# Adding an OPC UA Client certificate

Establishing a secure connection between OPC UA Server and OPC UA Client requires both parties to have the others certificate.

1. Prerequisite
2. You need a valid OPC UA Client certificate (X.509 public key certificate, additional entries according to the OPC UA specification, DER-encoded).

1. All added certificates will be trusted.

2. In the Data settings, click Client certificates.
3. The Trusted certificates list is displayed.
4. Click the plus icon.
5. Navigate to the certificate in your file system.
6. Click Open.

1. The certificate is added to the Trusted certificates list.