There are simple tools available to convert a JKS private key into pkcs8
format
which, together with the exported certificate can be transformed into pkcs12

Just google : 'keytool openssl conversion'

Daniel Stenberg wrote:

> On Fri, 2 Sep 2005, rajagopal.varadharajan_at_bt.com wrote:
>
>> How do I use the JKS with curl instead of the using --cacert and
>> --cert and --key?
>
>
> I have no idea what a JKS is, but I figure it is a way to provide a
> certificate? Is it a crypto "engine" ? If so, then --engine is
> possibly what you're looking for.
>

-- 
To verify the signature, see http://edelpki.edelweb.fr/ 
Cela vous permet de charger le certificat de l'autorité; 
die Liste mit zurückgerufenen Zertifikaten finden Sie da auch.