Partner Secure Elements (PSE) Integration

Overview

If you want to display sensitive information, such as card numbers, in your front-end, you'll need to interact with our Partner Secure Elements (PSE) service. The easiest way to do this is by using the PSE SDK from Gnosis Pay.

To initialize the SDK, you'll need an App ID provided to you upon registration with Gnosis Pay. You'll also need an ephemeral-token. This ephemeral-token can be retrieved with a call to our private PSE API using mTLS authentication.

caution

An mTLS authentication can only be performed from a back-end. For this reason, you need a back-end responsible for retrieving the ephemeral-token and sending it to your front-end upon request. We'll go through each step in this guide.

Once your front-end has the ephemeral-token, it can initialize the PSE SDK and use it to display secure elements.

Here's a diagram showing each step:

Reference implementations are available for a front-end and a back-end.

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Secure Connection Using mTLS Authentication

Mutual TLS (mTLS) is a type of authentication in which two parties in a connection authenticate each other using the TLS protocol. Your back-end will establish an mTLS authentication with the Gnosis Pay private PSE API to receive an ephemeral-token.

How to Generate mTLS Certificates

After signing up as a Gnosis Pay Partner, you will receive an App ID, which will be used in the certificate generation below. You must first create a private key and then generate a Certificate Signing Request (CSR) using the App ID as follows:

# APP_ID is a string starting with `gp_` that you have received from Gnosis Pay
export APP_ID="gp_woop_123"

# Create a private key (NEVER share with anyone)
openssl ecparam -name prime256v1 -genkey -noout -out "${APP_ID}.key.pem"

# Create the CSR (OK to share)
openssl req -new -sha256 -key "${APP_ID}.key.pem" -out "${APP_ID}.csr.pem" -subj "/CN=${APP_ID}"

You can now share the ${APP_ID}.csr.pem file with the Gnosis Pay team. DO NOT EVER share the .key.pem file with ANYONE.

Once we receive your Certificate Signing Request, we will sign it and send you back the signed certificates. These signed certificates, along with your private key, are used to establish the connection with the PSE API.

How to Establish an mTLS Authentication (in Node.js)

You should securely store the certificates in your environment along with your private key.

Your environment should expose the certificates and private key, for example:

SIGNED_CERTIFICATES="-----BEGIN CERTIFICATE-----
ABCQz ....
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
DEFC7 ....
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
GHICc ....
-----END CERTIFICATE-----"

PRIVATE_KEY="-----BEGIN EC PRIVATE KEY-----
ABCD....
-----END EC PRIVATE KEY-----"

Here's a Node.js implementation to request the ephemeral-token:

const httpsAgent = new https.Agent({
    cert: process.env.SIGNED_CERTIFICATES,
    key: process.env.PRIVATE_KEY,
    rejectUnauthorized: true, // Ensure SSL verification
});

const ephemeralTokenRequest = await axios({
    httpsAgent: httpsAgent,
    method: "POST",
    url: `https://api-pse.gnosispay.com/api/v1/ephemeral-token`,
    headers: { "Content-Type": "application/json" },
});

Please refer to our API documentation on the PSE service for more information about the specific endpoint.

info

The ephemeral-token, as its name suggests, is valid for a very short time frame. It is advised to generate a new one for every usage of the SDK.

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How to Use the PSE SDK

The PSE SDK will help you display sensitive information. It injects secure iframes into your front-end and exposes callbacks to interact with it. Refer to the PSE SDK documentation for instructions and examples.

How to Customize the Style of Secure Elements in the iframe

For security reasons, the only way to apply custom styling to iframe elements is to prepare and share a CSS file with the Gnosis Pay team. This file, named <partner_name>.css, will be incorporated into the iframe.

Standard styling is applied to the iframe elements by default. You can override the style of these classes and IDs as needed. Here are some of them:

Card Data

• .pse-container - A shared class for all iframe containers.
• #pse-card-data-container - The main container for displaying card data.
• .pse-card-field - The container for each card data field (card number, expiry date, security code).
• .pse-card-label - Labels for each field.
• .pse-card-value - The container for the actual card data values.

Set PIN Form

• .pse-container - A shared class for all iframe containers.
• #pse-set-pin-form - The main form container.
• #pse-set-pin-success-container - The success state container.
• .pse-set-pin-container - The base container class.
• .pse-set-pin-button - The base class for all buttons.
• #pse-continue-pin-button - The continue button.
• #pse-done-button - The done button.

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Guide

Here is a suggested workflow to customize the styling:

1. In your front-end, load the element you wish to customize (e.g., the card data).
2. Locate the custom CSS file with your name in either the "Style Editor" in Firefox or the "Sources" panel on Chrome/Brave. In the example below, the file is gnosis_pay_ui.css.
3. Apply your desired styling. The changes will be reflected in your interface immediately.
4. Save the file and send it to Gnosis Pay for application in production.

Here is an example of overriding the .pse-card-field class in Firefox: