openssl x509 -in cert.pem -noout -text -dates -subject
openssl req -new -newkey rsa:2048 -nodes -keyout k.pem -out c.csr -subj "/CN=example.com"
openssl rsa -in k.pem -check
openssl pkcs12 -export -in cert.pem -inkey k.pem -out bundle.p12

openssl s_client -connect h:443 -servername h -showcerts -status </dev/null
openssl s_client -connect h:443 -tls1_3 -brief </dev/null
openssl ciphers -v 'ECDHE+AESGCM:CHACHA20'

openssl dgst -sha256 file
openssl rand -hex 16
openssl speed -evp aes-128-gcm