Most efficient way to look whether a secret key is for X.509 or for OpenPGP

[Rainer Perske]

Hello,

I use gpgsm and gpg2 concurrently. I can quickly and easily see whether
there are private keys in gnupghome/private-keys-v1.d/. But I cannot
easily see whether these keys belong to X.509 key pairs or to OpenPGP
key pairs.

For my application, I need to know:

a) What is the fastest way to detect whether I have a private X.509
   key? I need a simple boolean answer: yes or no.

   The response time of » gpgsm --list-secret-key « is .4 seconds, that
   is far too long.

b) What is the fastest way to detect whether I have a private OpenPGP
   key? I need a simple boolean answer: yes or no.

   The response time of » gpg2 --list-secret-key « is .4 seconds, that
   is far too long.

c) What is the fastest way to detect whether a private key in
   gnupghome/private-keys-v1.d/ belongs to an X.509 key and/or to an 
   OpenPGP key? I need a simple answer: X.509-only, OpenPGP-only or 
   both.

   The response time of » gpgsm --list-secret-key '&'${filename%.key} «
   and » gpg2 --with-keygrip --list-secret-key | grep ${filename%.key}
   « is 1 second, that is far too long

(My application needs these responses very quickly without any visible
delay. There is no time to wait for startup of gpg-agent, dirmngr or
any other daemon first. Perhaps there is already any indicator in the 
.key file?)

Best regards
-- 
Rainer Perske
Abteilung Systembetrieb und Leiter der Zertifizierungsstelle (WWUCA)
Zentrum für Informationsverarbeitung (Universitätsrechenzentrum)

Westfälische Wilhelms-Universität
Zentrum für Informationsverarbeitung
Rainer Perske
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48149 Münster

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