US 4,977,595 AGranted

Method and apparatus for implementing electronic cash

AssigneeNippon Telegraph and Telephone Corporation

InventorsKazuo Ohta, Tatsuaki Okamoto

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Abstract

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 signature to information containing authentication information Xi produced, by a one-way function, from random information Ri, thereby obtaining signed authentication information. The user uses an information group containing the signed user information, the signed authentication information, the user information and the authentication information, as electronic cash for payment to a shop. The shop verifies the validity of the signed user information and the signed authentication information, and produces and sends to the user an inquiry. In response to the inquiry the user produces a response Yi by using secret information and random information and sends it to the shop. Having verified the validity of the response the shop accepts the electronic cash.

Claims54

Dependent claims

An electronic cash implementing method in which a bank issues electronic cash to a user, said user pays a third party with said electronic cash, and said bank settles accounts with a party who finally possesses said used electronic cash, said method comprising the following steps:

wherein said user:
(a) generates user information based on secret information containing identification information of his own, through utilization of a first one-way function;
(b) obtains signed user information by having said bank apply blind signature to information containing said user information;
(c) generates authentication information based on random information through utilization of a second one-way function;
(d) obtains signed authentication information by having said bank apply blind signature to information containing said authentication information;
(e) sends, as said electronic cash issued by said bank, electronic cash information containing said user information, said signed user information, said authentication information and said signed authentication information to said third party;
wherein said third party:
(f) verifies the validity of said signed user information and said signed authentication information contained in said electronic information received from said user;
(g) if said validity is verified, generates and sends an inquiry to said user;
wherein said user:
(h) generates a response based on at least said secret information generated by himself and said inquiry received from said third party and sends said response to said third party;
wherein said third party:
(i) verifies the validity of said response through utilization of said user information and said authentication information contained in said electronic cash information received from said user and, if said response is valid, receives said electronic cash as valid one;
(j) sends said electronic cash information, said inquiry of said third party, and said response of said user to a fourth party, as required.

11 more elements

An electronic cash implementing user system in which a bank issues electronic cash to a user and the user pays to a third party with said electronic cash, comprising:

secret information generating means for generating secret information containing identification information;
user information generating means whereby user information is produced, by use of a first one-way function, from said secret information provided from said secret information generating means;
first blind signature preprocessing means whereby information containing said user information provided from said user information generating means is subjected to one-way blind signature preprocessing to produce randomized user information;
first blind signature postprocessing means whereby signed randomized user information produced by signing said randomized user information by said bank is derandomized to obtain signed user information;
secret random information generating means for generating secret random information;
authentication information generating means whereby authentication information is produced, by use of a second one-way function, from said secret random information provided from said secret random information generating means;
second blind signature preprocessing means whereby said authentication information provided from said authentication information generating means is subjected to one-way blind signature preprocessing to obtain randomized authentication information;
second blind signature postprocessing means whereby signed authentication information produced by signing said randomized authentication information by said bank is derandomized to obtain signed authentication information;
and
response generating means whereby a response is produced by use of said secret random information in response to an inquiry from said third party.

7 more elements

Dependencies are inferred from the claim text.