Nec Corporation

Other

Nec Research Institute, Inc.

Kazue Sako

Jun Furukawa

Hiroshi Miyauchi

Naoya Torii

Yasutsugu Kuroda

Seiichi Domyo

Hiroyuki Ando

Hiroyoshi Tsuchiya

Joseph J Kilian

Masashi Yamazaki

Seiko Kanno

Toshiyuki Isshiki

Kengo Mori

Ichirou Morita

Isamu Teranishi

Satoshi Obana

Jun Noda

Daigo Taguchi

Ichir{overscore (o)}u M{overscore (o)}rita

An electronic transaction system includes a plurality of administration servers, a terminal, a transaction server. The plurality of administration servers provides an electronic bulletin board. The terminal writes bid data including an encrypted price to the electronic bulletin board. The transaction server gets the written bid data, decrypts the encrypted price, executes transaction using the decrypted price by Zaraba scheme.

Electronic transaction system, transaction server, verification server, method of transaction, and program

A cryptocurrency system that enables to verify the origin of a cryptocurrency is provided. A cryptocurrency system includes: at least one terminal; and a plurality of management servers configured to manage a blockchain storing a trading history in a cryptocurrency. The at least one terminal includes a trading control section, and a transmission section. The trading control section is configured to generate a transaction including a first signature for a trading content and a second signature enabling to verify a validity of a remittance source address described in the trading content. The transmission section is configured to transmit the generated transaction to the plurality of management servers.

Cryptocurrency system, terminal, server, trading method of cryptocurrency, and program

A system includes a plurality of nodes, an individual one of which transmits data to which a group signature is attached, and a plurality of management servers that are directly connected to each other. An individual one of the plurality of management servers includes a ledger for managing data received from the nodes. Addition of data to the ledger of at least one of the plurality of management servers is reflected on the ledgers of the other management servers.

System, data management method, and program

In an electronic bidding system and method, it is unnecessary to disclose to bidders a list of public keys matched to bid prices, and in which price secrecy may be proved. In a function of encryption of a bidding device, a public key is generated using a bid price and an IBE public key, based on an ID-Based Encryption (IBE) system having a bid value as an ID. IBE public key is obtained on combining a plurality of partial public keys matched to partial secret keys generated by a plural number of partial bid opening devices based on a combination condition enabling group decryption. A preset message for bidding is then encrypted. In a function of decryption of a bid opening device, a number of partial bid opening devices, which is in keeping with a satisfying number of the group decryption, perform calculations for decryption for winning bid value candidates, beginning from such candidate, the allowable bid value closest to the bid closing condition. Decrypted data obtained on combining the resulting output partial bid opening data are collated to the message for bidding to decide on winning bid value.

System and method for electronic bidding

Each participant apparatus () encrypts a plaintext by using a secret key of secret key cryptography, encrypts the encryption key by a public key, and sends the plaintext and public key to a substitution/decryption apparatus (). With this processing, the limitation on the length of a ciphertext to be processed can be eliminated. In this invention, a verifiable proof text using a public key by each substitution/decryption apparatus is verified by a verification apparatus () by using the public key. If one of a plurality of organizations to decrypt and shuffle ciphertexts has not correctly executed the operation, a third party can specify it and prove that the specified organization is unauthorized.

Mix-net system

A voting server transmits a list of plaintext and encrypted voting data obtained by encrypting the plaintext to a voter terminal, and the voter terminal a selected encrypted candidate name corresponding to the plaintext elected by the voter to an encryption server. The encryption server returns encrypted voting data obtained by re-encrypting the encrypted candidate name to the voter terminal, and the voter terminal transmits the encrypted voting data received from the encryption server for voting. Decryption of the encrypted voting data is performed by an anonymous decryption system. The voter terminal certifies the voter to an authentication server, and affixes a digital signature to the encrypted voting data based on a common-key authentication base, transmitting the same to the voting server.

Anonymous electronic voting system and anonymous electronic voting method

A anonymous decryption system, the management of which is facilitated and initialization of which is readily and reliably carried out. A shuffling management center () transmits a security parameter and common public information generated on the basis of the security parameter to decryption shuffle centers (-to-m). The decryption shuffle centers (-to-m) generate public keys and decryption keys and returns the public keys to the shuffling management center (). The shuffling management center combines the returned public key to generate an encryption public key and make the encryption key public. The shuffling management center () repeats transfer of encrypted data list to the decryption shuffle center (-j) having the j-th processing priority when it decrypts the encrypted data list, transfer of a received data list of which a order-switching process and a partial decryption process are carried out to the next decryption shuffle center (-(j+1)). Such processing is carried out for up to the last decryption shuffle center (-m) and make the data list from there the decryption result.

Anonymous decryption system, anonymous decryption method, and program

A coding function section in a bidder sub-system is supplied with a code parameter that corresponds to a bid to be offered, and the bid is coded using the code parameter. A tender opening system decodes received bids using a decode parameter corresponding to a highest or lowest bid amount in a predetermined bid range, and any bid that is successfully decoded using the decode parameter is accepted as the contract price. If no bid is decoded using the decode parameter of the highest/lowest amount of the range, the tender opening system attempts to decode all bids using the decode parameter of the next highest/lowest bid in the range. In this manner information regarding unaccepted bids is kept confidential by not publishing the decode parameters concerning the bids inferior to the winning bid.

Electronic tender system

A system allowing a participant to participate anonymously in a plurality of sessions but to be detected that the same participant has participated more than once in the same session is disclosed. The participant authorizes individual data using secret information depending on session-related information. The reception subsystem determines whether received data is anonymous participation data authorized by the participant subsystem and further determines whether anonymous signatures of arbitrary two pieces of anonymous participation data are signed by an identical participant subsystem. The anonymous signature may include data generated by raising a session-dependent base to a power dependent on the secret information.

Anonymous participation authority management system

An electronic revenue stamp issuing apparatus and a method thereof and a recording medium stored a control program thereof, in which the amount of an electronic revenue stamp that became invalid can be used again as a possible amount to issue without any communication with a specified communication center, are provided. The electronic revenue stamp issuing apparatus provides a judging means for judging whether the amount of an electronic revenue stamp to be issued is equal to or less than a possible amount to issue in which a prepaid amount is stored or not, an issuing means for issuing the electronic revenue stamp as data attached a signature of the electronic revenue stamp issuing apparatus to a message to be attached to the electronic revenue stamp, the amount of the electronic revenue stamp, and an identifier of a receiver of the electronic revenue stamp, in case that the amount of the electronic revenue stamp is equal to or less than the possible amount to issue, a balance amount reducing means for reducing the amount of the electronic revenue stamp from the possible amount to issue, when the electronic revenue stamp was issued, a verifying means, when the verifying means receives a certificate making electronic revenue stamp invalid attached a signature of the receiver, verifies whether the certificate making electronic revenue stamp invalid is valid or not by using the identifier of the receiver and the signature of the electronic revenue stamp issuing apparatus, an amount increasing means for increasing the possible amount to issue by the amount of the electronic revenue stamp made to be invalid, and an invalid electronic revenue stamp recording means for recording the certificate making electronic revenue stamp invalid that was made to be invalid.

Electronic revenue stamp issuing apparatus and method thereof and recording medium stored control program thereof

A zero-knowledge proving system includes a proving mechanism for proving equality or inequality of two discrete logarithms and a verifying mechanism for verifying said equality or inequality. The proving mechanism stores public information including a designated operation scheme, two input numbers &#x3b1; and &#x3b2;, and two predetermined bases g and h, private information x which is a discrete logarithm of &#x3b1; to the base g. After converting &#x3b1;, &#x3b2; and h to produce &#x3b1;', &#x3b2;&#x2032; and &#x3b3;&#x2032; as follows: &#x3b1;&#x2032;=&#x3b1;; &#x3b2;&#x2032;=&#x3b2;; and &#x3b3;&#x2032;=h, the equality of a log&#x3b1;&#x2032; and log&#x3b2;&#x2032; and the equality of log&#x3b1;&#x2032; and log&#x3b3;&#x2032; are proved. The verifying mechanism verifies the equality of a log&#x3b1;&#x2032; and log&#x3b2;&#x2032; and the equality of log&#x3b1;&#x2032; and log&#x3b3;&#x2032;. Then, the received &#x3b2;&#x2032; and &#x3b3;&#x2032; are checked to determine the equality or inequality thereof, and it is determined whether the proof is acceptable, depending on the verification and the check results.

Zero-knowledge proving system and method

A system and method for determining winner is capable of keep all of the voting contents secret with permitting only determination of winning or losing, and further permitting the third party to verify the determination. The system generally includes voter sub-systems for voting a voting value indicative of a selected event among a finite number of events, and a management sub-system for identifying at least one voter sub-system voted a winning value determined among the finite number of events as a winner. The voter sub-system includes encrypting parameter obtaining means for obtaining an encrypting parameter depending upon the voting value, encryption processing means for generating a cryptographic voting data by performing encrypting process on the basis of the encrypting parameter obtained by the encrypting parameter obtaining means, and transmitting means for transmitting the cryptographic voting data generated by the cryptography processing means. The management sub-system includes receiving means for receiving the cryptographic voting data until a predetermined reception time limit, decoding parameter obtaining means for obtaining decoding parameter for the winning value and retrieving means for retrieving the voting value matching with the winning value with decoding the cryptographic voting data received by the receiving means with the decoding parameter obtained by the decoding parameter obtaining means.

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Tokyo, Japan

Kazue Sako