We’re evaluating OPC UA on our site. We have a simple OPC UA server and using the Prosys OPC UA client to test the connection.

For the User Security component – when using ‘Anonymous or Username/Passwords – there are no problems connecting.

I am having difficulty with the User Security component when attempting to use Certificates and Private Keys. I’m not familiar with certificates, public and private keys, and Certificate Authorities etc. So I might be completely off the garden path with what I’m attempting to do.

I found the Opc.Ua.CertificateGenerator.exe tool on the OPC UA server. In command prompt, I used the following parameters.

Opc.Ua.CertificateGenerator.exe -cmd issue -sp . -an OPCTEST-o MyCompany –pw password –pem true,

This generated the type of files that seemed to be recognised on the Prosys OPC UA Client (.der for the certificate and .pem for the private key). However, when using the password, the Prosys client produced an error when trying to read the private key:

“Could not load private key: unable to process key spec: java.lang.ClassCastException: org.bouncycastle.asn1.DLSequence cannot be cast to org.bouncycastle.asn1.ASN1Integer”

What am I doing wrong here?