This is an attempt at implementing the OpenOCES API (OOAPI), otherwise only available as .NET and Java libraries, in Ruby.

OOAPI is used to loading and verifying OCES certificates, used in the national Danish infrastructure system NemID. OCES certificates are basically X.509 certificates with a few extra properties.

For a typical log-in setup, the user is presented with a Java applet in a browser as log-in prompt. After a log-in process, the server is presented with some XMLDSig, which OOAPI will then consume and validate.

The Java and .NET versions of OOAPI are available here

It should be extremely easy to support NemID log-in in your Ruby-based web application backend, no matter which web application framework you use.

The idea is not to copy all the functionality from the original OOAPI versions, only the bare necessities. For example:

• The original OOAPI versions support partial revocation lists, full revocation lists, and OCSP responders as ways to check the validity of a certificate. By default, partial revocation lists are used, and most clients will never need anything else. That's all we'll support, then.
• The original OOAPI versions support a lot of queries on OCES certificates. We will only support what is strictly necessary to support login and signing.
• The original OOAPI versions have two API layers, where clients will typically use the most abstract layer (the "security package"). Hence, the functionality in this layer is what we will opt for.
• The original OOAPI versions include a so-called PID client, which can be used to verify that a Danish civil registration number (CPR number) matches a PID or actually get the civil registration number from a PID. (The latter service is only available for public institutions.) We might not support this, since it is not strictly necessary for log-in and signing.

Uh-oh. We're just getting started. Fooling around.