Token RSA public key from modulus

I do get the jwks keys using the URL https://{{oktadomain.com}}/api/v1/oauth2/{{authserverid}}/v1/keys but the key modulus is in some encoded format. I have 2 questions.

  1. What format it is encoded in? How do I decode it. I could not do base64 decode for the modulus.
  2. My client application is in C++. Is there any C++ reference code to build the RSA key suitable for signature verification using the modulus there?

I think it’s described here - rfc7518 for “n” and “e” parameters of a key.

If you go to https://jwt.io and scroll a bit, there will be a list of libraries supporting JWT verification. Might be some of them have classes for building a JWK from “n” and “e”