초록 ▼

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

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 information U and E.sub.I in a user data base in correspondence with each other, then withdraws the amount of money X from a user's bank account and sends information (X,E.sub.I) to an electronic cash issuer together with a bank signature S.sub.B (X,E.sub.I) for the information. The issuer deciphers the enciphered information E.sub.I by a secret key to obtain the information (X,N.sub.U), then registers the information E.sub.I and the key N.sub.U in an inspection data base in correspondence with each other, and enciphers the signature S.sub.I (X,N.sub.U) attached to the key N.sub.U by the key K into E.sub.K (S.sub.I), which is sent to the user via the bank. The user deciphers the information E.sub.K by the key K to obtain the issuer signature S.sub.I and sends to a shop, as electronic cash C, information containing the key N.sub.U and the issuer signature S.sub.I. The shop verifies the validity of the issuer signature and the user signature and, if they are valid, approves payment in an amount y. The shop sends data H of communication with the user to the issuer for settlement of accounts, and the issuer makes a check to see if the key N.sub.U in the data H is registered in the inspection data base.

대표청구항 ▼

[ What is claimed is:] [12.] An electronic cash issuer apparatus for an electronic cash system which is composed of an electronic cash issuer, a bank which manages account information of a user, a user who uses electronic cash for payment, and a shop which receives a payment by electronic cash, said

[ What is claimed is:] [12.] An electronic cash issuer apparatus for an electronic cash system which is composed of an electronic cash issuer, a bank which manages account information of a user, a user who uses electronic cash for payment, and a shop which receives a payment by electronic cash, said cash issuer apparatus comprising:decipher means for deciphering enciphered information E.sub.I (X,K,N.sub.U) from the bank by a secret key SE.sub.I of a public key cryptosystem to obtain an amount of money X, user cipher key K and a user signature verification key N.sub.U ;an inspection database for registering said user signature verification key N.sub.U, said enciphered information E.sub.I (X,K,N.sub.U) and the total amount of money paid so far Y as a set;signature generating means for generating an issuer signature S.sub.I (X,N.sub.U) for said amount of money X and said user signature verification key N.sub.U ;encipher means for enciphering said issuer signature S.sub.I (X,N.sub.U) by using said user cipher key K as a key therefor;means which receives form said shop communication information H concerning payment by electronic cash, reads out of said inspection database said total amount of money used Y corresponding to said user signature verification key N.sub.U, then adds said total amount of money paid so far Y with an amount of payment y, and updates said total amount of money Y;means which makes a check to see if said updated total amount of money Y is smaller than said amount of money X, and if so, instructs said bank to transfer said amount of payment y to a bank account of shop information W contained in said received information H;a history database for recording therein said received information H; andmeans which, when said updated total amount of money Y is equal to or larger than said amount of money X, erases from said inspection database the record corresponding to said user signature verification key N.sub.U and, when said updated total amount of money Y is larger than said total amount of money Y, reads out of said inspection database said enciphered information E.sub.I (X,K,N.sub.U) corresponding to said verification key N.sub.U and sends said read-out information E.sub.I (X,K,N.sub.U) to said bank so as to trace an abuser or overspender.