Is it "GPG" or "PGP"?
The Pretty Good Privacy (PGP) suite is a collection of non-free programs originally written by Phil
Zimmerman in 1991, now developed by Broadcom. When writing PGP, Zimmerman requested for comments (RFC 1991) on the format(s) used by the
PGP suite. In two further iterations, RFC 4880 was born, defining the OpenPGP message format. This (free, open) standard is
implemented by the free GNU Privacy Guard (GnuPG
or GPG). The main executable belonging to the GnuPG package in most Linux distributions is called
gpg.
So, really my “key” is a public key that I created using
the gpg utility, conforming to the OpenPGP standard which in turn was derived from the PGP
implementation; this OpenPGP key is essentially a bundle of (public) keys used for encrypting to me, and
verifying my signatures. Calling gpg -k ryan@rueg.re will show the subkeys each with a different
role (encrypting, signing, authenticating in my case).
pub ed25519 2024-08-14 [SCA] [expires: 2027-08-14]
C1E5054517019900672EE0062F91A80A59496DC6
uid [ unknown] Ryan Rueger <ryan@rueg.re>
sub cv25519 2024-08-14 [E] [expires: 2029-08-13]
sub ed25519 2024-08-14 [S] [expires: 2029-08-13]
sub ed25519 2024-08-14 [A] [expires: 2029-08-13]
We can also see that these keys use different algorithms based on Bernstein’s Curve25519, which
was the future-default when I created my key.
This story gives us the different reasonable nomenclatures: the key is technically an OpenPGP key, but this is
often shortened to a “PGP key”. Since many people, however, interact with their “PGP” keys using the tool
gpg, they may also call these “GPG” keys.
Last time I checked, the Google Ngram for “PGP key” vs “GPG key” (case insensitive) had “GPG key” being more popular than “PGP key”.