Network sales system

Background of the Invention

0001This invention relates to user-interactive network sales systems for implementing an open marketplace for goods or services over computer networks such as the Internet.

0002U.S. Patent Application Serial No. 08/168,519, filed December 16, 1993 by David K. Gifford and entitled "Digital Active Advertising," the entire disclosure of which is hereby incorporated herein in its entirety by reference, describes a network sales system that includes a plurality of buyer computers, a plurality of merchant computers, and a payment computer. A user at a buyer computer asks to have advertisements displayed, and the buyer computer requests advertisements from a merchant computer, which sends the advertisements to the buyer computer. The user then requests purchase of an advertised product, and the buyer computer sends a purchase message to the merchant computer. The merchant computer constructs a payment order that it sends to the payment computer, which authorizes the purchase and sends an authorization message to the merchant computer. When the merchant computer receives the authorization message it sends the product to the buyer computer.

0003The above-mentioned patent application also describes an alternative implementation of the network sales system in which, when the user requests purchase of an advertised product, the buyer computer sends a payment order directly to the payment computer, which sends an authorization message back to the buyer computer that includes an unforgeable certificate that the payment order is valid. The buyer computer then constructs a purchase message that includes the unforgeable certificate and sends it to the merchant computer. When the merchant computer receives the purchase request it sends the product to the buyer computer, based upon the pre-authorized payment order.

Summary of the Invention

0004In one aspect, the invention provides a network-based sales system that includes at least one buyer computer for operation by a user desiring to buy a product, at least one merchant computer, and at least one payment computer. The buyer computer, the merchant computer, and the payment computer are interconnected by a computer network. The buyer computer is programmed to receive a user request for purchasing a product, and to cause a payment message to be sent to the payment computer that comprises a product identifier identifying the product. The payment computer is programmed to receive the payment message, to cause an access message to be created that comprises the product identifier and an access message authenticator based on a cryptographic key, and to cause the access message to be sent to the merchant computer. The merchant computer is programmed to receive the access message, to verify the access message authenticator to ensure that the access message authenticator was created using the cryptographic key, and to cause the product to be sent to the user desiring to buy the product.

0005The invention provides a simple design architecture for the network sales system that allows the merchant computer to respond to payment orders from the buyer computer without the merchant computer having to communicate directly with the payment computer to ensure that the user is authorized to purchase the product and without the merchant computer having to store information in a database regarding which buyers are authorized to purchase which products. Rather, when the merchant computer receives an access message from the buyer computer identifying a product to be purchased, the merchant computer need only check the access message to ensure that it was created by the payment computer (thereby establishing for the merchant computer that the buyer is authorized to purchase the product), and then the merchant computer can cause the product to be sent to the buyer computer who has been authorized to purchase the product.

0006In another aspect, the invention features a network-based sales system that includes at least one buyer computer for operation by a user desiring to buy products, at least one shopping cart computer, and a shopping cart database connected to the shopping cart computer. The buyer computer and the shopping cart computer are interconnected by a computer network. The buyer computer is programmed to receive a plurality of requests from a user to add a plurality of respective products to a shopping cart in the shopping cart database, and, in response to the requests to add the products, to send a plurality of respective shopping cart messages to the shopping cart computer each of which includes a product identifier identifying one of the plurality of products. The shopping cart computer is programmed to receive the plurality of shopping cart messages, to modify the shopping cart in the shopping cart database to reflect the plurality of requests to add the plurality of products to the shopping cart, and to cause a payment message associated with the shopping cart to be created. The buyer computer is programmed to receive a request from the user to purchase the plurality of products added to the shopping cart and to cause the payment message to be activated to initiate a payment transaction for the plurality of products added to the shopping cart.

0007In another aspect, the invention features a network-based link message system that includes at least one client computer for operation by a client user and at least one server computer for operation by a server user. The client computer and the server computer are interconnected by a computer network. The client computer is programmed to send an initial link message to the server computer. The server computer is programmed to receive the initial link message from the client computer and to create, based on information contained in the initial link message, a session link message that encodes a state of interaction between the client computer and the server computer. The session link message includes a session link authenticator, computed by a cryptographic function of the session link contents, for authenticating the session link message. The server computer is programmed to cause the session link message to be sent to the client computer. The client computer is programmed to cause the session link message to be sent to a computer in the network that is programmed to authenticate the session link message by examining the session link authenticator and that is programmed to respond to the session link message based on the state of the interaction between the client computer and the server computer.

0008In another aspect, the invention features a network-based sales system that includes a merchant database having a plurality of digital advertisements and a plurality of respective product fulfillment items, at least one creation computer for creating the merchant database, and at least one merchant computer for causing the digital advertisements to be transmitted to a user and for causing advertised products to be transmitted to the user. The creation computer and the merchant computer are interconnected by a computer network. The creation computer is programmed to create the merchant database, and to transmit the digital advertisements and the product fulfillment items to the merchant computer. The merchant computer is programmed to receive the digital advertisements and product fulfillment items, to receive a request for a digital advertisement from a user, to cause the digital advertisement to be sent to the user, to receive from the user an access message identifying an advertised product, and to cause the product to be sent to the user in accordance with a product fulfillment item corresponding to the product.

0009In another aspect, the invention features a hypertext statement system that includes a client computer for operation by a client user and one or more server computers for operation by a server user. The client computer and the server computers are interconnected by a computer network. At least one of the server computers is programmed to record purchase transaction records in a database. Each of the purchase transaction records includes a product description. The server computer is programmed to transmit a statement document that includes the purchase transaction records to the client computer. The client computer is programmed to display the product descriptions, to receive a request from the client user to display a product corresponding to a product description displayed by the client computer, and to cause a product hypertext link derived from a purchase transaction record to be activated. At least one of the server computers is programmed to respond to activation of the product hypertext link by causing the product to be sent to the client computer.

0010In another aspect, the invention features a network payment system that includes at least one buyer computer for operation by a user desiring to buy a product and at least one payment computer for processing payment messages from the buyer computer. The buyer computer and the payment computer are interconnected by a computer network. The buyer computer is programmed to cause a payment message to be sent to the payment computer. The payment message includes a product identifier identifying the product that the user desires to buy. The payment computer is programmed to receive the payment message, to cause an access message to be created to enable the user to access the product, and to record a purchase transaction record in the settlement database. The buyer computer is programmed to cause a request for purchase transaction records to be sent to the payment computer. The payment computer is programmed to receive the request for purchase transaction records and to cause a document derived from the purchase transaction records to be sent to the buyer computer.

Brief Description of the Drawings

0011Fig. 1 is a block diagram of a network sales system in accordance with the present invention.

0012Fig. 2 (2-A through 2-I) is a flowchart diagram illustrating the operation of a purchase transaction in the network sales system of Fig. 1.

0013Fig. 3 (3-A through 3-B) is a flowchart diagram illustrating the use of a shopping cart for the purchase of products in connection with the network sales system of Fig. 1.

0014Fig. 4 (4-A through 4-C) is a flowchart diagram illustrating the operation of a smart statement in the network sales system of Fig. 1.

0015Fig. 5 is a screen snapshot of an advertising document that the merchant computer sends to the buyer computer in Fig. 2.

0016Fig. 6 is a screen snapshot of a confirmation document that the payment computer sends to the buyer computer in Fig. 2.

0017Fig. 7 is a screen snapshot of a new account document that the payment computer sends to the buyer computer in Fig. 2.

0018Fig. 8 is a screen snapshot of an account name prompt that the buyer computer creates in Fig. 2.

0019Fig. 9 is a screen snapshot of a document that the payment computer sends to the buyer computer in Fig. 2 and that provides an option either to repurchase or to use a previously purchased access.

0020Fig. 10 is a screen snapshot of a fulfillment document that the merchant computer sends to the buyer computer in Fig. 2.

0021Fig. 11 is a screen snapshot of a smart statement document that the payment computer sends to the buyer computer in Fig. 4.

0022Figs. 12 and 13 are screen snapshots of a transaction detail document that the payment computer sends to the buyer computer in Fig. 4.

0023Fig. 14 is a screen snapshot of a customer service form that the payment computer sends to the buyer computer in Fig. 4.

Detailed Description

0024With reference to Fig. 1, a network sales system in accordance with the present invention includes a buyer computer 12 operated by a user desiring to buy a product, a merchant computer 14, which may be operated by a merchant willing to sell products to the buyer or by a manager of the network sales system, a payment computer 16 typically operated by a manager of the network sales system, and a creation computer 20 typically operated by the merchant. The buyer, merchant, payment, and creation computers are all inter-connected by a computer network 10 such as the Internet.

0025Creation computer 20 is programmed to build a "store" of products for the merchant. A printout of a computer program for use in creating such a "store" in accordance with the present invention is provided as Appendix F.

0026The products advertised by merchant computer 14 may be, for example, newspaper or newsletter articles available for purchase by buyers. Creation computer 20 creates a digital advertisement database 18 that stores advertising documents (which may for example be in the form of summaries of newspaper or newsletter articles, accompanied by prices) and product fulfillment items (which may be the products themselves if the products can be transmitted over the network, or which may be hard goods identifiers if the products are hard goods, i.e., durable products as opposed to information products). Creation computer 20 transmits contents of the advertising document database 18 to merchant computer 14 to enable the merchant computer to cause advertisements and products to be sent to buyers. Merchant computer 14 maintains advertising documents locally in advertising document database 15. In an alternative embodiment, the creation computer does not have a local digital advertisement database, but instead updates a remote advertising document database on a merchant computer. These updates can be accomplished using HTML forms or other remote database technologies as is understood by practitioners of the art.

0027Payment computer 16 has access to a settlement database 22 in which payment computer 16 can record details of purchase transactions. The products may be organized into various "domains" of products, and payment computer 16 can access settlement database 22 to record and retrieve records of purchases of products falling within the various domains. Payment computer 16 also has access to a shopping cart database 21 in which a "shopping cart" of products that a user wishes to purchase can be maintained as the user shops prior to actual purchase of the contents of the shopping cart.

0028With reference to Fig. 2, a purchase transaction begins when a user at buyer computer 12 requests advertisements (step 24) and buyer computer 12 accordingly sends an advertising document URL (universal resource locator) to merchant computer 14 (step 26). The merchant computer fetches an advertising document from the advertising document database (step 28) and sends it to the buyer computer (step 30). An example of an advertising document is shown in Fig. 5. Details of URLs and how they are used are found in the microfiche Appendix G.

0029The user browses through the advertising document and eventually requests a product (step 32). This results in the buyer computer sending payment URL A to the payment computer (step 34). Payment URL A includes a product identifier that represents the product the user wishes to buy, a domain identifier that represents a domain of products to which the desired product belongs, a payment amount that represents the price of the product, a merchant computer identifier that represents merchant computer 14, a merchant account identifier that represents the particular merchant account to be credited with the payment amount, a duration time that represents the length of time for which access to the product is to be granted to the user after completion of the purchase transaction, an expiration time that represents a deadline beyond which this particular payment URL cannot be used, a buyer network address, and a payment URL authenticator that is a digital signature based on a cryptographic key. The payment URL authenticator is a hash of other information in the payment URL, the hash being defined by a key shared by the merchant and the operator of the payment computer.

0030In an alternative embodiment, step 34 consists of the buyer computer sending a purchase product message to the merchant computer, and the merchant computer provides payment URL A to the buyer computer in response to the purchase product message. In this alternative embodiment, payment URL A contains the same contents as above. The buyer computer then sends the payment URL A it has received from the merchant computer to the payment computer.

0031When the payment computer receives the payment URL it verifies whether the payment URL authenticator was created from the contents of the payment URL using the cryptographic key (step 36). If not, the payment computer sends a document to the buyer computer indicating that access to the network sales system is denied (step 38). Otherwise, the payment computer determines whether the expiration time has past (step 40). If it has, the payment computer sends a document to the buyer computer indicating that the time has expired (step 41). Otherwise, the payment computer checks the buyer computer network address to see if it matches the one specified in the payment URL (step 42). If it does not match, the payment computer sends a document to the buyer computer indicating that access to the network payment system is denied (step 43). Otherwise, the payment computer sends a payment confirmation document to the buyer computer, the payment confirmation document including an "open" link and a "continue" link (step 44).

0032An example of a confirmation document is shown in Fig. 6. The confirmation document asks the user to click on a "continue" button if the user already has an account with the payment computer, or to click on an "open" button if the user does not already have an account and wishes to open one.

0033If the user clicks on the "open" button (step 46), the buyer computer sends payment URL C to the payment computer (step 48), payment URL C being similar to payment URL A but also indicating that the user does not yet have an account. The payment computer creates a new account document (step 50) and sends it to the buyer computer (step 52). An example of a new account document is shown in Fig. 7. When the user receives the new account document he enters the new account name, an account password, a credit card number, the credit card expiration date, and security information such as the maiden name of the user's mother (step 54), and presses a "submit" button (not shown in Fig. 7). The buyer computer sends the new account information to the payment computer (step 56), which enters the new account in the settlement database (step 58).

0034If the user clicks on the "continue" button (step 60), the buyer computer sends payment URL B to the payment computer (step 62), payment URL B being similar to payment URL A but also indicating that the user already has an account. The payment computer then instructs the buyer computer to provide the account name and password (steps 64 and 66), and the buyer computer prompts the user for this information by creating an account name prompt (example shown in Fig. 8) and a similar password prompt. The user enters the information (step 68) and the buyer computer sends the account name and password to the payment computer (step 70).

0035The payment computer verifies whether the user name and password are correct (step 72). If they are not correct, the payment computer sends a document to the buyer computer indicating that access to the network sales system is denied (step 74). Otherwise, the payment computer determines whether additional security is warranted, based on, e.g., whether the payment amount exceeds a threshold (step 73). If additional security is warranted, the payment computer creates a challenge form document and sends it to the buyer computer (step 75). The user enters the security information (step 77), the buyer computer sends the security information to the payment computer (step 79), and the payment computer determines whether the security information is correct (step 81). If it is not correct, the payment computer sends a document to the buyer computer indicating that access to the network sales system is denied (step 83).

0036If the security information is correct, or if additional security was not warranted, the payment computer checks the settlement database to determine whether the user has unexpired access to the domain identifier contained in the payment URL (step 82). If so, the payment computer sends to the buyer computer a document providing an option either to repurchase or to use the previously purchased access (step 84). An example of such a document is shown in Fig. 9. The user can respond to the recent purchase query document by choosing to access the previously purchased document (step 85) or to go ahead and buy the currently selected product (step 86).

0037If the user chooses to access the previously purchased document, the buyer computer skips to step 92 (see below). If the user chooses to buy the currently selected product, the payment computer calculates an actual payment amount that may differ from the payment amount contained in the payment URL (step 87). For example, the purchase of a product in a certain domain may entitle the user to access other products in the domain for free or for a reduced price for a given period of time.

0038The payment computer then verifies whether the user account has sufficient funds or credit (step 76). If not, the payment computer sends a document to the buyer computer indicating that the user account has insufficient funds (step 78). Otherwise, the payment computer creates an access URL (step 80) that includes a merchant computer identifier, a domain identifier, a product identifier, an indication of the end of the duration time for which access to the product is to be granted, the buyer network address, and an access URL authenticator that is a digital signature based on a cryptographic key. The access URL authenticator is a hash of other information in the access URL, the hash being defined by a key shared by the merchant and the operator of the payment computer. The payment computer then records the product identifier, the domain, the user account, the merchant account, the end of duration time, and the actual payment amount in the settlement database (step 88).

0039The payment computer then sends a redirect to access URL to the buyer computer (step 90), which sends the access URL to the merchant computer (step 92). The merchant computer verifies whether the access URL authenticator was created from the contents of the access URL using the cryptographic key (step 94). If not, the merchant computer sends a document to the buyer computer indicating that access to the product is denied (step 96).

0040Otherwise, the merchant computer verifies whether the duration time for access to the product has expired (step 98). This is done because the buyer computer can request access to a purchased product repeatedly. If the duration time has expired, the merchant computer sends a document to the buyer computer indicating that the time has expired (step 100). Otherwise the merchant computer verifies that the buyer computer network address is the same as the buyer network address in the access URL (step 101), and if so, sends a fulfillment document to the buyer computer (step 102), which is displayed by the buyer computer (step 104). An example of a fulfillment document is shown in Fig. 10. Otherwise, the merchant computer sends a document to the buyer computer indicating that access is not allowed (step 103).

0041With reference now to Fig. 3, when the merchant computer sends the advertising document to the buyer computer, the user may request that a product be added to a shopping cart in the shopping cart database rather than request that the product be purchased immediately. The buyer computer sends a shopping cart URL to the payment computer (step 108), the shopping cart URL including a product identifier, a domain identifier, a payment amount, a merchant computer identifier, a merchant account identifier, a duration time, an expiration time, and a shopping cart URL authenticator that is a digital signature based on a cryptographic key. The shopping cart URL authenticator is a hash of other information in the shopping cart URL, the hash being defined by a key shared by the merchant and the operator of the payment computer.

0042The payment computer verifies whether the shopping cart URL authenticator was created from the contents of the shopping cart URL using a cryptographic key (step 110). If not, the payment computer sends a document to the buyer computer indicating that access to the network sales system is denied (step 112). Otherwise, before any modification to a user's shopping cart is allowed, user authentication is performed (step 113) in a manner analogous to steps 40-81. Once the user is authenticated, the payment computer creates or updates a payment URL for the shopping cart (step 114).

0043The user then either requests more advertisements (step 24 in Fig. 2) and possibly adds another product to the shopping cart, requests display of the shopping cart (step 116), or requests purchase of the entire contents of the shopping cart (step 124). If the user requests display of the shopping cart (step 116), the buyer computer sends a fetch shopping cart request to the payment computer (step 118), and the payment computer and buyer computer (step 119) perform steps analogous to steps 64-81. The payment computer returns the contents of the shopping cart to the buyer computer (step 120), which displays the contents of the shopping cart (step 122). If the user requests that the entire contents of the shopping cart be purchased (step 124) the buyer computer causes the payment URL for the shopping cart to be activated (step 126) and the payment URL is processed in a manner analogous to the processing of payment URLs for individual products (beginning with step 36 in Fig. 2).

0044With reference now to Fig. 4, a user can request display of a "smart statement" that lists purchase transactions for a given month (step 128). When the buyer computer receives such a request, it sends a smart statement URL to the payment computer (step 130).

0045When the payment computer receives the smart statement URL, it verifies whether the smart statement URL authenticator was created from the contents of the smart statement URL using a cryptographic key (step 132). If not, the payment computer sends a document to the buyer computer indicating that access is denied (step 134). Otherwise, the payment computer checks to determine whether the buyer network address in the smart statement URL matches the buyer computer's actual network address (step 136). If not, the payment computer sends a document to the buyer computer indicating that access is denied (step 138). Otherwise (step 140), the payment computer and buyer computer perform a set of steps analogous to steps 64-81 in Fig. 2 (payment computer requests account name and password, user provides the requested information, and payment computer verifies the information).

0046In an alternative embodiment steps 132-138 are omitted.

0047After verification of account information is complete, the payment computer retrieves the requested settlement data from the settlement database, creates a smart statement document for the buyer, and sends the smart statement document to the buyer computer (step 142). An example of a smart statement document is shown in Fig. 11. Each purchase transaction record in the smart statement document includes the data of the transaction, the name of the merchant, an identification of the product, and the payment amount for the product. The smart statement document also includes a transaction detail URL for each purchase transaction (these URLs, or hypertext links, are discussed below and are not shown in Fig. 11). The smart statement document also identifies previous statements that the user may wish to have displayed.

0048The buyer computer displays the retrieved document (step 144), and the user may request transaction details for a particular transaction listed on the smart statement (step 146). If so, the buyer computer sends a transaction detail URL (or "payment detail URL") to the payment computer (step 148). The transaction detail URL includes a transaction identifier, a buyer network address, and a transaction detail URL authenticator. When the payment computer receives the transaction detail URL, it performs (step 150) a set of steps analogous to steps 132-140 (verification of URL authenticator, buyer network address, and account information). The payment computer then retrieves from the settlement database data corresponding to the payment transaction specified in the transaction detail URL, creates a transaction detail document, and sends it to the buyer computer (step 152).

0049An example of a transaction detail document is shown in Figs. 12 and 13. The document displays a number of items of information about the transaction, including the transaction date, end of the duration time ("expiration"), a description of the product, the payment amount, the domain corresponding to the product, an identification of the merchant, and the merchant's address.

0050The smart statement document and the transaction detail document both include customer service URLs (hypertext links) that allow the user to request customer service (i.e., to send comments and suggestions to the payment computer). When the user requests customer service (step 154), the buyer computer sends the customer service URL to the payment computer (step 156), which creates a customer service form and sends it to the buyer computer (step 158). An example of a customer service form is shown in Fig. 14. The user types comments into the customer service form (step 160), and the buyer computer sends the user's comments to the payment computer (step 162). The payment computer then posts the user comments and sends a thank you document to the buyer computer (step 164).

0051A user may request display of a product included in the smart statement. When the user requests that the product be displayed (step 166), the buyer computer sends the access URL contained in the smart statement document to the merchant computer (step 168), and the buyer computer and merchant computer perform a set of steps analogous to steps 94-104 in Fig. 2 (authentication of access URL, verification whether duration time has expired, verification of buyer network address, and transmission of fulfillment document to buyer computer).

0052Whenever the present application states that one computer sends a URL to another computer, it should be understood that in preferred embodiments the URL is sent in a standard HTTP request message, unless a URL message is specified as a redirection in the present application. The request message includes components of the URL as described by the standard HTTP protocol definition. These URL components in the request message allow the server to provide a response appropriate to the URL. The term "URL" as used the present application is an example of a "link," which is a pointer to another document or form (including multimedia documents, hypertext documents including other links, or audio/video documents).

0053When the present application states that one computer sends a document to another computer, it should be understood that in preferred embodiments the document is a success HTTP response message with the document in the body of the message. When the present application states that a server sends an account name and password request message to the client, it should be understood that in preferred embodiments the account name and password request message is an unauthorized HTTP response. A client computer sends account name and password information to a server as part of a request message with an authorization field.

0054The software architecture underlying the particular preferred embodiment is based upon the hypertext conventions of the World Wide Web. For example, the Hypertext Markup Language (HTML) document format is used to represent digital advertisements. The HTML forms fill out support is used in Mosaic 2.0. The Hypertext Transfer Protocol (HTTP) is used between buyer and merchant computers. Documents are named with Uniform Resource Locators (URLs) in the network of computers. URLs are authenticated using digital signatures.

0055There has been described a new and useful network based sales system. It is apparent that those skilled in the art may make numerous modifications and departures from the specific embodiments described herein without departing from the spirit and scope of the claimed invention.

0056As has been described, a network-based sales system, comprises: at least one buyer computer for operation by a user desiring to buy a product; at least one merchant computer; and at least one payment computer; the buyer computer, the merchant computer, and the payment computer being interconnected by a computer network; the buyer computer being programmed to receive a user request for purchasing a product, and to cause a payment message to be sent to the payment computer that comprises a product identifier identifying the product; the payment computer being programmed to receive the payment message, to cause an access message to be created that comprises the product identifier and an access message authenticator based on a cryptographic key, and to cause the access message to be sent to the merchant computer; and the merchant computer being programmed to receive the access message, to verify the access message authenticator to ensure that the access message authenticator was created using the cryptographic key, and to cause the product to be sent to the user desiring to buy the product.

0057The payment message and the access message may each comprise a universal resource locator. The payment computer can be programmed to identify the merchant computer upon receipt of the payment message from the buyer computer. The access message may comprise a buyer network address. In this case, the product can be transmitted from one computer to another; and the merchant computer can cause the product to be sent to the user by transmitting the product to the buyer network address only. The merchant computer is preferably programmed to verify whether the buyer network address in the access message matches the actual network address of the buyer computer. The payment message may comprise a buyer network address. The payment computer may be programmed to verify whether the buyer network address in the payment message matches the actual network address of the buyer computer.

0058The access message authenticator may comprise a cryptographic function of contents of the access message based on the cryptographic key. The payment computer may be programmed to verify the payment message authenticator to ensure that the payment message authenticator was created using the cryptographic key. The payment message authenticator can comprise a cryptographic function of contents of the payment message based on the cryptographic key. The payment message may comprise a payment amount. The payment message can comprise a merchant account identifier that identifies a merchant account. The buyer computer may be programmed to transmit a user account identifier to the payment computer that identifies a user account. The payment message can comprise a payment amount; and the payment computer may be programmed to ensure that the user account has sufficient funds or credit to cover the payment amount. The payment message may comprise a payment amount and a merchant account identifier that identifies a merchant account; and the payment computer may be programmed to record the payment amount, the user account, and the merchant account in a settlement database.

0059The payment message can comprise a domain identifier; and the payment computer may be programmed to record the domain identifier and the user account in a settlement database. The payment computer may be programmed to check the settlement database, upon receipt of the payment message, to determine whether the user account has previously purchased a product associated with the domain identifier. The payment computer may be programmed to determine an actual payment amount for the product identified by the product identifier in the payment message based on whether the user account has previously purchased a product associated with the domain identifier. The buyer computer may be programmed to transmit a user authenticator to the payment computer and the payment computer is programmed to verify the user authenticator. The user authenticator comprises a password. The buyer computer may be programmed to transmit security information to the payment computer; the payment computer may be programmed to transmit a challenge form to the buyer computer under a predetermined condition, the challenge form asking for the security information previously transmitted by the buyer computer to the payment computer; the payment computer may be programmed to respond to the challenge form by querying the user for the security information and transmitting the security information to the payment computer; and the payment computer may be programmed to verify authenticity of the security information. The payment message may comprise a payment amount; and the predetermined condition may comprise receipt of a payment amount in the payment message that exceeds a threshold.

0060The payment message may comprise a merchant computer identifier that identifies the merchant computer. The access message may comprise the merchant computer identifier. The payment message may comprise a duration time that specifies a length of time for which access to the product is to be granted. The payment computer may be programmed to use the duration time to compute an end of duration time and to cause the end of duration time to be included in the access message. The merchant computer may be programmed to verify, upon receipt of the access message, that the end of duration time has not past. The payment message may comprise an expiration time after which the payment message can no longer be used. The payment computer may be programmed to verify, upon receipt of the payment message, that the expiration time has not past. The payment computer may be programmed to cause the access message to be sent to the buyer computer; and the buyer computer may be programmed to cause the access message received from the payment computer to be sent to the merchant computer.

0061A network-based sales system, comprises: at least one buyer computer for operation by a user desiring to buy a product; at least one merchant computer; and at least one payment computer; the buyer computer, the merchant computer, and the payment computer being interconnected by a computer network; the buyer computer being programmed to receive a user request for purchasing a product, and to cause a payment URL to be sent to the payment computer that comprises a product identifier identifying the product, a payment amount, and a payment URL authenticator comprising a cryptographic key; the payment computer being programmed to receive the payment URL, to verify the payment URL authenticator to ensure that the payment URL authenticator was created using the cryptographic key, to ensure that the user has sufficient funds or credit to cover the payment amount, to identify the merchant computer operated by the merchant willing to sell the product t the buyer, to cause an access URL to be created that comprises the product identifier and an access URL authenticator comprising a cryptographic function of contents of the access URL based on a cryptographic key, and to cause the access URL to be sent to the buyer computer; the buyer computer being programmed to cause the access URL received from the payment computer to be sent to the merchant computer; and the merchant computer being programmed to receive the access URL, to verify the access URL authenticator to ensure that the access URL authenticator was created using the cryptographic key, and to cause the product to be sent to the user desiring to but the product.

0062As also described, in a method of operating a payment computer in a computer network comprising at least one buyer computer for operation by a user desiring to buy a product, at least one merchant computer, and at least one payment computer, the method comprises the steps of: receiving, at the payment computer, a payment message that the buyer computer has caused to be sent to the payment computer in response to a user request for purchasing a product, the payment message comprising a product identifier identifying the product; causing an access message to be created that comprises the product identifier and an access message authenticator based on a cryptographic key; and causing the access message to be sent to the merchant computer, the merchant computer being programmed to receive the access message, to verify the access message authenticator to ensure that the access message authenticator was created using the cryptographic key, and to cause the product to be sent to the user desiring to buy the product.

0063As also described, a network-based sales system, comprises: at least one buyer computer for operation by a user desiring to buy products; at least one shopping cart computer; and a shopping cart database connected to the shopping cart computer; the buyer computer and the shopping cart computer being interconnected by a computer network; the buyer computer being programmed to receive a plurality of requests from a user to add a plurality of respective products to a shopping cart in the shopping cart database, and, in response to the requests to add the products, to send a plurality of respective shopping cart messages to the shopping cart computer each of which comprises a product identifier identifying one of the plurality of products; the shopping cart computer being programmed to receive the plurality of shopping cart messages, to modify the shopping cart in the shopping cart database to reflect the plurality of requests to add the plurality of products to the shopping cart, and to cause a payment message associated with the shopping cart to be created; and the buyer computer being programmed to receive a request from the user to purchase the plurality of products added to the shopping cart and to cause the payment message to be activated to initiate a payment transaction for the plurality of products added to the shopping cart. The shopping cart computer may be programmed to cause the payment message to be created before the buyer computer causes the payment message to be activated. The buyer computer may be programmed to receive a request from the user to display the plurality of products added to the shopping cart. The buyer computer may be programmed to transmit a fetch shopping cart request to the payment computer in response to receipt of the request from the user. The payment computer may be programmed to respond to the fetch shopping cart request by transmitting a message to the buyer computer indicating the plurality of products added to the shopping cart; and the buyer computer is programmed to display the plurality of products added to the shopping cart.

0064In a described method of operating a shopping cart computer in a computer network comprising at least one buyer computer for operation by a user desiring to buy products, at least one shopping cart computer, and a shopping cart database connected to the shopping cart computer, the method comprises the steps of: receiving, at the shopping cart computer, a plurality of shopping cart messages sent to the shopping cart computer by the buyer computer in response to receipt of a plurality of requests from a user to add a plurality of respective products to a shopping cart in the shopping cart database, each of the shopping cart messages comprising a product identifier identifying one of the plurality of products; modifying the shopping cart in the shopping cart database to reflect the plurality of requests to add the plurality of products to the shopping cart; and causing a payment message associated with the shopping cart to be created; the buyer computer being programmed to receive a request from the user to purchase the plurality of products added to the shopping cart and to cause the payment message to be activated to initiate a payment transaction for the plurality of products added to the shopping cart.

0065A described network-based link message system, comprises: at least one client computer for operation by a client user; and at least one server computer for operation by a server user; the client computer and the server computer being interconnected by a computer network; the client computer being programmed to send an initial link message to the server computer; the server computer being programmed to receive the initial link message from the client computer, to create, based on information contained in the initial link message, a session link message that encodes a state of interaction between the client computer and the server computer, the session link message comprising a session link authenticator, computed by a cryptographic function of the session link contents, for authenticating the session link message, and to cause the session link message to be sent to the client computer; the client computer being programmed to cause the session link message to be sent to a computer in the network that is programmed to authenticate the session link message by examining the session link authenticator and that is programmed to respond to the session link message based on the state of the interaction between the client computer and the server computer. The client computer may comprise a buyer computer for operation by a user desiring to buy a product; the server computer comprises a payment computer for operation by a manager of the network-based link message system; and the network-based link message system further comprises a merchant computer for operation by a merchant willing to sell the product to the buyer. The computer that is programmed to authenticate the session link message may comprise the merchant computer. The initial link message may comprise a payment message to the payment computer that comprises a product identifier identifying the product. The session link message may comprise an access message that comprises the product identifier identifying the product. The merchant computer is programmed to respond to the access message by causing the product to be sent to the user desiring to buy the product. The initial link message and the session link message may comprise universal resource locators. The session link authenticator may comprise a cryptographic function of contents of the session link message based on a cryptographic key; and the computer to which the client computer is programmed to cause the session link message to be sent is programmed to verify that the session link authenticator was created using the cryptographic key.

0066In a method of operating a server computer in a network-based link message system comprising at least one client computer for operation by a client user and at least one server computer for operation by a server user, the client computer and the server computer being interconnected by a computer network, the method may comprise the steps of: receiving, at the server computer, an initial link message sent to the server computer by the client computer; creating, based on information contained in the initial link message, a session link message that encodes a state of interaction between the client computer and the server computer, the session link message comprising a session link authenticator, computed by a cryptographic function of the session link contents, for authenticating the session link message; and causing the session link message to be sent to the client computer; the client computer being programmed to cause the session link message to be sent to a computer in the network that is programmed to authenticate the session link message by examining the session link authenticator and that is programmed to respond to the session link message based on the state of the interaction between the client computer and the server computer.

0067As also described, a network-based sales system, may comprise: a merchant database comprising a plurality of digital advertisements and a plurality of respective product fulfillment items; at least one creation computer for creating the merchant database; and at least one merchant computer for causing the digital advertisements to be transmitted to the user; the creation computer and the merchant computer being interconnected by a computer network; the creation computer being programmed to create the merchant database, and to transmit the digital advertisements and the product fulfillment items to the merchant computer; the merchant computer being programmed to receive the digital advertisements and product fulfillment items, to receive a request for a digital advertisement from a user, to cause the digital advertisement to be sent to the user, to receive from the user an access sent to the user, to receive from the user an access message identifying an advertised product, and to cause the product to be sent to the user in accordance with a product fulfillment item corresponding to the product. Each of the digital advertisements comprises an abstract of a product and a price. At least one of the product fulfillment items can comprise a product itself; and the creation computer can be programmed to transmit the product to the merchant computer with the digital advertisements. At least one of the product fulfillment items may comprise a hard good identifier to the merchant computer with the digital advertisements.

0068In a method of operating a merchant computer in a network-based sales system comprising a merchant database that comprises a plurality of digital advertisements and a plurality of respective product fulfillment items, at least one creation computer for creating the merchant database, and at least one merchant computer for causing the digital advertisements to be transmitted to a user and for causing advertised products to be transmitted to the user, the creation computer and the merchant computer being interconnected by a computer network, the method comprises the steps of: receiving, at the merchant computer, the digital advertisements and the product fulfillment items having been transmitted to the merchant computer by the creation computer, the merchant database comprising the digital advertisements and the product fulfillment items having been created by the creation computer; receiving a request for a digital advertisement from a user; causing the digital advertisement to be sent to the user; receiving from the user an access message identifying an advertised product; and causing the product to be sent to the user in accordance with a product fulfillment item corresponding to the product.

0069A hypertext statement system is described, comprising: a client computer for operation by a client user; and one or more server computers for operation by a server user; the client computer and the server computers being interconnected by a computer network; at least one of the server computers being programmed to record purchase transaction records in a database, each of the purchase transaction records comprising a product description, and to transmit a statement document comprising the purchase transaction records to the client computer; the client computer being programmed to display the product descriptions, to receive a request from the client user to display a product corresponding to a product description displayed by the client computer, and to cause a product hypertext link derived from a purchase transaction record to be activated; at least one of the server computers being programmed to respond to activation of the product hypertext link by causing the product to be sent to the client computer. The client computer may be programmed to receive a request from the client user to display transaction details corresponding to a product description displayed by the client computer and to cause a transaction detail hypertext link corresponding to the product description to be activated; and the server computer is programmed to respond to activation of the transaction detail hypertext link by transmitting the transaction details to the client computer as a transaction detail document. The transaction detail document may further comprise a customer service form hypertext link; the client computer is programmed to receive a request from the client user to display a customer service form and to cause the customer service form hypertext link to be activated; and the server computer is programmed to respond to activation of the customer service form hypertext link by transmitting the customer service form to the client computer. The statement document may further comprise a customer service form hypertext link; the client computer may be programmed to receive a request from the client user to display a customer service form and to cause the customer service form hypertext link to be activated; and the server computer may be programmed to respond to activation of the customer service form hypertext link by transmitting the customer service form to the client computer.

0070In a method of operating a server computer in a hypertext statement system comprising a client computer for operation by a client user, and one or more server computers for operation by a server user, the client computer and the server computers being interconnected by a computer network, the method comprises the steps of: recording, at one of the server computers, purchase transaction records in a database, each of the purchase transaction records comprising a product description; and transmitting a statement document comprising the purchase transaction records to the client computer; the client computer being programmed to display the product descriptions, to receive a request from the client user to display a product corresponding to a product description displayed by the client computer, and to cause a product hypertext link derived from a purchase transaction record to be activated; at least one of the server computers being programmed to respond to activation of the product hypertext link by causing the product to be sent to the client computer.

0071As has also been described, a network payment system, comprises: at least one buyer computer for operation by a user desiring to buy a product; and at least one payment computer for processing payment messages from the buyer computer; the buyer computer and the payment computer being interconnected by a computer network; the buyer computer being programmed to cause a payment message to be sent to the payment computer, the payment message comprising a product identifier identifying the product that the user desires to buy; the payment computer being programmed to receive the payment message, to cause an access message to be created to enable the user to access the product, and to record a purchase transaction record in the settlement database; the buyer computer being programmed to cause a request for purchase transaction records to be sent to the payment computer; and the payment computer being programmed to receive the request for purchase transaction records and to cause a document derived from the purchase transaction records to be sent to the buyer computer.

0072In a method of operating a payment computer in a network payment system comprising at least one buyer computer for operation by a user desiring to buy a product, and at least one payment computer for processing payment messages from the buyer computer, the method comprises the steps of: receiving, at the payment computer, a payment message that the buyer computer has caused to be sent to the payment computer, the payment message comprising a product identifier identifying the product that the user desires to buy; causing an access message to be created to enable the user to access the product; recording a purchase transaction record in the settlement database; receiving a request for purchase transaction records that the buyer computer has caused to be sent to the payment computer; and causing a document derived from the purchase transaction records to be sent to the buyer computer.