The PKCS#12 or PFX format is a binary format for storing the server certificate, any intermediate certificates, and the private key into a single encryptable file. PFX files are usually found with the extensions .pfx and .p12. PFX files are typically used on Windows machines to import and export certificates and private keys.

• The original private key used for the certificate
• A PEM (.pem, .crt, .cer) or PKCS#7/P7B (.p7b, .p7c) File
• OpenSSL

The commands below demonstrate examples of how to create a .pfx/.p12 file in the command line using OpenSSL.

openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile more.crt

Breaking down the command:

• openssl – the command for executing OpenSSL
• pkcs12 – the file utility for PKCS#12 files in OpenSSL
• -export -out certificate.pfx – export and save the PFX file as certificate.pfx
• -inkey privateKey.key – use the private key file privateKey.key as the private key to combine with the certificate.
• -in certificate.crt – use certificate.crt as the certificate the private key will be combined with.
• -certfile more.crt – This is optional, this is if you have any additional certificates you would like to include in the PFX file.