Where can I download the latest SAP Ariba certificates?

A list of all current SAP Ariba certificates are available for download on the Public Certificate Downloads page.

A list of certificates that are scheduled to be updated soon can be found on the Public Certificate Repository page under the Next Planned Certificate Update section.

Core Procurement > Core Administration > Application Integration (between Buying & Sourcing)
SAP Integration Suite Managed Gateway > Managed Gateway Foundation & Tools > Managed Gateway Platform