RE: German Key Usage

[Russ Housley <housley@xxxxxxxxxx>]

No.  Sometimes it is perfectly acceptable to use one key for authentication
and non-repudiation.

I would say that there is agreement that key management and digital
signature should not be mixed.  Yet, we have many deployed protocols that
do just that.

Russ


At 04:14 PM 8/13/98 +0200, lars.gu.johansson@posten.se wrote:
>Key users,
>
>Seems to me that everyone agrees that it is essential
>to separate the two security services authentication and
>non-repudiation by using different keys. That's why I've
>previously supported the idea of never mix these key
>usages (DS and NR) in the same certificate.
>
>However, if the intepretation of the bits, as some of you
>point out, should be that digitalSignature (DS) indicates a
>MECHANISM wheras nonRepudiation (NR) is a SERVICE,
>then indeed can there be a good reason for having both
>bits set.
>
>In order to still achieve the separation of the authantication
>and non-repudiation service, I would propose the addition
>of yet another key usage bit, namely the authentication (A)
>SERVICE bit!
>
>That could make sense: either the keyUsage field of the
>certificate has DS+A set, indicating an authentication
>service based on a digital signature mechanism. Or the
>certificate would have the keyUsage field set to DS+NR,
>indicating a non-repudiation service based on a digital
>signature mechanism.
>
>(Thinking of it: Wouldn't it also be possible to implement an
>authentication service based on an data-encipherment
>mechanism? If so, then the keyUsage would be DE+A)
>
>The drawback of this aproach is that it adds further complexity
>to an already quite complex concept. My only concern is that
>we can agree on ONE solution that everyone interpret the same
>way. Perhaps it's better to stick to the original idea of never
>combining the DS and NR bits? Opinions?
>
>/Lars Johansson
>