Certificate Key Size Value Error When Validating SharePoint Online Source

Symptom

When validating a SharePoint Online source, the following error appears:

The certificate used must have a key size of at least 2048 bits.

Cause

The issue occurs when a third-party certificate authority has been used and the generated certificate for Azure app is only 1024 bit.

Resolution

Create a new 2048 bit certificate using your certificate authority tool.

Then import and upload it to to Azure for SharePoint Online app per normal configuration insctructions.

For additional information on how to prepare the certificate for your Azure AD app, refer to the following article: Step 1: Prepare application certificate.