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I was looking at GnuPG manual (Manual) and came across below section at page 18:

chloe% gpg -edit-key chloe@cyb.org

Secret key is available.

pub 1024D/26B6AAE1 created: 1999-06-15 expires: never trust: -/u

sub 2048g/0CF8CB7A created: 1999-06-15 expires: never

sub 1792G/08224617 created: 1999-06-15 expires: 2002-06-14

sub 960D/B1F423E7 created: 1999-06-15 expires: 2002-06-14

(1) Chloe (Jester) <chloe@cyb.org>

(2) Chloe (Plebian) <chloe@tel.net>

It says: The keyword pub identifies the public master signing key, and the keyword sub identifies a public subordinate key.

I am not understanding, what is subordinate key for? Any help?

Vadim Kotov
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Vicky
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1 Answers1

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Short version: keys are tagged and used for different types of functions. For example, the primary key must be a signing key. Subordinate keys allow for additional functions (ie encryption).

Long Version: From the GNUPG site:In a public-key system, each user has a pair of keys consisting of a private key and a public key.... GnuPG uses a somewhat more sophisticated scheme in which a user has a primary keypair and then zero or more additional subordinate keypairs. The primary and subordinate keypairs are bundled to facilitate key management and the bundle can often be considered simply as one keypair.
...
GnuPG is able to create several different types of keypairs, but a primary key must be capable of making signatures. There are therefore only three options. Option 1 actually creates two keypairs. A DSA keypair is the primary keypair usable only for making signatures. An ElGamal subordinate keypair is also created for encryption
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it is possible to later add additional subkeys for encryption and signing.

xelco52
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  • So each primary/subordinate key is actually a key pair consisting of a private key and its corresponding public key, right? I mean, it seems obvious at this point, but sometimes I need to have things explained like to a 5 year old. – toraritte Jul 11 '20 at 18:20
  • That's right, primary and subordinates are keypairs (private and public key). So suppose you have one Primary keypair, and one subordinate keypair, you end up having 4 keys. – flyer88 Oct 09 '20 at 03:06