server, search system, and computer readable medium

A search device () transmits a search condition to a management device () that manages a numerical value which is a number sequence of one or more digits, based on a digit-by-digit correspondence between a number of each digit of the numerical value and a digit representation which is a symbol representing a digit. A grouping unit performs grouping on a plurality of search-target numerical values to be searched for, each of which is a number sequence of one or more digits, on a basis of commonality of the number of digits and commonality of a number sequence from a most significant digit, so as to generate one or more numerical value groups. A search condition generation unit generates, for each numerical value group, a search condition element by establishing a correspondence between a number of each digit of a sequence common range, which is a range of a number sequence common to search-target numerical values included in each numerical value group, and the digit representation of each digit of the sequence common range, and generates the search condition by integrating the search condition element of each numerical value group. A transmission unit () transmits the search condition generated by the search condition generation unit to the management device ().

Search device, search system, search method, and computer readable medium

A registration destination determination device () determines which data management device, among a plurality of data management devices (A,B), is to manage registration data, such that, with a data type constituting the registration data as a target type, an appearance frequency distribution of values set for the target type of the registration data managed by each of the plurality of data management devices (A,B) is different from an appearance frequency distribution of values set for the target type of the registration data managed by the whole of the plurality of data management devices (A,B).

Registration destination determination device, searchable encryption system, destination determination method, and computer readable medium

A management apparatus () stores encrypted tags (C(D)) and encrypted data such that they are associated with each other. When a search apparatus () obtains a search keyword (s) for searching for encrypted data stored in the management apparatus (), the search apparatus () calculates deterministic information (t) which is uniquely determined by the search keyword (s), and generates a search query (Q(s)) by performing encryption of a probabilistic encryption scheme on the search keyword (s) using the deterministic information (t). The search apparatus () transmits the search query (Q(s)) to the management apparatus (). When the management apparatus () receives the search query (Q(s)) from the search apparatus (), the management apparatus () determines whether the search keyword (s) obtained by decrypting the search query (Q(s)) matches an associated keyword obtained by decrypting an encrypted tag (c) stored in the management apparatus ().

Secret search system, secret search method, and computer readable medium

An encryption device () includes an encryption unit (), a detection element generation unit (), and a transmission unit (). The encryption unit () encrypts a plain text by using one of a pair of keys to generate an encrypted text into which the plain text has been encrypted and which can be subjected to homomorphic computation. The detection element generation unit () generates a detection element E used to detect a change in the encrypted text by using the one key and the encrypted text. The transmission unit () transmits the encrypted text and the detection element.

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Tokyo, Japan

Yoshihiro Koseki