> 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-android/implement-nfc-wallet/make-payment/implement-contactless-payments/7.-configure-cdcvm-experiences/pure-cdcvm/pure-cvm-priority.md).

# PURE CVM priority

## Overview

PURE CVM selection is a negotiation between the **digital wallet application** and the terminal.

It determines the Cardholder Verification Method (CVM) used to authenticate the **end user**.

This page describes the CVM selection process based on the supported CVM options and the configured CVM priority.

## CVM selection process

A PURE profile defines the supported CVMs and the CVM priority.

It uses the `PURE application control` field, byte 1 or byte 3:

* Byte 1 defines the CVM options associated with CIAC-CVM1.
* Byte 3 defines the CVM options associated with CIAC-CVM2.

{% hint style="info" %}
NFC Wallet SDK requires the same CVM options for CIAC-CVM1 and CIAC-CVM2.
{% endhint %}

When a transaction requires CVM, the selection process chooses the first CVM supported by both the digital wallet application and the terminal.

The following parameters are used for CVM selection.

### `PURE application control` details

The `PURE application control` field is a PURE profile value.

<table><thead><tr><th width="166.22216796875">Bit mapping</th><th>Description</th></tr></thead><tbody><tr><td>Byte 1 bit 6</td><td>1b: Local CDCVM is supported.</td></tr><tr><td>Byte 1 bit 4</td><td>1b: Signature is supported.</td></tr><tr><td>Byte 1 bit 3</td><td>1b: Online PIN is supported.</td></tr><tr><td>Byte 1 bit 1</td><td><ul><li>1b: Online PIN is preferred over CDCVM.</li><li>0b: CDCVM is preferred over online PIN.</li></ul></td></tr></tbody></table>

### `TTPI` details

If the PURE profile supports `TTPI` (Terminal Transaction Processing Information), the terminal advertises its supported CVM capabilities through this field.

<table><thead><tr><th width="162.88885498046875">Bit mapping</th><th>Description</th></tr></thead><tbody><tr><td>Byte 1 bit 3</td><td><p>Terminal capability: Support of Online PIN.</p><ul><li>1 = Online PIN is supported.</li><li>0 = Online PIN is not supported.</li></ul></td></tr><tr><td>Byte 1 bit 2</td><td><p>Terminal capability: Support of Signature.</p><ul><li>1 = Signature is supported.</li><li>0 = Signature is not supported.</li></ul></td></tr><tr><td>Byte 2 bit 7</td><td><p>Terminal request related to cardholder verification.</p><ul><li>1 = CVM is required.</li><li>0 = CVM is not required.</li></ul></td></tr><tr><td>Byte 3 bit 7</td><td><p>Terminal capability: Supports Consumer Device CVM as a possible CVM method when terminal requests for the cardholder verification in byte 2 bit 7.</p><ul><li>1 = The terminal supports CDCVM as a possible CVM.</li><li>0 = Terminal does not consider CDCVM as a possible CVM.</li></ul></td></tr></tbody></table>


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