EVP_DigestSignInit ECDSA P-256 SHA-256

[Angus Robertson - Magenta Systems Ltd]

> I am implementing a JWS based specification using openSSL. My 
> code is  below, in pascal. I'm trying to reproduce this test case
> here: https://datatracker.ietf.org/doc/html/rfc7515#appendix-A.3.1
> 
> I get a different outcome from EVP_DigestSignInit / 
> EVP_DigestUpdate /

You could compare your result with our Delphi JWS implementation: 

https://svn.overbyte.be/svn/ics/trunk/Source/OverbyteIcsSslJose.pas

there is an sample app that exercises all the functions.  

Beware the code is changing shortly since all the RSA_ and EC_
functions are deprecated in OpenSSL 3.0.  

Angus