The concept behind this is, that it is said, if one key is compromised, only a part of the
whole "system" is affected. If someone compromises your signing-key hi is still
unable to decrypt your mails.
IPsec for example also has different key material for signing and different key material
for encrypting packets. This is a security engineers philosophy. As far I remember this
was a criticized point of WEP weaknesses, WEP uses the same cryptographic material for
signing and encryption.
I do not think the point behind this is to sell more certificates. If this principle is
used, normally both certificates are issued the same time.
From: users-bounces(a)lists.djigzo.com [mailto:firstname.lastname@example.org] On Behalf Of
Sent: Friday, February 25, 2011 11:49 AM
Subject: Re: [Djigzo users] Strange Key Usage "nonRepudiation"
Zitat von Manuel Faux <Manuel.Faux(a)securesolutions.at>at>:
Not really related, but maybe it will clarify the point:
In Austria for example it is law, that a signed document is equally
trustworthy like a hand-signed document, if the signature was created
by an qualified-certificate (in short, a certificate on a SmartCard,
which was signed by the Austrian government). If I sign a contract
with my SmartCard, the signature itself cannot be disputed by any
The same will maybe happen in germany too. But the question is why the certificates are
limited to signing? Is there any security drawback in allowing encryption? For me it only
looks like the opportunity to sell *two* certificates to the same person.