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In reply to Jose Simoes's message sent 2006-10-24 05:05:
> Thanks for the answers about sub-keys
>
> Questions I would like to find in a sub-keys FAQ. I miss the
> answers 
(
> (a) sub-keys are created in pars (private+public) or just one key at
> a time.
Pub/pvt pairs. It makes no sense to have one without the other, else the
one has no purpose (only a pvt key can decrypt that encrypted to the
matching pub key, and only a pub key can be used to verify a sig issued
by the matching pvt key).
> (b) can any sub-key be used to encrypt AND to sign documents?
A key (subkey) can be flagged for either or both purposes. Keep in mind
that the type of key must be appropriate to the intended purpose (ie,
you can't sign with an encryption only subkey (ie, Elg-E (DH)).
> (c) Can sub-keys share the same password / phrase with the main key
> and other sub-keys ?
All keys are arranged in a package, and the package is encrypted with a
single passphrase. It's not trivial to arrange things so that each
subkey has a different passphrase. This can be done, as it is on my
system so that message signing can be performed with a different
passphrase then data signing, but this entails that I keep multiple
keyrings with different copies of my key containing different subkeys
and encrypted with a different passhrase on each separate keyring.
> (d) If I have a valid (main) public + private encrypted key +
> appropriate password can I generate any number of sub-keys with any
> time limit and anytime I want?
Yes.
> (e) Someone with 2 different of my (public?) sub-keys and its
> fingerprints has a good change of find out the are sub-keys of the
> same key?
The subkeys are part of an entire key package known by the keyid (and
fingerprint) of the master signing key (primary key). It's not just a
good chance. It's definite. Take this mesage, for example. It is signed
with a subkey. Your verification output should inform you of the
fingerprint of the subkey used to sign the message, and the fingerprint
of the main key to which the subkey belongs.
> (f) Can I use a expired sub-key (knowing the encrypted sub-key and
> the password) to decrypt or check the signature of a document -
> probably encrypted or signed long ago when when the key was valid ?
Yes.
> (g) If some one signs my main key is it necessary to signed any sub-
> key (more: and if the sub-key was created after the signature?) .
Only the primary key is signed.
You sign your own keys (self-signing) to indicate that all the keys in
your package are your authentic keys. Self-signing is part of the key
generation process. Others sign only your primary key because that's the
only key you can use to issue signatures to authenticate other UID's or
subkeys. Others sign the key that's used to sign keys. It's a path that
can be followed. There is no need for someone to sign a subkey because
they can sign the key that signed the subkey.
> (h) Can I create a revocation certificate for a sub-key if I lost
> the sub-key (but still have everything about the main key).
The most recently generated subkey is used by default, so it's no big
deal if you are unable to revoke a subkey. Just replace it by generating
a new subkey.
- --
List Moderator, PGP Encryption Help Team
Mike Daigle http://www.mikedaigle.ca
My PGP Key Send email with subject=pgpkey-request
Gossamer Spider Web of Trust http://www.gswot.org
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sixdemonba