Understanding Key Versions
Though not necessary for most modern users of PGP, understanding PGP key versions can enlighten other questions. There are two key versions which are relevant: PGP Version 3 (V3) and PGP Version 4 (V4). V4 keys were introduced by NAI’s PGP 5.0, which the OpenPGP standard is based on. The standard refers to V3 keys as “old format” and V4 keys as “new format.”
New format keys offer many advantages over old format keys. This includes the inclusion of many different subpackets that can be attached to a public key, sort of addendums to the key, which can specify information such as prefered hash algorithm, preferred key server, or revocation information. As GnuPG and PGP versions since at least 2000 have used new format keys by default, there is little concern here about which key format to use. However, some outstanding keys predate the OpenPGP standard and are still in use today. These keys are acceptable for use provided the owner accepts the key as their own.
