Most Certificate Authorities (CAs) issue certificates in PEM format.
PEM certificates typically have extensions like .pem, .crt, .cer, and .key.
The PEM format uses the header and footer lines -----BEGIN CERTIFICATE----- and -----END CERTIFICATE-----.
Other certificate formats include the DER/Binary, P7B/PKCS#7, and PFX/PKCS#12 formats.
Converting Your Existing Certificate To PEM Format
If your certificate is not in PEM format, you can convert it to the PEM format using the following OpenSSL commands:
openssl x509 -inform der -in certificate.cer -out certificate.pem
openssl pkcs7 -print_certs -in certificate.p7b -out certificate.pem
openssl pkcs12 -in certificate.pfx -out certificate.pem -nodes
If you try to upload a passphrase-protected private key file, you will get a "key is invalid" error message. To fix this you will need to remove the passphrase from your private key file and upload the passphrase-free private key file to your appliance. You can remove the passphrase as follows:
Run openssl rsa -in example.key -out example.nocrypt.key
Enter your passphrase.