1
Kazuo Ohta, Tatsuaki Okamoto: Method and apparatus for implementing electronic cash. Nippon Telegraph and Telephone Corporation, Pollock Vande Sande & Priddy, December 11, 1990: US04977595 (246 worldwide citation)

In an electronic cash implementing method, a user makes a bank apply a blind signature to user information Vi produced, by a one-way function, from secret information Si containing identification information, thereby obtaining signed user information. Further, the user makes the bank apply a blind s ...


2
Ginya Ishiguro, Toshiyasu Muta, Kazutaka Sakita, Shoji Miyaguchi, Tatsuaki Okamoto, Atsushi Fujioka: Method and apparatus for settlement of accounts by IC cards. Nippon Telegraph and Telephone Corporation, Pollock Vande Sande and Priddy, March 7, 1995: US05396558 (135 worldwide citation)

An IC card has a card information memory area wherein there are written a master public key nA, card secret keys pU and qU, a card public key nU, a card identification number IDU, and a first master digital signature SA1 for information including the card identification number. An IC card terminal h ...


3
Tatsuaki Okamoto, Kazuo Ohta: Electronic cash system. Nippon Telegraph and Telephone Corporation, Pollock VandeSande and Priddy, June 29, 1993: US05224162 (121 worldwide citation)

In an electronic cash system, K sets of blind signature information are derived from secret information containing identification information of a user, K/2 sets of them are opened and a bank attaches a blind signature to the remaining K/2 sets of information. The user obtains a signed license from ...


4
Tatsuaki Okamoto, Shoji Miyaguchi, Akira Shiraishi, Tsukasa Kawaoka: Signed document transmission system. Nippon Telegraph & Telephone Public Corporation, Pollock Vande Sande and Priddy, November 25, 1986: US04625076 (105 worldwide citation)

On the transmitting side, a signature corresponding to a document to be transmitted is generated using a random number and the document as variables and on the basis of a congruent polynomial of second or higher degree with respect to the random number, secret key information and public key informat ...


5
Tatsuaki Okamoto: Method and apparatus for implementing hierarchical electronic cash. Nippon Telegraph and Telephone Corporation, Pollock Vande Sande & Amernick, July 20, 1999: US05926548 (96 worldwide citation)

A user U generates a signature verification key N.sub.U, a signature key SS.sub.U and a cipher key K, enciphers (X,N.sub.U) by a public key into E.sub.I (X,K,N.sub.U) and sends the enciphered information to a bank together with user information U and the amount of money X. The bank registers the inf ...


6
Eiichiro Fujisaki, Tatsuaki Okamoto, Kazuo Ohta: Electronic cash implementing method using a trustee. Nippon Telegraph and Telephone, Pollock Vande Sande & Priddy, May 4, 1999: US05901229 (81 worldwide citation)

In an electronic cash implementing method using a trustee, a user registers his identification information ID.sub.U and anonymous public key N with the trustee and receives a license (B,I). The user processes the license (B,I) by a public key corresponding to the amount to be issued and sends the pr ...


7
Kazuo Ohta, Tatsuaki Okamoto: Authentication system and apparatus therefor. Nippon Telegraph & Telephone Corporation, Pollock Vande Sande and Priddy, November 6, 1990: US04969189 (80 worldwide citation)

In the case where a prover A proves the validity of a pretender B to a verifier C, B receives an initial response x' created by A, randomizes it with a random component and sends it as x", and randomizes an inquiry .beta. from C with the random component and sends it as .beta.' to A. A proves, for t ...


8
Masanori Obata, Hiroyuki Sugiyama, Moribumi Okukawa, Tatsuaki Okamoto: Method and system for depositing private key used in RSA cryptosystem. Nippon Telegraph and Telephone Corporation, Jones & Askew, June 6, 2000: US06072876 (59 worldwide citation)

A scheme for depositing a private key used in the RSA cryptosystem which is capable of maintaining the private key more safely, without requiring a user to always carry around a storage medium. In this scheme, a private key of a user is divided into a first partial private key and a second partial p ...


9
Ginya Ishiguro, Toshiyasu Muta, Kazutaka Sakita, Shoji Miyaguchi, Tatsuaki Okamoto, Atsushi Fujioka: Method and apparatus for settlement of accounts by IC cards. Nippon Telegraph and Telephone Corporation, Pollock Vande Sande & Priddy, March 26, 1996: US05502765 (51 worldwide citation)

An IC card has a card information memory area wherein there are written a master public key nA, card secret keys pU and qU, a card public key nU, a card identification number IDU, and a first master digital signature SA1 for information including the card identification number. An IC card terminal h ...


10
Hidemi Moribatake, Tatsuaki Okamoto: Electronic cash implementing method and equipment using user signature and recording medium recorded thereon a program for the method. Nippon Telegraph and Telephone Corporation, Connolly Bove Lodge & Hutz, March 25, 2003: US06539364 (34 worldwide citation)

A user registers a user public key PKU as a pseudonym at a trustee or issuer and obtains an signature for the pseudonym as a license. The sends the pseudonym, PKU identification information IdU and the amount of withdrawal x to the issuer institution. The issuer increments a balance counter of the p ...