Install the OpenSSL on Debian based systems
sudo apt-get install openssl
Create a private key
openssl genrsa -out server.key 4096
Generate a new private key and certificate signing request
openssl req -out server.csr -new -newkey rsa:4096 -nodes -keyout server.key
Generate a self-signed certificate
openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:4096 -keyout server.key -out server.crt
Generate a certificate signing request (CSR) for an existing private key
openssl req -out server.csr -key server.key -new
Generate a certificate signing request based on an existing certificate
openssl x509 -x509toreq -in server.crt -out server.csr -signkey server.key
Remove a passphrase from a private key
openssl rsa -in server.pem -out newserver.pem
Parse a list of revoked serial numbers
openssl crl -inform DER -text -noout -in list.crl
Check a certificate signing request (CSR)
openssl req -text -noout -verify -in server.csr
Check a private key
openssl rsa -in server.key -check
Check a public key
openssl rsa -inform PEM -pubin -in pub.key -text -noout
openssl pkey -inform PEM -pubin -in pub.key -text -noout
Check a certificate
openssl x509 -in server.crt -text -noout
openssl x509 -in server.cer -text -noout
Check a PKCS#12 file (.pfx or .p12)
openssl pkcs12 -info -in server.p12
Verify a private key matches an certificate
openssl x509 -noout -modulus -in server.crt | openssl md5
openssl rsa -noout -modulus -in server.key | openssl md5
openssl req -noout -modulus -in server.csr | openssl md5
Display all certificates including intermediates
openssl s_client -connect www.paypal.com:443
Convert a DER file (.crt .cer .der) to PEM
openssl x509 -inform der -in server.cer -out server.pem
Convert a PEM file to DER
openssl x509 -outform der -in server.pem -out server.der
Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM
openssl pkcs12 -in server.pfx -out server.pem -nodes
Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)
openssl pkcs12 -export -out server.pfx -inkey server.key -in server.crt -certfile CACert.crt