# Additional Information
source: https://developer.mastercard.com/masterpass-merchant-integration-v7/documentation/additional-information/index.md

## 3D Secure {#3d-secure}

When using Masterpass checkout, you have the option to do either Basic Checkout Services (BCS) or Advanced Checkout Payer Authentication Services (ACPAS).

BCS is a core Masterpass offering and facilitates a simple, secure checkout experience for your consumers. ACPAS provides you an additional service to authenticate transactions with the consumer's payment card issuer using the 3D Secure protocol provided through the Mastercard® SecureCode™ or Verified by Visa programs.

#### Basic Checkout Services (BCS) {#basic-checkout-services-bcs}

When consumers select their payment method during Masterpass checkout, the payment method is returned to the merchant for completion.  

No additional enrollment steps are required for merchant integration with BCS as it is part of the core Masterpass Online Services.

#### Advanced Checkout Payer Authentication Services (ACPAS) {#advanced-checkout-payer-authentication-services-acpas}

For ACPAS, Masterpass will attempt to authenticate the consumer's payment card with their card issuer on your behalf, using Mastercard SecureCode for Mastercard or Maestro cards or Verified by Visa for Visa cards. A merchant can enable this service for each supported card brand offered, such as Mastercard, Visa, or both.

Before ACPAS can be performed for Masterpass checkout, you will need to complete the following:

1. Enroll in the Mastercard SecureCode or Verified by Visa program with your acquirer.
2. Opt in to 3D Secure transactions in the Masterpass portal. You are responsible for providing accurate Acquirer data to Mastercard in connection with your Masterpass enrollment and for updating such information on a timely basis should it change.
3. Provide accurate enrollment data to Mastercard---without it, you cannot receive the benefits of the ACPAS or of the associated Programs. You are responsible for submitting correctly formatted authorization and clearing ecommerce values to their payment processor to indicate use of the Mastercard SecureCode or Verified by Visa as defined by the programs. Specifically, ECI and CAVV (if present) must be amended to the Authorization request.

## Wallet Indicator Flag {#wallet-indicator-flag}

A three-byte wallet Indicator (WID) walletID parameter is returned in the PaymentDataApi and ExpressCheckoutApi responses. This value must be passed to your acquiring bank, and will indicate that the consumer's payment details were provided by the Masterpass service, rather than being manually entered. You may need to work with your payment provider (acquirer, payment gateway, and so on) to understand how best to handle this data element. In the event, your acquirer has not completed implementation of this element, your transactions will continue to process as-is.  

The following message elements in the Dual Message System (Authorization and Clearing) and Single Message System carry this WID Flag:

* Dual Message System (Authorization)---Data element (DE) 48 (Additional Data---Private Data), subelement 26 (Wallet Program Data), subfield 1 (Wallet Identifier)
* Dual Message System (Clearing)---PDS 0207 (Wallet Identifier)
* Single Message System---DE 48 (Additional Data), subelement 26 (Wallet Program Data), subfield 1 (Wallet Identifier)