Encoding using SHA256 with RSA

Question

I'm attempting to authorize with the Google Data API as a service in a language for which there isn't any client library. The crux is in how to generate the signature. To do this I have to encode a string using "SHA256 with RSA".

I have it from here that it shouldn't be "terribly difficult" however I cannot find a description of the procedure? Anyone knows?

(The language does have a function to generate SHA256 hash codes.)

Answer 1

OAuth 2.0 requires RSASSA-PKCS1-V1_5-SIGN, which is described in RFC 3447. Just check section 9.2 of this RFC - you need just add some formatting to the hash of your message.