> 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/implement-nfc-wallet/make-payments/understand-cdcvm.md).

# Understand CDCVM

### Why CVM matters

CVM (Cardholder Verification Method) confirms the end user before a payment. It helps prevent unauthorized payments from a lost or stolen device.

### CDCVM (Consumer Device CVM)

CDCVM is one CVM method using the secure local device authentication method.

The iOS NFC Wallet SDK supports **CDCVM only**. It relies on iOS authentication to secure contactless payment transactions.

NFC Wallet SDK supports multiple CDCVM policies. Configure the policy during [NFC Wallet SDK initialization](/nfc-wallet-sdk-ios/get-started/configuration/3.-initialization.md#cardholder-verification-method):

* biometrics only
* biometrics with fallback to device passcode
* device passcode only (for example, if biometrics are unavailable)

On iPhone, biometrics means **Face ID** or **Touch ID**.

Refer to section [Local Authentication](https://developer.apple.com/documentation/localauthentication?utm_source=chatgpt.com) in Apple Developer Documentation.

{% hint style="warning" %}
Consider that end user can change the device unlock method. See [Device unlock method update scenario](/nfc-wallet-sdk-ios/implement-nfc-wallet/make-payments/understand-cdcvm/device-unlock-method-update-scenarios.md).
{% endhint %}

### Operational note

Even if the digital card profile defines a different CVM method, contactless transactions require CDCVM.

Check the digital card profile CVM method early. This helps you design the expected payment user experience.

{% hint style="warning" %}
The digital card profile CVM method can be CDCVM or Online PIN.

Mastercard calls Online PIN “card-like experience”.

NFC Wallet SDK supports one CVM method per digital wallet application.
{% endhint %}


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