> For the complete documentation index, see [llms.txt](https://docs.payments.thalescloud.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.payments.thalescloud.io/nfc-wallet-sdk-ios/additional-features/configure-visa-cvm-priority.md).

# Configure Visa CVM priority

## Overview

Visa CVM processing is a negotiation between the digital wallet application and the terminal. It determines which CVM (Cardholder Verification Method) is used to authenticate the end user for a transaction.

Set the CVM priority during SDK initialization by configuring `VISA_ONLINEPIN_PRIORITY` in your PLIST file. For details, see [Configure PLIST file](/nfc-wallet-sdk-ios/get-started/configuration/3.-initialization.md#configure-plist-file).

Based on this priority, the NFC Wallet SDK selects the best CVM supported by both:

* the digital card profile (CAP)
* the terminal (TTQ)

### Inputs used for CVM selection

#### CAP (card capabilities)

The supported CVMs per AID for a Visa contactless profile are defined by Card Additional Processes (CAP):

<table><thead><tr><th width="192.75">Bit mapping</th><th>Description</th></tr></thead><tbody><tr><td>Byte 3 bit 8</td><td>1b: Online PIN is supported for domestic transactions.</td></tr><tr><td>Byte 3 bit 7</td><td>1b: Online PIN is supported for international transactions.</td></tr><tr><td>Byte 3 bit 5</td><td>1b: Signature is supported.</td></tr><tr><td>Byte 3 bit 4</td><td>1b: CDCVM is supported.</td></tr></tbody></table>

#### TTQ (terminal capabilities)

The terminal uses Terminal Transaction Qualifier (TTQ) to indicate what it supports. The bit values are defined as follows:

<table><thead><tr><th width="196.5">Bit mapping</th><th>Description</th></tr></thead><tbody><tr><td>Byte 1 bit 3</td><td>1b: Online PIN is supported.</td></tr><tr><td>Byte 1 bit 2</td><td>1b: Signature is supported.</td></tr><tr><td>Byte 3 bit 7</td><td>1b: CDCVM is supported.</td></tr><tr><td>Byte 2 bit 7</td><td>1b: CVM is required. (HVT)</td></tr></tbody></table>

#### “Commonly supported” CVM

A CVM is *commonly supported* when it is supported by both the card profile (CAP) and the terminal (TTQ).

### Online PIN priority <a href="#online_pin-priority" id="online_pin-priority"></a>

1. Check whether CVM is required (`TTQ Byte 2 bit 7 == 1b`).
   * If false, proceed as a low-value transaction.
   * If true, continue with step 2.
2. Check if `ONLINE_PIN` is commonly supported.
   * If true, continue payment processing using Online PIN.
   * If false, continue with step 3.
3. Check if `Device CVM` is commonly supported.
   * If true, continue payment processing using CDCVM.
   * If false, continue with step 4.
4. Check if `SIGNATURE` is commonly supported.
   * If true, continue payment processing using signature.
   * If false, no commonly supported CVM exists. The terminal may require POS verification or reject the transaction.

### CDCVM priority <a href="#cdcvm-priority" id="cdcvm-priority"></a>

1. Check if `Device CVM` is commonly supported.
   * If true, continue with step 2.
   * If false, continue with step 3.
2. Check if CAP supports CDCVM and if CVM is required (`TTQ Byte 2 bit 7 == 1b`).
   * If true, proceed to authenticate the high-value transaction.
   * If CAP supports CDCVM but CVM not required `(TTQ Byte 2 bit 7 == 0b)`, proceed with the low-value transaction.
   * If CAP does not support CDCVM, continue with the payment processing using the `CARD_LIKE`.
3. Check whether CVM is required (`TTQ Byte 2 bit 7 == 1b`).
   * If false, proceed as a low-value transaction.
   * If true, continue with step 4.
4. Check if `ONLINE_PIN` is commonly supported.
   * If true, continue payment processing using Online PIN.
   * If false, continue with step 5.
5. Check whether `SIGNATURE` is commonly supported.
   * If true, continue payment processing using signature.
   * If false, no commonly supported CVM exists. The terminal may require POS verification or reject the transaction.


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