Two commands which you need to run. #openssl rsa -noout -text -in www.domainname.com.key #openssl req -noout -text -in www.domainname.com.csr #openssl x509 -noout -text -in www.domainname.com.crt Check for modulus part in the output of both commands If the modulus output match, then your .crt and .key files are matching.