File extension

.gpg

OpenPGP binary data (GnuPG)

.gpg files are binary OpenPGP data produced by GnuPG: encrypted files, signatures, or exported keys, depending on the content (also seen as .pgp).

Known meanings

Formats and reference material for .gpg

OpenPGP binary data (GnuPG)

Binary OpenPGP packets: encrypted data, signatures, or keys, as created by GnuPG

  • data-format misc
  • IETF OpenPGP Working Group / GnuPG Project
Open link

Details

Format notes

GPG (OpenPGP binary data)

A .gpg file is data in the OpenPGP format written by GnuPG (GNU Privacy Guard), the most common implementation of the standard. The extension is used by the gpg tool for encrypted files (gpg --encrypt or --symmetric), for detached or combined signatures, and for exported keys and keyrings. The extension does not tell which of these it is. .pgp is used by other implementations, and .asc stands for the same data in a text encoding.

Structure

OpenPGP, standardized in RFC 4880 and revised by RFC 9580, represents everything as a sequence of packets: public-key and secret-key packets, user IDs, signatures, and encrypted data packets, each with a tag and a length. Encrypted files typically hold one or more session-key packets, which wrap a random key for each recipient’s public key or a passphrase, followed by symmetrically encrypted data. Signatures can be embedded or stored in a separate file.

Tooling

GnuPG (gpg --list-packets shows the packet structure), Gpg4win, GPG Suite, Sequoia-PGP, and many mail clients and package managers handle OpenPGP. GnuPG 2.1 and later store secret keys in a private-keys directory rather than a single keyring file.

Preservation And Security Notes

Decrypting an old file needs the private key and its passphrase, so these must be preserved separately and securely, or the data is permanently lost. Older files may use algorithms now considered weak. Exported secret keys should be kept as protected as passwords.

Further Reading

  • RFC 9580, OpenPGP: https://www.rfc-editor.org/rfc/rfc9580
  • RFC 4880, OpenPGP Message Format: https://www.rfc-editor.org/rfc/rfc4880
  • GnuPG documentation: https://gnupg.org/documentation/