Use Openssl to do signing and verification
 

I used EVP_ functions as shown in demos/sign of OpenSSL to do signing and verification. It works well.The algorithm I chose was SHA-1+RSA. But I want to know how to use ECDSA(Eliptic Curve DSA)+SHA1 algorithm to do signing and verification?

EVP_* use EVP_SignInit to initialize signing, as following:
EVP_SignInit (&md_ctx, EVP_sha1());
But EVP_sha1() will return RSA by default? So how can I use ECDSA instead?

Thanks.