Tails -> Verify the ISO image -> Using the command line: "gpg: Impossible de v'erifier la signature : No public key"

Question

I follow this Tails docs:

$ brew install gpg    

$ gpg --keyid-format 0xlong --verify tails-amd64-3.0.iso.sig tails-amd64-3.0.iso
gpg: Signature faite le Sat Jun 10 17:37:05 2017 CEST
gpg:                avec la clef RSA A5091F72C746BA6B163D1C183C83DCB52F699C56
gpg: Impossible de v'erifier la signature : No public key

$ gpg --keyserver hkp://keys.gnupg.net --keyid-format 0xlong --verify tails-amd64-3.0.iso.sig tails-amd64-3.0.iso
gpg: Signature faite le Sat Jun 10 17:37:05 2017 CEST
gpg:                avec la clef RSA A5091F72C746BA6B163D1C183C83DCB52F699C56
gpg: Impossible de v'erifier la signature : No public key

$ pwd
/Users/fyodor/Downloads/tails-amd64-3.0

Do I miss something or docs not complete?

Answer 1

Two things:

1. This isn't the correct installation method for you to follow.

   These instructions are for people who are already familiar with basic usage of OpenPGP

2. You're not following the instructions at all.

   3. If you are doing the verification for the first time, download the Tails signing key and import it in your keyring. If you are working from Tails, the signing key is already included.

Answer 2

You can also get the "No public key" error if you have imported an old version of the Tails signing key.

gpg --check-sigs A490D0F4D311A4153E2BB7CADBB802B258ACD84F

pub   4096R/58ACD84F 2015-01-18 [expired: 2017-01-11]
uid       [ expired] Tails developers (offline long-term identity key) <tails@boum.org>
sig!3        58ACD84F 2015-01-18  Tails developers (offline long-term identity key) <tails@boum.org>
sig!         BE2CD9C1 2015-01-19  Tails developers (signing key) <tails@boum.org>
sig!3        58ACD84F 2015-09-27  Tails developers (offline long-term identity key) <tails@boum.org>
uid       [ expired] Tails developers <tails@boum.org>
sig!3        58ACD84F 2015-09-27  Tails developers (offline long-term identity key) <tails@boum.org>

The Tails signing key I imported last time expired on 2017-01-11.

After I downloaded the new signing key the result is different:

gpg --check-sigs A490D0F4D311A4153E2BB7CADBB802B258ACD84F

pub   4096R/58ACD84F 2015-01-18 [expires: 2018-01-11]
uid       [ unknown] Tails developers (offline long-term identity key) <tails@boum.org>
sig!3        58ACD84F 2015-01-18  Tails developers (offline long-term identity key) <tails@boum.org>
sig!         BE2CD9C1 2015-01-19  Tails developers (signing key) <tails@boum.org>
sig!3        58ACD84F 2015-09-27  Tails developers (offline long-term identity key) <tails@boum.org>
sig!3        58ACD84F 2016-08-30  Tails developers (offline long-term identity key) <tails@boum.org>
uid       [ unknown] Tails developers <tails@boum.org>
sig!3        58ACD84F 2015-09-27  Tails developers (offline long-term identity key) <tails@boum.org>
sig!3        58ACD84F 2016-08-30  Tails developers (offline long-term identity key) <tails@boum.org>
sub   4096R/752A3DB6 2015-01-18 [expires: 2018-01-11]
sig!         58ACD84F 2015-09-27  Tails developers (offline long-term identity key) <tails@boum.org>
sig!         58ACD84F 2016-08-30  Tails developers (offline long-term identity key) <tails@boum.org>
sub   4096R/2F699C56 2015-01-18 [expires: 2018-01-11]
sig!         58ACD84F 2015-09-27  Tails developers (offline long-term identity key) <tails@boum.org>
sig!         58ACD84F 2016-08-30  Tails developers (offline long-term identity key) <tails@boum.org>
sub   4096R/A0EDAA41 2016-08-30 [expires: 2018-01-11]
sig!         58ACD84F 2016-08-30  Tails developers (offline long-term identity key) <tails@boum.org>

The new key expires in 2018-01-11. Now when I verify the signature I see "Good signature".