PKCS#12 is the cryptographic standard for packaging a certificate together with its matching private key in a single file, encrypted with a password. On Apple platforms the file usually has a .p12 extension; on Windows the same format is called .pfx. It is how teams share or back up an Apple Developer signing identity.
What is inside
- The leaf certificate (Apple Development, Apple Distribution, Developer ID, etc.).
- The private key that pairs with the certificate's public key.
- Optionally, intermediate certificates (the WWDR generation that signed the leaf).
- An encryption envelope keyed off the password you set at export time.
Two ways to produce one
- Keychain Access
- Right-click the certificate, choose Export, pick `.p12`, set a password. Works only on the Mac where the private key lives.
- openssl
- `openssl pkcs12 -export -out cert.p12 -inkey key.pem -in cert.pem` bundles a certificate and key from PEM files. Useful when the key was generated outside Keychain.