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    Glossary
    3RI Payment
            The EMV 3-D Secure request for information. It is an EMVCo term for the EMV 3-D
                Secure service that can check a BIN without performing a complete
                authentication.
3-D Secure
            Security protocol for online credit card and debit card
                transactions used by Visa Secure, Mastercard Identity Check, American
                Express SafeKey, JCB J⁄Secure, Diners Club ProtectBuy, Discover
                ProtectBuy, China UnionPay, and Elo.
AAV
            Account Authentication Value. A unique 32-character transaction token for a
                3-D Secure transaction. For Mastercard Identity Check, the AAV is named the
                UCAF. For Visa Secure, the AAV is named the CAVV.
acquirer
            The financial institution that accepts payments for products or services on behalf of
                a merchant. Also referred to as the acquiring bank. This bank accepts or acquires
                transactions that involve a credit card issued by a bank other than itself.
acquirer BIN
            An eight-digit number that uniquely identifies the acquiring bank. Every
                participating acquirer has a different acquirer BIN. The Mastercard BIN starts with
                5 and the Visa BIN starts with 4.
acquirer processor
            Processor that provides credit card processing, settlement, and services to  merchant banks.
ACS
            Access Control Server. The card-issuing bank’s host for the
                payer authentication data.
ACS URL
            The URL of the Access Control Server of the card-issuing bank that is returned in the
                response to the request to check enrollment. You send the PAReq to this URL so that
                the customer can be authenticated.
American Express
            A globally issued card type that starts with 3 and which is identified as card type
                003. These cards participate in a card authentication service (SafeKey) provided by
                EMV 3-D Secure.
authentication result
            Raw data sent by the card issuer that indicates the status of authentication. You do
                not need to pass this raw data into the authorization.
Base64
            Standard encoding method for data transfer over the internet.
BIN
            Bank Identification Number. The eight-digit number that identifies the card
                issuer.
CAVV
            Cardholder Authentication Verification Value. A Base64-encoded string sent back with Visa
                Secure-enrolled cards that specifically identifies the transaction with
                the issuing bank and Visa. Standard for collecting and sending AAV data
                for Visa Secure transactions. See AAV.
CAVV algorithm
            The method used to generate the CAAV value.
Compra Segura
            Trademarked name for the Elo card authentication service.
CVV
            Card Verification Value. Security feature for credit cards and debit cards. This
                feature consists of two values or codes: one that is encoded in the magnetic strip
                and one that is printed on the card. Usually, the CVV is a three-digit number on the
                back of the card. The CVV for American Express cards is a 4-digit number on the
                front of the card. CVVs are used as an extra level of validation by issuing
                banks.
Diners Club
            A globally issued card type whose numbers start with a 3 or a 5. Diners Club cards
                are identified as card type 005. These cards participate in a card authentication
                service (ProtectBuy) provided by 3-D Secure.
Directory Servers
            The Visa and Mastercard servers that are used to verify
                enrollment in a card authentication service.
Discover
            Primarily, a U.S. card type starting with a 6. Discover cards are identified as card
                type 004. These cards participate in a card authentication service (ProtectBuy)
                provided by 3-D Secure.
ECI (ECI Raw)
            The numeric commerce indicator that indicates to the bank
                the degree of liability shift achieved during payer authentication
                processing.
E-Commerce Indicator
            Alpha character value that indicates the transaction type,
                such as MOTO or INTERNET.
Elo
            A globally issued card type starting with a 5. Elo cards are identified as card type
                of 054. These cards participate in a card authentication service (Compra Segura)
                provided by 3-D Secure.
Enroll
            A type of transaction used for verifying whether a
                card is enrolled in the Mastercard Identity Check or Visa Secure service.
HTTP
            The Hypertext Transfer Protocol is an application protocol used for data transfer on
                the internet.
HTTP POST request
            POST is one of the request methods supported by the HTTP protocol. The POST
                request method is used when the client sends data to the server as part of
                the request, such as when uploading a file or submitting a completed
                form.
HTTPS
            Hypertext Transfer Protocol combines with SSL/TLS (Secure Sockets
                Layer/Transport Layer Security) to provide secure encryption of data
                transferred over the Internet.
issuer
            The bank that issues the credit card.
J/Secure
            The EMV 3-D Secure program of JCB.
JCB
            Japan Credit Bureau. A globally issued card type starting with a 3. JCB cards are
                identified as a card type of 007. These cards participate in a card authentication
                service (J/Secure) provided by EMV 3-D Secure.
Maestro
            A card brand owned by Mastercard that includes several debit card BINs within the
                U.K. and in Europe. Merchants who accept Maestro cards online are required to use
                Mastercard Identity Check, Mastercard’s card authentication service. Maestro cards
                are identified as 024 and 042 card types. Note that many international Maestro cards
                are not set up for online acceptance and cannot be used even if they participate in
                a Mastercard Identity Check authentication program.
Mastercard
            A globally issued card that includes credit and debit cards. These cards start with a
                5. These cards are identified as card type 002 for both credit and debit cards.
                These cards participate in a card authentication service (Mastercard Identity Check)
                provided by 3-D Secure.
Mastercard Identity Check
            Trademarked name for Mastercard’s payer authentication service.
MD
            Merchant-defined Data that is posted as a hidden field to the ACS URL. You can use
                this data to identify the transaction on its return. This data is used to match the
                response from the card-issuing bank to a customer’s specific order. Although payment
                card companies recommend that you use the XID, you can also use data such as an
                order number. This field is required, but including a value is optional. The value
                has no meaning for the bank and is returned to the merchant as is.
Merchant ID
            Data that must be uploaded for the Mastercard and Visa card
            authentication process for each participating merchant. The Merchant ID
            is usually the bank account number or it contains the bank account
            number. The data is stored on the Directory Servers to identify
            the merchant during the enrollment check.
MPI
            Merchant Plug-In. The software used to connect to Directory Servers and to decrypt the PARes.
PAN
            Primary Account Number. Another term for the credit card number.
PAReq
            Payer Authentication Request. Digitally signed Base64-encoded payer authentication
                request message, containing a unique transaction ID that a merchant sends to the
                card-issuing bank. Send this data without alteration or decoding. Note that the
                field name has a lowercase “a” (PaReq), but the message name has an uppercase “A”
                (PAReq).
PARes
            Payer Authentication Response.  A compressed, Base64-encoded response from the card-issuing bank.
                This data is passed for validation.
PARes status
            Payer Authentication Response status. One-character length
                status passed back by Visa and Mastercard that is required data for
                Asia, Middle East, and Africa Gateway authorizations.
processor
            Financial entity that processes payments. Also see 
acquiring processor
.ProofXML
            This field contains the VEReq and VERes messages for merchant storage. Merchants can
                use this data for potential chargeback repudiation.
ProtectBuy
            Trademarked name for the Diners Club and Discover card
                authentication services.
request ID
            A 22- or 23-digit number that uniquely identifies each
                transaction. Merchants should store this number for
                future reference.
risk-based authentication
            Risk-based authentication is provided by the card-issuing bank. The card-issuing bank
                gathers a cardholder’s transaction data or leverages whatever data they have to
                silently authenticate the cardholder based on the perceived degree of risk. They
                base their risk assessment on factors such as cardholder spending habits, order or
                product velocity, the device IP address, order amount, and so on.
SafeKey
            Trademarked name for the American Express card authentication service.
SCMP API
            A legacy name-value pair API that was superseded by the Simple Order API.
Simple Order API
            An API, that provides three ways to access services: name-value pair (NVP), XML, and
                SOAP.
TermURL
            Termination URL on a merchant’s website where the
                card-issuing bank posts the payer authentication response (PARes)
                message.
UCAF
            Universal Cardholder Authentication Field. A Base64-encoded string sent back with
                Mastercard Identity Check enrolled cards specifically identifying the transaction
                with the issuing bank and Mastercard. Standard for collecting and sending AAV data
                for Mastercard Identity Check transactions. See also 
AAV
.UCAF collection indicator
            Value of 
1
 or 2
 that indicates whether a Mastercard
                cardholder has authenticated themselves.validate
            A service that decodes and decrypts the PARes message to determine success. The
                validate service returns the needed values for authorization.
VEReq
            Verify Enrollment Request. Request sent to the Directory Servers to verify that a card is enrolled in a card authentication service.
VERes
            Verify Enrollment Response. Response from the Directory Servers to the VEReq.
VERes enrolled
            Verify Enrollment Response enrolled. One-character length
                status passed back by Visa and Mastercard that is required data for
                Asia, Middle East, and Africa Gateway authorizations.
Visa
            A globally issued card that includes credit and debit cards. These card numbers start
                with a 4. These cards are identified as card type 001 for both credit and debit
                cards. These cards participate in a card authentication service (Visa Secure)
                provided by EMV 3-D Secure.
Visa Secure
            Trademarked name for Visa’s card authentication service.
XID
            String used by both Visa and Mastercard, that identifies a specific transaction on
                the Directory Servers. This string value should remain consistent throughout a
                transaction’s history.