Method and apparatus for implementing hierarchical electronic cash

• US 5,926,548 A
• Filed: 05/20/1997
• Issued: 07/20/1999
• Est. Priority Date: 05/29/1996
• Status: Expired due to Fees

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Okamoto, Tatsuaki
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US08/859,214
• Time in Patent Office: 791 Days
• Field of Search: 705/1, 705/26, 705/30, 705/35, 705/39, 705/40, 705/41, 705/42, 705/43, 705/44, 380/9, 380/23, 380/24, 380/25, 380/29, 380/30, 380/49, 380/50, 380/59, 235/379, 235/380
• US Class Current: 705/69
• CPC Class Codes: G06Q 20/02 involving a neutral party, e.g. certification authority, notary or trusted third party [TTP]
• CPC Class Codes: G06Q 20/06 Private payment circuits, e.g. involving electronic currency used among participants of a common payment scheme
• CPC Class Codes: G06Q 20/085 involving remote charge determination or related payment systems
• CPC Class Codes: G06Q 20/10 specially adapted for electronic funds transfer [EFT] systems; specially adapted for home banking systems
• CPC Class Codes: G06Q 20/102 Bill distribution or payments
• CPC Class Codes: G06Q 20/3678 e-cash details, e.g. blinded, divisible or detecting double spending
• CPC Class Codes: G06Q 20/3829 involving key management
• CPC Class Codes: G06Q 20/383 Anonymous user system
• CPC Class Codes: G06Q 20/40 Authorisation, e.g. identification of payer or payee, verification of customer or shop credentials; Review and approval of payers, e.g. check credit lines or negative lists
• CPC Class Codes: G06Q 40/00 Finance; Insurance; Tax strategies; Processing of corporate or income taxes
• CPC Class Codes: G06Q 40/12 Accounting
• CPC Class Codes: G07F 7/1016 Devices or methods for securing the PIN and other transaction-data, e.g. by encryption arrangements for secret communication, see H04L9/00
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

A user U generates a signature verification key N_U, a signature key SS_U and a cipher key K, enciphers (X,N_U) by a public key into E_I (X,K,N_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_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_I) to an electronic cash issuer together with a bank signature S_B (X,E_I) for the information. The issuer deciphers the enciphered information E_I by a secret key to obtain the information (X,N_U), then registers the information E_I and the key N_U in an inspection data base in correspondence with each other, and enciphers the signature S_I (X,N_U) attached to the key N_U by the key K into E_K (S_I), which is sent to the user via the bank. The user deciphers the information E_K by the key K to obtain the issuer signature S_I and sends to a shop, as electronic cash C, information containing the key N_U and the issuer signature S_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_U in the data H is registered in the inspection data base.

Claims

1. An electronic cash implementing method 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 method comprising:

step (1) wherein said electronic cash issuer opens an encipher function E₁ and a signature verification function V₁ to the public;

step (2) wherein said user sends to said bank user information U and a face value X for requesting said bank to withdraw an amount of money X from his bank account and issue electronic cash of said face value X, while at the same time said user generates a signature verification key N_U for his signature and a cipher key K, then enciphers said signature verification key N_U and said cipher key K to generate enciphered user information E_I (X,K,N_U), and sends it to said bank;

step (3) wherein said bank withdraws said amount of money X from the user'"'"'s bank account, and sends information {X,E_I (X,K,N_U)} as an electronic cash issuance request to said electronic cash issuer, while at the same time said bank records in a user data base the user name U and said enciphered user information E_I (X,K,N_U) in correspondence with each other;

step (4) wherein said electronic cash issuer uses a decipher function D_I to decipher said enciphered user information E_I (X,K,N_U) to obtain information (X,K,N_U), generates information n=g(N_U) containing said signature verification key N_U, signs said information n and said amount of money X to create an issuer signature S_I (X,n), then registers said information n and E_I (X,K,N_U) in an inspection data base in correspondence with each other, and calculates an enciphered issuer signature E_K (S_I (X,n)) obtained by enciphering said issuer signature S_I (X,n) by said cipher key K, and sends said enciphered issuer signature E_K (S_I (X,n)) to said user;

step (5) wherein said user deciphers said enciphered issuer signature E_K (S_I (X,n)) by said key K into said issuer signature S_I (X,n);

step (6) wherein said user sends, as electronic cash C of said face value X, information containing {N_U,X,S_I (X,n)} to said shop for the payment thereto in an amount y;

step (7) wherein said shop verifies the validity of said electronic cash C and, if valid, receives the payment in said amount y;

step (8) wherein said shop sends to said electronic cash issuer all communication data H concerning the payment by said electronic cash and requests said issuer to settle accounts with said shop; and

step (9) wherein said electronic cash issuer obtains, with said signature verification key N_U in said communication data H, said information n=g(N_U) containing said key N_U, makes a check to see if said information n is already registered in said inspection data base, verifies the validity of said electronic cash and, if valid, instructs said bank to transfer the amount of payment y to a bank account of said shop.

3. The method of claim 1 or 2, wherein said step (3) is a step wherein said bank attaches a signature S_B (X,E_I) to information (X,E_I) sent from said user and sends it to said issuer together with said information (X,E_I), and said step (4) is a step wherein said issuer verifies the validity of said signature S_B (X,E_I) and, if valid, deciphers said information by said decipher function D_I, compares said deciphered amount of money X and the amount of money X sent from said bank and, if they match, generates said issuer signature S_I.

4. The method of claim 1 or 2, wherein said step (7) comprises:

step (7a) wherein said shop receives from said user said electronic cash C containing a balance x, then generates arbitrary information e and sends it to said user;

step (7b) wherein said user calculates a signature S_U (e,y) of said user for said information e sent from said shop and said amount of payment y and sends said signature S_U (e,y) to said shop together with said amount of payment y; and

step (7c) wherein said shop verifies the validity of said issuer signature S_I (X,n) by a public key PS_I for the verification of said issuer signature and a signature verification function V_I, further verifies the validity of said user signature S_U (e,y) by said user signature verification key N_U contained in said electronic cash C received from said user, while at the same time said shop verifies if said balance x satisfies a condition y≦

x, and, if the results of all the verifications are valid, approves the payment by said electronic cash C of said amount y.

5. The method of claim 4, wherein said step (7) is a step:

wherein said shop verifies the validity of said issuer signature S_I (X,n) contained in said electronic cash C by using said public signature verification key PS_I and, if valid, calculates a one-way function f(TIME,W) using time information TIME and shop information W as variables, then generates said information e and sends it to said user together with said time information TIME and said shop information W as well; and

wherein said user calculates a one-way function e=f (TIME,W) using said time information TIME and said shop information W as variables, then compares said one-way function e with said information e sent from said shop and, if they match, sends said information {y,S_U (e,y)} to said shop.

6. The method of claim 4, wherein said step (9) comprises:

step (9a) wherein said issuer makes a check to see if said information n derived from said communication data received from said shop is already registered in said inspection data base;

step (9b) wherein if said information n is registered, said issuer updates with a value Y+y the total amount of money used Y corresponding to said information n,

step (9c) wherein said issuer makes a check to see if said value Y+y is smaller than said face value X and, if so, instructs said bank to transfer said amount of money y to a bank account of said shop;

step (9d) wherein if Y+y=X, said issuer erases said information n from said inspection data base; and

step (9e) wherein if Y+y>

X, said issuer decides that said user overspent, and sends said information E_I to said bank to specify the mane of overspender from information stored in a user data base of said bank.

7. The method of claim 1 or 2, wherein said information n=g(N_U) is n=N_U.

8. The method of claim 1 or 2, wherein said step (7) includes a step wherein when said electronic cash is verified to be valid by said shop, said user updates the balance x of said electronic cash with a value x-y.

9. The method of claim 1 or 2, wherein said step (4) includes a step wherein said issuer sends said enciphered issuer signature E_K to said user via said bank.

2. An electronic cash implementing method 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 method comprising:

step (1) wherein said electronic cash issuer opens an encipher function E₁ and a signature verification function V₁ to the public;

step (2) wherein said user sends to said bank user information U and a face value x for requesting said bank to withdraw an amount of money X from his bank account and issue electronic cash of said face value X, while at the same time said user generates a cipher key K, then enciphers said amount of money X and said cipher key K to generate enciphered user information E_I (X,K), and sends it to said bank;

step (3) wherein said bank withdraws said amount of money X from the user'"'"'s bank account, and sends information {X,E_I (X,K)} as an electronic cash issuance request to said electronic cash issuer, while at the same time said bank records in a user data base the user name U and said enciphered user information E_I (X,K) in correspondence with each other;

step (4) wherein said electronic cash issuer responds to said electronic cash issuance request to generate a signature verification key N_U for said user and information n=g(N_U) containing said signature verification key N_U, registers said information n and E_I (X,K) in an inspection data base in correspondence with each other, deciphers said received information E_I (X,K) by a decipher function D_I to obtain information (X,K), creates an issuer signature S_I (X,n), then calculates an enciphered issuer signature E_K (N_U,S_I (X,n)) obtained by enciphering said issuer signature S_I (X,n) by said cipher key K, and sends said enciphered issuer signature E_K (N_U,S_I (X,n)) to said user;

step (5) wherein said user deciphers said enciphered issuer signature E_K (N_U,S_I (X,n)) by said key K into said issuer signature S_I (X,n);

step (6) wherein said user sends, as electronic cash C of said face value X, information containing {N_U,X,S_I (X,n)} to said shop for the payment thereto in an amount y;

step (7) wherein said shop verifies the validity of said electronic cash C by said signature verification key N_U and, if valid, receives the payment in said amount y;

step (8) wherein said shop sends to said electronic cash issuer all communication data H concerning the payment by said electronic cash and requests said issuer to settle accounts with said shop; and

step (9) wherein said electronic cash issuer obtains, with said signature verification key N_U in said communication data H, said information n=g(N_U), makes a check to see if said information n is already registered in said inspection data base, verifies the validity of said electronic cash and, if valid, instructs said bank to transfer the amount of payment y to a bank account of said shop.

10. A user 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 user apparatus comprising:

input means for inputting an amount of money X and an amount of payment y;

cipher key generating means for generating a cipher key K;

Key generating means for generating a signature generating key SS_U and a signature verification key N_U ;

encipher means for enciphering said amount of money X and said keys K and N_U by a public cipher function E_I of said electronic cash issuer to obtain the information E_I (X,K,N_U);

means for sending to said bank said enciphered information E_I (X,K,N_U), user information U and a message requesting said bank to withdraw said amount of money X from a bank account of said user;

decipher means for deciphering an enciphered issuer signature from said bank by said key K to obtain a signature S_I (X,N_U) of said issuer;

signature generating means for generating a user signature S_U (e,y) by said user signature generating key SS_U for information e in information received from said shop and said amount of payment y; and

means for sending said amount of money X, said amount of payment y, said signature verification key N_U and said signatures S_I (X,N_U) and S_U (e,y) to said shop.

11. A bank 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 bank apparatus comprising:

means for receiving from said user enciphered information E_I (X,K,N_U), user information U and a request for issuance of electronic cash of a face value X;

a user data base for storing said enciphered information E_I (X,K,N_U) and said user information U in correspondence with each other;

means for attaching a bank signature S_B to said enciphered information E_I (X,K,N_U) and said amount of money X to obtain information S_B (X,E_I (X,K,N_U)) and for sending it to said issuer together with said amount of money X and said enciphered information E_I (X,K,N_U);

means for sending to said user said enciphered issuer signature E_K received from said issuer; and

means for retrieving from said user data base said user information U corresponding to said enciphered user information E_I (X,K,N_U) received together with a retrieval request from said electronic cash issuer.

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_I (X,K,N_U) from the bank by a secret key SE_I of a public key cryptosystem to obtain an amount of money X, user cipher key K and a user signature verification key N_U ;

an inspection database for registering said user signature verification key N_U, said enciphered information E_I (X,K,N_U) and the total amount of money paid so far Y as a set;

signature generating means for generating an issuer signature S_I (X,N_U) for said amount of money X and said user signature verification key N_U ;

encipher means for enciphering said issuer signature S_I (X,N_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_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; and

means 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_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_I (X,K,N_U) corresponding to said verification key N_U and sends said read-out information E_I (X,K,N_U) to said bank so as to trace an abuser or overspender.

13. A shop apparatus for an electronic cash system which is composed of an electronic cash issuer, a bank which managers account information of a user, a user who uses electronic cash for payment, and a shop which receives a payment by electronic cash, said shop apparatus comprising:

means for receiving electronic cash C, the amount of payment y and a user signature S_U (e,y) from said user;

issuer signature verifying means for verifying the validity of an issuer signature S_I (X,N_U) in said electronic cash C received from the user;

user signature verifying means for verifying the validity of said received user signature by using said received user signature verification key N_U ;

means for making a check to see if said received amount of payment y is smaller than the amount of money X in said received electronic cash C;

means for generating information e using shop information W as a variable and for sending said information e to said user; and

means for sending, to said issuer, communication data between said user and said shop concerning the payment by said electronic cash.