[openssl-users] How to prove a Certificate is Signed or not

[Salz, Rich]

>    After the generation of SignedCertificate.pem. I would like to write
    function to verify the SignedCertificate.pem, whether it is signed or not.
  
That is still not an accurate description.  By definition, a certificate is *signed data.*  It appears as a bitstring in the X509 data structure.

Is this want you want to do?  You have a certificate, and a CA key or certificate.  You want to know if the CA's public key generated the signature that is in the certificate that you have.  Look at the X509_verify function.  You will need to take your CA cert (or key) and make a key object, but start with that first manpage and follow the references.