Online Tools
Really nice set of tools to do a bunch of things, https://www.sslshopper.com/ssl-converter.html
Testing
Assuming that your CA certs are available, without a web server you can determine if a certificate is valid,
openssl s_server -cert www.krypton.com_server.crt -key www.kryptong.com_server.key -CApath /etc/ssl/certs/ -www
The result will be an SSL http service listening on port 4433 with the follow response from the running the command,
Using default temp DH parameters Using default temp ECDH parameters ACCEPT
Further testing can be done by pointing your browser to, https://www.krypton.com:4433 where you will a page showing the various ciphers available and some statistics about your connection. Most modern browsers will also allow you to examine the certificate as well.
Getting Information
An SSL certificate contains information about, issuer, valid dates, subject, and crypto. The useful thing about this command is that you do not need CA certificates to view certificates,
openssl x509 -text -in www.krypton.com_server.crt