In cryptography, PKCS #12 defines an archive file format for storing many cryptography objects as a single file. It is commonly used to bundle a private key with its X.509 certificate or to bundle all the members of a chain of trust.

A PKCS #12 file may be encrypted and signed. The internal storage containers, called "SafeBags", may also be encrypted and signed. A few SafeBags are predefined to store certificates, private keys and CRLs. Another SafeBag is provided to store any other data at individual implementer's choice.^[2][3]

PKCS #12 is one of the family of standards called Public-Key Cryptography Standards (PKCS) published by RSA Laboratories.

The filename extension for PKCS #12 files is .p12 or .pfx.^[4]

These files can be created, parsed and read out with the OpenSSL pkcs12 command.^[5]

PKCS #12 is the successor to Microsoft's "PFX";^[6] however, the terms "PKCS #12 file" and "PFX file" are sometimes used interchangeably.^[4][5][7]

The PFX format has been criticised for being one of the most complex cryptographic protocols.^[7]

The full PKCS #12 standard is very complex. It enables buckets of complex objects such as PKCS #8 structures, nested deeply. But in practice it is normally used to store just one private key and its associated certificate chain.^{[citation needed]}

PKCS #12 files are usually created using OpenSSL, which only supports a single private key from the command line interface. The Java keytool can be used to create multiple "entries" since Java 8, but that may be incompatible with many other systems.^[8] As of Java 9 (released 2017-09-21), PKCS #12 is the default keystore format.^[9][10]

A simpler, alternative format to PKCS #12 is PEM which just lists the certificates and possibly private keys as Base 64 strings in a text file.

GnuTLS's certtool may also be used to create PKCS #12 files including certificates, keys, and CA certificates via --to-p12. However, beware that for interchangeability with other software, if the sources are in PEM Base64 text, then --outder should also be used.

• RFC 7292 - PKCS #12: Personal Information Exchange Syntax v1.1
• "PKCS #12: Personal Information Exchange Syntax Standard". RSA Laboratories. Archived from the original on 2017-04-17. This standard specifies a portable format for storing or transporting a user's private keys, certificates, miscellaneous secrets, etc.

• Overview about PKCS#12 capabilities, usage, implementations, history and future: Ryan Hurst and Yury Strozhevsky (2015-12-02). "The PKCS#12 standard needs another update". Archived from the original on 2017-03-03.