Message-ID: <YuUuQ9shkkY7gco4@bobwxc.mipc>
Date:   Sat, 30 Jul 2022 21:12:35 +0800
From:   Wu XiangCheng <wu.xiangcheng@...ux.dev>
To:     Konstantin Ryabitsev <konstantin@...uxfoundation.org>
Cc:     Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v1 1/5] maintainer-pgp-guide: use key terminology
 consistent with upstream

Hi,

话说 Konstantin Ryabitsev 于 2022-07-28 (四) 16:57:04 -0400 曰过：
> GnuPG does not use the word "master key" when referring to the subkey
> marked with the "certification" capability. Our use of this term was not
> only inconsistent, but also misleading, because in real life "master
> keys" are able to open multiple locks made for different keys, while PGP
> Certify key has no such capability.

They use "primary key" in their interface and document.

For example in their .po file:

msgid "Note: The public primary key and all its subkeys will be deleted.\n"
msgid "using subkey %s instead of primary key %s\n"

Also in gnupg/doc/gpg.texi:

By specifying the key to export using a key ID or a fingerprint
suffixed with an exclamation mark (!), a specific subkey or the
primary key can be exported.  This does not even require that the key
has the authentication capability flag set.

Using the new word?

> 
> Signed-off-by: Konstantin Ryabitsev <konstantin@...uxfoundation.org>
> 
> diff --git a/Documentation/process/maintainer-pgp-guide.rst b/Documentation/process/maintainer-pgp-guide.rst
> index 29e7d7b1cd44..cdd108f50fe7 100644
> --- a/Documentation/process/maintainer-pgp-guide.rst
> +++ b/Documentation/process/maintainer-pgp-guide.rst
[...]
> +
> +Understanding PGP Subkeys
> +-------------------------
> +
> +A PGP key rarely consists of a single keypair -- usually it is a
> +collection of independent subkeys that can be used for different
> +purposes based on their capabilities, assigned at their creation time.
> +PGP defined four capabilities that a key can have:
> +
> +- **[S]** keys can be used for signing
> +- **[E]** keys can be used for encryption
> +- **[A]** keys can be used for authentication
> +- **[C]** keys can be used for certifying other keys
> +
> +The **[C]** (certification) key is often called the "master" key, but

Maybe "The key carrying the **[C]**" is better, match the following
description. As your said, gpg always create a [SC] key by default.

> +this terminology is misleading because it implies that the Certify key
> +can be used in place of any of other subkey on the same chain (like a
> +physical "master key" would). For this reason, this guide will refer to
> +it as "the Certify key" to avoid any ambiguity.
> +
> +It is critical to fully understand the following:
> +
> +1. All subkeys are fully independent from each other. If you lose a
> +   private subkey, it cannot be restored or recreated from any other
> +   private key on your chain.
> +2. With the exception of the Certify key, there can be multiple subkeys
> +   with identical capabilities (e.g. you can have 2 valid encryption
> +   subkeys, 3 valid signing subkeys, but only one valid certification
> +   subkey). All subkeys are fully independent -- a message encrypted to
> +   one **[E]** subkey cannot be decrypted with any other **[E]** subkey
> +   you may also have.
> +3. A single subkey may have multiple capabilities (e.g. your **[C]** key
> +   can also be your **[S]** key).

Reminding the limit of algorithms' capabilities by the way?
Like: As long as under the algorithm's capabilities.

> +
> +The key carrying the **[C]** (certify) capability is the only key that
> +can be used to indicate relationship with other keys. Only the **[C]**
> +key can be used to:
>  
>  - add or revoke other keys (subkeys) with S/E/A capabilities
>  - add, change or revoke identities (uids) associated with the key
> @@ -180,7 +190,7 @@ relationship with other keys. Only the **[C]** key can be used to:
>  
>  By default, GnuPG creates the following when generating new keys:
>  
> -- A master key carrying both Certify and Sign capabilities (**[SC]**)
> +- One subkey carrying both Certify and Sign capabilities (**[SC]**)

I suggest to use "primary key" here. Gnupg use it in their doc, and it is
really shown differently when typing --list-keys.

>  - A separate subkey with the Encryption capability (**[E]**)
>  
>  If you used the default parameters when generating your key, then that
[...]

-- 
Thanks,
Wu XiangCheng 
0x32684A40BCA7AEA7


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