I wrote a self-defined OpenSSL engine and engine tester in ubuntu 20.4. And the OpenSSL version is 1.1.1. The goal is to use engine in TLS session, and the first step is to use command line to sign a digest. The reference website is: https://wiki.openssl.org/index.php/Creating_an_OpenSSL_Engine_to_use_indigenous_ECDH_ECDSA_and_HASH_Algorithms But the tester use the engine by calling the function, like ECDSA_sign and ECDSA_verify in