P/00/01 I Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Systems and methods for conducting secure payment transactions using a formatted data structure The following statement is a full description of this invention, including the best method of performing it known to us: SYSTEMS AND METHODS FOR CONDUCTING SECURE PAYMENT TRANSACTIONS USING A FORMATTED DATA STRUCTURE 5 10 BACKGROUND OF INVENTION The present invention relates to the authentication of transactions 15 conducted by parties over open electronic networks such as the Internet. In particular, the invention relates to authentication of Internet transactions in which customers charge payments to payment cards, including credit cards. E-commerce is now popular. Conducting transactions over electronic networks such as the Internet has the now oft-stated advantages of convenience, lower 20 costs, market reach and choice, for both merchants and customers. However, the anonymity of the Internet brings to a commercial or retail sale the issues of fraud and misuse. A transacting merchant has a desire to authenticate the sale, certify the sale, confirm the sale, ensure non-repudiation of the sale, ensure payment, and control anonymity. Similarly, a buyer has a desire to control authentication of the sale, la integrity of the sale, recourse of a bad sale, confirmation of the sale, privacy, and anonymity. Commonly assigned U.S. patent application No. 10/096,271 filed March 11, 2002, which is hereby incorporated by reference in its entirety herein, 5 describes a system and method for conducting secure payment transactions utilizing user software at a customer terminal to receive a set of Web page data to be used for displaying a Web page, which may include one or more hidden fields. The Web page with transaction and cardholder data is sent to the merchant as the purchase data. The merchant may submit this web page data electronically, for example, to an issuer, for 10 authentication or authorization of the payment transaction. Card issuers and other financial institutions now offer or use standardized Internet transaction protocols to improve on- line transaction performance and to accelerate the growth of electronic commerce. Under some standardized protocols (e.g., 3-D SecureTM Protocol developed by Visa International) 15 card issuers or issuing banks may authenticate transactions thereby reducing the likelihood of fraud and associated chargebacks attributed to cardholder not-authorized transactions. The presence of an authenticated transaction may result in an issuer assuming liability for fraud should it occur despite efforts to authenticate the cardholder during an online purchase. Card issuers or issuing banks may assure 20 merchants that they will be paid for issuer-authenticated transactions. The 3-D SecureTM protocol is consistent with and underlies the authentication programs offered by card issuers (e.g., Verified by Visa or MasterCard SecureCodeThl) to authenticate customers for merchants during remote transactions such as those associated with the Internet. The 3-D SecureTM Protocol leverages existing Secure 25 Sockets layer (SSL) encryption functionality and provides enhanced security through issuer authentication of the cardholder during the online shopping session. A piece of software called the Merchant Plug In (MPI) is used by participating merchants to exchange messages, pass information and query participants in order to establish an authentication session between the cardholder and their card issuer during an online 30 purchase.
The 3-D Secure Protocol services are based on a three-domain model the issuer domain, the acquirer and the interoperability domain. The issuer is responsible for managing the enrollment of cardholders in the service, and for authenticating cardholders during on-line transactions. The acquirer is responsible for 5 defining procedures so that merchants participating in Internet transactions operate under an agreement with the acquirer, and for providing back end processing for authenticated transactions. The interoperability domain facilitates the transaction exchange between the other two domains with a common protocol and shared services. Cardholders and their banks may come under "issuer domain", merchants 10 and their banks may come under the "acquirer domain". Communication between issuing and acquiring banks or financial institutions and card issuer infrastructure may come under "Interoperability Domain". While transacting with 3-D Secure compliant banks and merchants, a consumer may have the same Internet shopping experience as previously, except that there is a separate authentication window or pop-up screen 15 from the cardholder's bank to determine if the transacting party is indeed the cardholder of record. The transaction flow for an on-line Internet purchase transaction under the protocol may be as follows: (1) Customers fill in payment data at Merchant web sites in the usual fashion, via an encrypted Secure Sockets Layer (SSL) connection. 20 (2) The Merchant then sends a message through an MYIPI to a Directory, which in turn queries the card issuer, to find out whether the customer is enrolled in the 3-D Secure program. (3) The card issuer responds to the Directory with a message indicating whether the cardholder is enrolled and, if so, provides a Web address for 25 the bank that issued the card. This message is then processed and a response forwarded to the Merchant. (4) The Merchant then sends a message to the issuing bank, through the cardholder device, to initiate and authentication session between the cardholder and the card issuer in which transaction details such as Merchant name and 30 transaction amount may also be presented to the cardholder for confirmation. -3- (5) The issuing bank will then populate an authentication window to the cardholder detailing information related to the transaction such as merchant name and amount, a personal security message, and a response area where authentication details can be entered by the cardholder. 5 (6) The customer approves the transaction in one of a variety of ways, depending on how the issuing bank chooses to implement the system. Options may range from entering a static password or PIN to utilizing a smart card and a Personal Card Reader (PCR) to generate an authentication token. (7) The issuer may process the transaction and cardholder data for 10 authentication. If the authentication is valid, the issuer sends a message to the merchant indicating the authentication was successful. The issuer also notifies the merchant if the authentication failed or was unable to be completed. The message may include an Accountholder Authorization Value (AAV) encoding the authentication process results. Consideration is now being given to ways of enhancing the systems and 15 methods for authenticating customers, who use credit or debit cards for payment in electronic transactions. Attention is directed to the data and the algorithms that are used to securely authenticate the customer or card for payment to the merchant. The solutions should preferably be compatible with industry implementations of common protocols like 3-D Secure and other industry standards such as the EMV standard for smart cards. 20 It is not admitted that any of the information in this specification is common general knowledge, or that the person skilled in the art could be reasonably expected to have ascertained, understood, regarded it as relevant or combined it in anyway at the priority date. SUMMARY OF THE INVENTION The present invention provides a data structure for conveying cardholder 25 transaction authentication information amongst stakeholders in a 3-D Secure environment. In one application environment employing the data structure, authentication programs that are consistent with 3-D Secure protocols are provided for authenticating on-line cardholder transactions. The authentication programs use an access control server (ACS) to authenticate cardholder transactions. Secure Payment Algorithms (SPA) are applied by the 30 ACS to cardholder and transaction information to generate an encrypted Accountholder Authentication Value (AAV), which is assigned to an authenticated transaction. The generated AAV has a data structure in accordance with the invention. 4 The data structure of the invention comprises 20 bytes of Base 64 encoded characters. The first byte is a control byte, bytes 2-9 represent a hash of a merchant name, and byte 10 identifies the particular ACS that authenticates the cardholder transaction. Various authentication methods (e.g., password based, chip based, or PC identification methods) may 5 be used by the ACS to authenticate the cardholder transaction. Byte 11 of the AAV data structure identifies the authentication method and the secret encryption keys that are used by the ACS to generate a Merchant Authentication Code (MAC). Bytes 12-15 of the AAV data structure represent a transaction sequence number identifying a transaction number processed by the ACS, and bytes 16-20 represent the MAC, wherein the MAC comprises portions of 10 an encryption of a concatenation of the card holder's account number, card expiration date and service code, and wherein a pair of keys A and B that are identified in byte 11 is used for encryption. SPA may include suitable encryption processes to generate MAC values for a particular transaction. One encryption process uses a secret key to encrypt a concatenation of 15 the card holder's account number and fields 1-6 (or bytes 1-15) of the AAV. The first 40 bits (or 5 binary bytes) of the encryption result are assigned to the MAC field. In another encryption process, a pair of Data Encryption Standard (DES) keys is used to encrypt a concatenation of the card holder's account number, card expiration date and service code to generate a three-digit Cardholder Verification Code (CVC2) number. This three digit number is converted into 20 binary coded decimal which then is used to populate one and one half bytes of the MAC field in the AAV data structure. The remaining three and one half bytes of the MAC field may be padded or populated with binary zeros. 3-D Secure Protocol electronic messages, which include AAV data, may be digitally signed by the Access control server (ACS). The merchant receiving a message containing the 25 AAV data may be required to validate the digital signature in conformity with the 3-D Secure Protocol before extracting or using the AAV data. Merchants may transfer the AAV data and in particular MAC data to payment authorization request messages. Further features of the invention, its nature, and various advantages will be more apparent from the following detailed description of embodiments with reference to the 30 accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic illustration of an exemplary authentication program utilizing Secure Payment Algorithms (SPA) to generate Accountholder Authentication Values (AAV) for payment transactions, in accordance with the principles of the present invention. 5 FIG. 2 is a schematic illustration of the structure of a Universal Cardholder Account Field, which is used for transporting the output of the Secure Payment Algorithms (SPA) of FIG. 1, in accordance with the principles of the present invention. FIG. 3 is an illustration of some of the steps and message links between entities 5 that are involved in an exemplary payment transaction authentication process, in accordance with the principles of the present invention. FIG. 4 is a schematic illustration of interaction between exemplary authentication and authorization entities involved in the authentication and authorization of on line payment transactions. 10 Throughout the figures, unless otherwise stated, the same reference numerals and characters are used to denote like features, elements, components, or portions of the illustrated embodiments. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION The present invention provides solutions for authenticating remote parties in an 15 electronic transaction, in particular, the solutions relate to Secure Payment Applications (e.g., FIG. I SPA 135) that are used to authenticate a cardholder who remotely participates in the electronic transaction. The solutions may be used for transaction authentication on industry standard e-commerce platforms, such as 3-D Secure compliant e-commerce platforms, and in non e-commerce environments such as mail order and telephone order or mobile devices where 20 an authentication token or code can be used by the issuer to authenticate the cardholder. TABLE I is a glossary of several of the terms, acronyms or abbreviations that are used in the description herein. 6 TABLE 1 AAV Accountholder Authentication Value Access control server The Access control server services to validate the (ACS) enrollment of a specific cardholder account number (PAN) in 3-D Secure, as well as authenticate transactions. Accountholder Authentication Value Cardholder authentication data required for electronic (AAV) commerce transactions in which cardholder authentication has been successfully performed. Cardholder Authentication Cardholder authentication data required by Visa for Vuterication Va electronic commerce transactions in which cardholder Verification Value authentication has been successfully performed. (CAVA) ________________ Card Verification A two-part card security feature. CVC 1 is a 3-digit Code (CPC) value encoded on tracks I and 2 in three contiguous positions in the "discretionary data" field of a magnetic stripe on a card. CVC 2 differs from CVC 1 and is indent-printed into the tamper- evident signature panel on the card. The CVC is intended to inhibit the alteration or misuse of card data and enhance the authentication of the card. Message Cryptographically generated code that is a function of Authentication the message contents and a secret key shared by the Code (MAC) message originator and the message recipient. This value, generated by the originator and verified by the recipient, enables the recipient to detect any alteration to the original message. Secure Payment Specifications and algorithm for generating cardholder Application (SPA) authentication data from merchant and issuer data components resulting in the creation of an AA V. The universal multi-purpose data transport Universal Cardholder infrastructure and defined field that is used to (UAF)icommunicate and transport authentication information, (UCAF) including AAV, among various stakeholders in a transaction. SPA 135 may include cryptography algorithms (namely "HMAC" and "CVC2" algorithms) that are used to generate Cardholder Authorization Verification Values (CAVV) in formats that are compatible with 3-d Secure message formats. -7- SPA 135 may be integrated with any suitable authentication program that card issuers may choose or implement for authenticating their cardholders. The authentication programs may include smart card-based and password based solutions (e.g., FIG. I chip based authentication program 141 and 3-D Secure password-based 5 authentication program 142). The authentication programs also may include other solutions based, for example, on PC identification. An authentication program in which the inventive Secure Payment Applications (SPA 135) are utilized may be a solution or program for securing electronic transactions conducted on e-commerce platforms that are compliant with 10 the 3-D Secure protocols. For this purpose SPA 135 is designed to use and generate authentication results in data format that can e readily used in 3-D Secure messages. In particular, a formatted data structure with defined fields and byte length may be used to facilitate transportation of authentication results in 3-D Secure messages. For purposes of illustrating the application of SPA 135 in an 15 exemplary authentication program 1000 (FIG. 1), a card payment transaction is used herein as an exemplary transaction. The participants in the card payment transaction may include a cardholder, an issuer, a merchant and an acquirer. A cardholder is an authorized user of a payment card issued, for example, by a licensed member of authentication program 1000. The cardholder may 20 use the issued payment card to pay for an on-line transaction with a merchant. Authentication program 1000 may be part of an authentication program or services provided by a third party (e.g., MasterCard) who, for example, can ensure that the cardholder's identity and presence is properly authenticated prior to the completion of the transaction. 25 An issuer is a member (e.g., a financial institution) that issues the payment card, which may be branded (e.g., MasterCard@ and/or Maestro® cards). The issuer guarantees payment for an authorized transaction using the payment card in accordance with payment card brand regulations and local legislation. The issuer may be responsible for determining cardholder eligibility to participate in 30 authentication program 1000, in addition to providing authentication services to merchants or other parties. -8- A merchant is a retailer, or any other person, firm, or corporation who, for example, pursuant to a merchant subscription agreement, agrees to accept issuers' payment cards for payment when they are properly presented. By subscribing to authentication program 1000, a merchant can offer a cardholder an authenticated 5 electronic interaction over the Internet. A merchant who accepts payment cards may have a further relationship with an acquirer. Merchants who participate in authentication program 1000 may benefit in several ways including reduced fraud and dispute costs, increased transaction volume, protection from unauthorized card use, and access to the issuer's card base. 10 An acquirer is an entity who maintains relationships with merchants and acquires the data relating to a transaction from the merchant or card acceptor. The acquirer may be responsible for determining the merchant eligibility to participate in authentication program 1000. As shown in FIG. 1, exemplary authentication program 1000, may be 15 implemented as a secure e-commerce arrangement or platform with a number of layered components. The layered components include data transport layer 100, merchant requirement layer 120, authentication layer 130, and issuer platform 140. Authentication layer 130 relates to the Secure Payment Applications (SPA 135) that are deployed to authenticate a transaction or payment. 2.0 Data transport layer 100 relates to data collection and transport infrastructure that is used to communicate authentication information and results amongst the cardholder, issuer, merchant and acquirer. The data transport may, for example, based on standardized data structures, architectures or mechanisms such as the Universal Cardholder Authentication Field (UCAF). 25 UCAF may in general be defined as a variable length, 32-character field with a flexible data structure that can be tailored to support the needs of a variety of issuer security and authentication approaches. FIG. 2 shows a generic structure of UCAF. A first control byte in UCAF contains a value that is specific to each security payment application or aspect. The remainder of the bytes in UCAP may include 30 application specific data. An authentication or authorization provider may be -9responsible for assigning and managing UCAF control byte values and the structure of UCAF application specific data. An exemplary control byte definition may be as follows: 5 Usage 3-D Secure SPA AAV for first and subsequent transactions Base 64 Encoded Value j Hexadecimal Value x'8C' 10 Another exemplary control byte definition may be as follows: Usage 3-D Secure SPA AAV for attempts Base64 Encoded Value j Hexadecimal Value x'86' 15 In conventional UCAF implementations, the application specific data may be defined as binary data with a maximurn length of 24 binary bytes - including the control byte. However, some transaction authorization networks limit the passing of binary data in authorization messages. Accordingly, all UCAF data generated by SPA 135 in authentication program 1000 may be Base 64 encoded prior to inclusion 20 in an authorization message. The Base 64 encoding produces a character representation of the associated binary data. The resulting character representation is approximately a third larger than the binary equivalent. For this reason, the UCAF field may in general be defined with a maximum length of 32 characters. However for compatibility with 3-D Secure messaging in authentication program 1000, the 25 UCAF field is limited to 28 characters in length. The Accountholder Authentication Value (AAVT) is a specific implementation of UCAF related to issuer authentication platforms that incorporate the SPA. AAV may be generated by the issuer and presented to the merchant for placement in a transaction authorization request (to the acquirer) upon successful 30 authentication of the cardholder by the issuer. In the case of a chargeback or other potential dispute processing, AAV may be used to identify the processing parameters -10associated with the transaction. UCAF is the mechanism that is used to transmit the AAV from the merchant to issuer for authentication purposes during the authorization process. With renewed reference to FIG. 1, merchant requirement layer 110 5 relates to merchant capabilities for interacting with the other layers and the cardholder. Merchants participating in authentication program 1000 may implement application software capabilities (e.g., merchant plug-ins (MPI)) that are capable of processing 3-D Secure messages. A MPI may serve as the controlling application for the processing of 3-D Secure messages. 10 Authentication layer 130, which includes the inventive SPA 135, represents the authentication process or services (e.g., provided by or contracted for by an issuer) for verifying cardholder account ownership. An issuer using, for example, an access control server (ACS) may implement authentication layer 130/SPA135 in conjunction with an AAV validation server/process. 15 Exemplary e-commerce network components or entities that are involved in the authentication process may for purposes illustration be organized as belonging to issuer, acquirer or interoperability domains as shown in TABLE 2. TABLE 2 Issuer Domain Interoperability Domain Acquirer Domain Cardholder Browser Directory Server Merchant Plug-In Related Cardholder Software Certificate Authority Signature Validation Server Enrollment Server Access Control Server AAV Validation Server/Process 20 With reference to TABLE 2, the functionality present in the issuer domain includes a cardholder browser which can act as a conduit for transporting messages between the MPI (in the acquirer domain) and the access control server (in -11the issuer domain). Related cardholder software, for example, may include optional software to support use of smart cards. Thd enrollment server facilitates the process of cardholder enrollment for an issuer's implementation of 3-D Secure under authentication program 1000. The server may be used to perform initial cardholder 5 authentication, as well as for administrative activities such as resets and viewing 3-D Secure payment history. The access control server provides at least two basic functions during the course of an online purchase. First, ACS will verify whether a given cardholder account number is enrolled in program 1000. Secondly, ACS will conduct 10 authentication processes for cardholder identification. For this purpose, ACS may operate in conjunction with or include an AAV validation server/process. This AAV validation server/process also may be used to validate cardholder authentication data received from merchants or acquirers. The functionality in the acquirer domain may include the functions of a 15 Merchant Plug-in (MPI) and a signature validation server. The MPI may create and process payer authentication messages and then returns control to merchant software for further authorization processing. MPI authentication processes may be invoked after a cardholder submits a purchase request, including the account number to be used for payment, but prior to obtaining authorization for the purchase. The signature 20 validation server may be used to validate a digital signature on a purchase request that has been successfully authenticated by the issuer. The functionality in the interoperability domain may include a directory server. The directory server may be a global directory sever, which provides centralized decision making capabilities to merchants enrolled in the in 25 authentication program 1000. Based on the account number contained in a merchant verification request message, the directory may first determine whether the account number is part of a participating card issuer's card range. It may then direct eligible requests to the appropriate issuer's ACS for further processing. The interoperability domain also may include a suitable certificate authority for generating and distribute 30 all private hierarchy end-entity and subordinate certificates, as required, to the various components and to other subordinate certificate authorities across all three domains. -12- The cardholder authentication process in program 1000 involves exchanges of messages and data across the three domains. The following exemplary 3-D Secure inter domain messages may be used step-by-step in the authentication process: 5 (1) Verification Request/Response Message Pair: VEReq/VERes A first step in the authentication process is to check or validate that the cardholder account number is part of the card range of an issuer participating in authentication program 1000. For this purpose, a Verification Request message 10 VEReq, is sent from the MPI to the directory to check card range eligibility. If the specified account number is contained within an eligible card range in the directory, this message then may be forwarded from the directory to the issuer's ACS to further check if the specified account number is enrolled and/or activated by the issuer as a participant in program 1000. 15 The MPI may have an optional capability to locally cache card ranges by each participating issuer. In such cases, Card Range Request/Response messages may be used by the MPI to request updates to the card range caches from the directory. For merchants who cache card ranges, the VEReq/VERes messages may not be utilized if the local cache indicates that the issuer is not enrolled in 20 authentication program 1000. (2) Payer Authentication Request/Response Message Pair: PAReq/PARes Once it has been determined that the cardholder is enrolled by an issuer or is an active participant in program 1000, the process of authenticating the specific 25 cardholder further involves the specific card issuer. Payer Authentication Request/Response messages may be sent from the MIPI to the specific card issuer's ACS to perform authentication. At this stage of the authentication process in program 1000, the cardholder may be presented with an authentication window. The authentication window may be displayed on the cardholder browser and be populated 30 with relevant information by the issuer. The cardholder may be requested to enter a password, code or token for personal identification or authentication through the -13displayed authentication window. The specific card issuer's ACS may then use, for example, SPA 135 to authenticate the collected or entered information, and accordingly generate an Accountholder Authentication Value (AAV). The AAV is transported in the 3-D Secure PARes (Payer Authentication Response) message in a 5 designated Cardholder Authentication Verification Value (CAVV) field in an UCAF. CAAV is one of the data fields in the response portion of the message pair PAReq/PARes returned by the issuer to the requesting merchant. The issuer may place suitable digital signatures on their response. The merchant may, further, include the received AAV to an acquirer for forwarding to the issuer as part of a 10 payment/transaction authorization request (See e.g., FIG. 4). FIG. 3 schematically shows an exemplary card authentication process 300 for a cardholder transaction under authentication program 1000. For purposes of illustration, the description of process 300 assumes that cardholder 310 is enrolled by an issuer in authentication program 1000 and has obtained a password or code from 15 the issuer to use while shopping online at participating merchants. Process 300 also assumes that all communication channels between components (e.g., cardholder 310, MPI 320, directory 330 and issuer ACS 340) are properly secured using the Secure Socket Layer protocol (SSL) links (e.g., SSL-1, SSL-2, SSl-3, SSI-4, SSL-5 and SSL 6). 20 In process 300 at step 351, cardholder 310 may shop at a merchant web site and, when ready to checkout, enter payment card information (e.g., the account number) and other information (e.g., shipping information) via link SSL-1. Once all of the payment and shipping information has been entered, the merchant may give cardholder 310 an opportunity by to review the purchase before submitting an order. 25 Next at step 352, MPI 320 queries directory 330 via link SSL-2 to verify the enrollment of cardholder 310 with a specific issuer using the verification request message VEReq. Step 352 optionally may be performed locally at MIPI 320 via a local card directory cache. In responses to the VEReq message, directory 330 may determine that a particular issuer is participating, and accordingly forward a 30 request via link SSL-3 to the particular issuer's ACS 340 to check on the current enrollment status of cardholder 310. The resulting responses may flow back over the -14same links (e.g., SSL-3 and SSL-2) to MPI 320. If ACS 340 indicates that cardholder 310 is enrolled in program 1000, MPI 320 may create a Payer Authentication Request message and send it to the cardholder's browser at step 354 via link SSL-4. Next at step 355, the cardholder's browser may redirect the message to the appropriate issuer's 5 ACS 340 to initiate cardholder authentication. When ACS 340 receives the Payer authentication request message, it may cause a user authentication dialog to begin. As part of the user authentication dialog, ACS 340 may cause a separate interactive authentication window to be displayed to cardholder 310 to facilitate password, code or other data input by cardholder 310. 10 At step 356, ACS 340 (using SPA 135) may authenticate the password or code entered by cardholder 310. ACS 340 may construct a SPA AAV according to the authentication program provider's implementation of 3-D Secure. ACS 340 may build and digitally sign an appropriate payer authentication response message. The payer authentication response message is then returned (via link SSL'-6) to MPI 320. 15 The authentication window displayed to cardholder 320 may disappear at this point. After cardholder authentication process 300 has been completed, the merchant may be required to pass the received SPA AAV to the acquirer via the UCAF field within an authorization message. The SPA AAV may then passed along from the acquirer to the issuer as part of conventional authorization message 20 processing. When received by the issuer, the AAV can be validated as part of authorization request processing, and archived for use in resolving any cardholder disputes that may arise later on. Standard 3-D Secure version 1.0.2 message formats and data formats may be used for all data communications between the involved parties or entities. 25 Specifically, the SPA AAV that ACS 340 creates and returns back to the merchant for inclusion in UCAF messages is 28 characters long and contains a 20-byte field defined for 3-D Secure in base 64 encoding. TABLE 3 shows an exemplary data structure or format of a 20-byte SPA AAV. -15- TABLE 3 Length Byte Position Field Name Data Source: ACS (Bytes) Number 1 Control Byte The control byte is used to 1 Byte I indicate the format and content of the associated AAV structure. A hexadecimal value x'8C' may indicate an AAV created as the result of a successful cardholder authentication. A hexadecimal value x'86' may indicate an AAV created as the result of attempts processing. 2 Hash of The left most 8 bytes of an 8 Bytes 2 Merchant SHA-1 hash of the 9 Name Merchant Name field from the PAReq. 3 ACS This data field may allow 1 Byte 10 Identifier an issuer to use up to 256 different ACS facilities. Values for this field may defined based on the algorithm used to create the MAC: 0 - 7 Reserved for HMAC 8 - 15 Reserved for CVC2 16 -255 - Reserved for future use 4 Authenticatio Indicates how the % Byte 11, n Method cardholder was (4 bits) 1st hex authenticated to the ACS: digit 0 = No Cardholder Authentication Performed (valid only for an AAV created using control byte value x'86' - Attempts processing.) 1 = Password 2 = Secret Key (e.g. Chip Card) -16- Length Byte Position Field Name Data Source: ACS (Bytes) Number 5 BIN Key Indicates which one of the /2 Byte 11, Identifier possible 16 issuer-known (4 bits) 2nd hex secret keys for a given BIN digit range was used by the ACS identified by the ACS identifier to create the MAC. 6 Transaction Unique number that, can be 4 Bytes Sequence used to identify the (8 hex 12-15 Number transaction within the ACS digits) identified by the ACS identifier. Once the maxiinium value has been reached, the number should recycle back to 0. This number must be unique for every PARes created for a given ACS identifier for a given issuer during the time that a chargeback can occur. 7 MAC Message Authentication 5 Bytes Code, created by ACS. 16-20 Issuers providing both existing PC identification or other authentication solutions (e.g., FIG. 1) in addition to a 3-D Secure solution may differentiate between the AAV values they receive from different authentication 5 solutions in the corresponding authorization message. The 20-byte AAV (e.g., TABLE 2) resulting from 3-D Secure compatible program 1000 may differ from common28-byte AAV structures (i.e., in non 3-D Secure programs) in the following ways: The transaction amount and currency codes are not included in the 20-byte AAV as this information is included in the signed PARes message; A merchant 10 transaction stamp (MTS) is not included as a transaction identifier (XID), which is included in the signed PARes message, can provide the same functionality. Further, the hash of the merchant name field is expanded. As a result, only minimal edits of the merchant name may now be required prior to creating the SHA-1 hash. -17- A merchant may not have to modify the control byte for subsequent authorizations (e.g. split shipments). For split shipments, the merchant may resend an original AAV generated by 3-D Secure compliant implementations of program 1000. The control byte value in the 20-byte SPA AAV is based on the result 5 of the cardholder authentication request (PAReq). This result may be indicated in the transaction status field of the Payer Authentication Response (PARes) messages. TABLE 4 shows exemplary values of the transaction status field in a PARes message. TABLE 4 Transaction Control Byte First AAV Byte Authentication Status Value in AAV Value After Method Field in PARes (hexadecimal) Base64 Field in AAV Encoding Y x'8C' j Any defined value other than "No Cardholder Authentication Performed" A x'86' h Must be "No Cardholder Authentication Performed" N No AAV is to be generated for this status value U No AAV is to be generated for this status value i 10 The merchant name contained in the PAReq message may be edited prior to creating the merchant name hash. The edits may specifically address Universal Transformation Format (UTF-8) encoding but also reference Unicode characters for other encoding types. An edit may delete any UTF-8 byte sequence that does not have a 15 Unicode representation. Such an edit may delete any UTF-8 bytes beginning with binary 1111 and all subsequent bytes beginning with binary 10 -18- Another edit may delete any UTF-8 byte sequence or byte sequence with the following Unicode representation: 0000 through 001F (ASCI control characters; 007F through OOAO (DEL and CI control characters; 5 OOAD (soft hyphen); and 2000 through 206F (General Punctuation). Such an edit may delete the following UTF-8 bytes: Hex 00 through IF Hex 7F 10 Hex C2 80 through C2 AO Hex C2 AD Hex E2 80 through E2 81 AF Still another edit may delete any leading or trailing spaces (e.g., UTF-8 bytes Hex 20). 15 In the case of a chargeback or other potential dispute processing, the 20-byte AAV may be used to identify the processing parameters associated with the transaction. Among other things, the AAV field values may identify: * The physical location of where the transaction was processed. * The sequence number that can be used to positively identify the transaction 20 within the universe of transactions for that location -19- * The secret key used to create the MAC, which not only ensures AAV data integrity but also binds the entire AAV structure to a specific PAN for implementations of 3-D Secure. 5 Field dependencies in the AAV may be established to ensure proper identification of the processing parameters. These field dependencies may be considered when building or configuring issuer ACS installations. For every ACS configured with the same ACS identifier: 0 The BIN Key Identifier field must be unique for each BIN range processed by 10 the identified ACS. Most issuers may use a common set of keys for most or all of their BIN ranges. However, this configuration allows for flexibility in a choice of software vendors that support or issuers that require the use a separate set of keys. o The Transaction Sequence Number field must be unique for each AAV 15 generated by the identified ACS within the time that a chargeback can occur. ACS installations that have the capability to share BIN keys and a common set of transaction sequence numbers across multiple logical installations or physical machines may be advantageously configured to use the same ACS identifier. Alternatively, a separate ACS identifier or set of ACS identifiers may be required for 20 each installation. In cases where one ACS facility serves multiple issuers, more than one issuer may share an ACS identifier. In these cases, the BIN field value for the associated transaction may become a determining factor in interpreting the field content location. Particular algorithms may be utilized in SPA 135 to create a Merchant 25 Authentication code (MAC) value. For example, an "HMAC" algorithm or an "CVC2" algorithm may be used by the ACS identified by the ACS identifier sub field to create MAC values. -20- The HMAC algorithm generates a MAC value cryptographically based on a secret key identified by the BIN Key Identifier sub field. This secret key is shared with the issuer and binds the cardholder account number to the AAV by the concatenation of the following data: 5 e The account number, as received by the ACS in the Verification Request (VEReq) message that corresponds to the current Payer Authentication Request (PAReq) message. The account number may be represented as binary-coded decimal, left justified and padded on the right with hexadecimal 'Fs to a length of 20 digits (10 total bytes). 10 * The left-most 15 bytes, fields 1 through 6, of the AAV being constructed. The secret key length may be optionally selected be a minimum of 128 bits (16 bytes) and a maximum of 192 bits (24 bytes). Any intervening key size (e.g. 160 bits) may be acceptable. The actual key length size used may be independently selected by each implementation. The MAC field within the SPA AAV defined for a 15 3-D secure authentication program (e.g., Program 1000) may be populated with the left-most 40 bits (5 binary bytes) of the cryptographic result obtained by applying algorithm HMAC. EXAMPLES I and 2 illustrate the application of the H1MAC algorithm using 20 byte and 16 byte keys, respectively, to generate SPA AAV values. 20 EXAMPLE 1 (20 Byte Key) Assumed account number: 5432 109876543210 Assumed Merchant Name: SPA Merchant, Inc. (All ASCII characters, and no editing required) Assumed AAV control byte = 8C -21- First 8 bytes, SHA-I hash of Merchant Name = 7CA7 FBB6 058B 5114 Assumed ACS Id = 01 Assumed Authentication Method = 1 (Password) Assumed BIN Key Id = I 5 Assumed Transaction Sequence Number = 0000002F Assumed key (20 Bytes) = OBOBOBOBOBOBOBOBOBOBOBOBOBOBOBOBOBOBOBOB Therefore SHA-1 HMAC is based on 5432 109876543210 FFFF 8C 7CA7FBB6058B5114 0111 0000002F 10 This produces a MAC whose first 5 bytes are: 3547 BAIE FF Therefore, the complete AAV in hex is: SC 7CA7FEB6058B5114 0111 0000002F 3547BAIEFF after Base-64-encoding, this is: 15 jHyn+7YFiIEUAREAAAAvNUe6Hv8= EXAMPLE 2 (16 Byte Key) Assumed account number: 5432 109876543210 Assumed Merchant Name: SPA Merchant, Inc. (All ASCII characters, and no editing required) 20 Assumed AA V control byte = 8C First 8 bytes, SHA-1 hash of Merchant Name = 7CA7 FBB6 058B 5114 -22- Assumed ACS Id = 01 Assumed Authentication Method = I (Password) Assumed BIN Key Id = I Assumed Transaction Sequence Number =0000002F 5 Assumed key (16 Bytes) = 00112233445566778899AABBCCDDEEFF Therefore SHA-1 HMAC is based on 5432 109876543210 FFFF 8C 7CA7FBB6058B5114 0111 0000002F This produces a MAC whose first 5 bytes are: EB27 FC7F AB 10 Therefore the complete AAV in hex is: SC 7CA7FBB6058B5114 0111 0000002F EB27FC7FAB after Base-64-encoded, this is: jHyn+ 7YFil EUAREAAAA v6yff6s= The CVC2 algorithm also Cryptographically creates the MAC field 15 values. In contrast to the HMAC algorithm, which uses one key, the CVC2 algorithm use two 64 bit DES keys identified by the BIN Key Identifier sub field. In the CVC2 algorithm, all encryption and decryption steps may use Electronic Code Book (ECB) form of DES. The CVC2 algorithm generates a three digit 3 digit CVC2 value. The 20 input data which is processed by CVC2 algorithm for generating this three digit 3 digit CVC2 value is shown in TABLE 5. TABLE 5 -23- CVC2 Field MAC Field Data Source Length Name Name (Digits) Primary Primary The account number, as 13 to 19 digits Account Account presented in the Number Number Verification Request (VEReq) message Card Transaction Convert Transaction 4 digits Expiration Sequence Sequence Number, as Date Number contained in AAV, to BCD decimal equivalent. Populate this field with the 4 least significant digits. Any value less than 4 digits should be right justified in the field and padded with binary zeros to 4 digits. Service Authenticatio Authentication Method I digit Code n as contained in the AAV. Method If the value of the Authentication Method sub field is greater than 9, subtract 10 to obtain the digit to be used. Control Byte Convert Control Byte, as 2 digits contained in the AAV, to BCD decimal equivalent. Populate this field with the 2 least significant digits. The resultant three digit CVC2 value is converted to binary coded decimal form and populated in the left most two bytes of the MAC sub field with a leading binary 0 used to fill the first unused half byte. The remaining thee bytes of 5 the MAC sub field may be filled with binary zeros. For example: CVC2 = 123 MAC sub field = 0123000000 (10 total digits). EXAMPLE 3 and TABLE 6 illustrate the application of the CVC2 algorithn and the process steps involved in application of the algorithm to generate SPA AAV values. -24- EXAMPLE 3 Assumed account number: 5432109876543210 Assumed Merchant Name: SPA Merchant, Inc. (All ASCII characters, and no editing required) 5 Assumed AA V control byte = 8C First 8 bytes, SHA-1 hash of Merchant Name = 7CA7 FBB6 058B 5114 Assumed ACS Id = 7 Assumed Authentication Method = 1 (Password) Assumed BIN Key Id = 1 10 Assumed Transaction Sequence Number = 0000002F Key A = 0011223344556677 Key B= 8899AABBCCDDEEFF Therefore, the CVC2 algorithm calculation is based on Account Number = 5432109876543210 Expiration Date = 0047 Service Code= 140 15 This produces a CVC2 three digit value = 439 (see Table 6 for calculation): Based on the calculated CVC2 value, the MAC field = 0439000000 Therefore, the complete AA V in hex is: 8C 7CA7FBB6058B5114 01 11 0000002F 0439000000 Base-64-encoded, this is: 20 jHyn+7YFil EUAREAAAAvBDkAAAA= -25- The processing or calculation steps that are used in EXAMPLE 3 are shown in TABLE 6 TABLE 6 Step Processing Step Example Construct string of bits by 54321098765432100047140 concatenating (left to right) 1. the right-most 4 bits of each character of the specified data elements. Place the results in a 128-bit field, padding on the right 54321098765432100047140000000000 2. with binary zeros to fill all Block I = 5432109876543210 remaining bits. Split the 128- Block 2 = 0047140000000000 bit block into 2 64-bit blocks. Encrypt Block 1 using Key A Block 1 = 5432109876543210 3. Key A = 0011223344556677 Result = 44DD7C814CC62702 XOR the results of Step 3 with Block 2= 0047140000000000 Block 2. Step 3 44DD7C814CC62702 4. Encrypt this value using Key A. Result = Result = 449A68814CC62702 Decrypt the result of step 4 Step 4 449A68814CC62702 using Key B. Result = 5. KeyB 8899AABBCCDDEEF F Result = 191DCA3149A5BD51 Encrypt the result of step 5 Step 5 191DCA3149A5BD51 using Key A. Result = 6. Key A = 0011223344556677 Result = 4F AB392CE3C98B41 From the result of step 6, 439239841 going from left to right, 7. extract all numeric digits (0 9); left justify these digits in a 16-position field -26- From the result of step 6, 012421 going from left to right, 8. extract all characters of A through F. To compensate for decimals, subtract 10 from each extracted digit. Concatenate the digits from 439239841012421 9. step 7 to the right of the digits extracted in step 8. Select from the first three left- 439 10. most digits of the CVC. As defined by the 3-D Secure protocol, all PARes messages returned to the merchant are digitally signed by the associated cardholder's issuer ACS. The merchant may be required to validate the digital signature prior to extracting the SPA 5 AAV from the PARes message for inclusion in an authorization request sent to the acquirer. If an issuer supports both implementation of 3-D Secure and other authentication platforms (e.g., PC Authentication platforms) it may be necessary to distinguish between the two authentication platforms during processing of the authorization request message. This may be accomplished in one of two ways: 10 1. The first base64 encoded character is a. "j" or "h" for the SPA AAV within the defined implementation of 3-D Secure b. "g" or "A" for the PC Authentication SPA AAV 2. The control byte, converted to binary, is either 15 a. hexadecimal8C or hexadecimal 86 for the AAV defined for MasterCard's implementation of 3-D Secure -27b. hexadecimal 82 or hexadecimal 02 for the PC Authentication SPA AA V. Each issuer participating in program 1000 may assure that the ACS identifier sub field is appropriately set to indicate the algorithm used to create the 5 MAC. Failure to set this indicator correctly may result in improper validations during the transaction/payment authorization process. Although the present invention has been described in connection with specific exemplary embodiments, it should be understood that various changes, substitutions, and alterations apparent to those skilled in the art could be made to the 10 disclosed embodiments without departing from the spirit and scope of the invention. -28-