openssl X509 reading signature Hash algorithm using C unix
I'm trying to convert my root certificate to Pem files using C unix. In my
current code I'm using the openssl function
const EVP_MD *digest=EVP_sha1();
to make the digest as SHA1, but now I want to modify the code to support
sha256 and sha512.
From the current openssl.h I found that X509->signature gives Signature
Algorithm what my root certificate is holding. But is there a way to find
what is the Signature Hash Algorithm that my root certificate is holding?
Found a similar one in C#: How to retrieve the Signature hash algorithm
friendly name using c# cryptography? But I need a similar one in C.
Also is there any ppt which talks about the unix openssl.h in detail?