RE: pre-shared key v RSA encryption or RSA signature authentication modes

["Rajesh Mohan" <rajesh.mohan@nexsi.com>]

bits of entropy at the highest, and probably much lower than that.
>
> Based on the lack of entropy in shared secrets, I believe RSA sigs
> to be much stronger due to the better entropy in the key.
>

Centrally managed boxes typically get their shared secret from a management
station which is generated using RNG. So, entropy of those keys are as good
as RSA sigs.

And typically, centrally managed boxes send these keys through some
encrypted channel (eg SSL) to these boxes which may make it look bad.











> -derek
>
> Uri Blumenthal <uri@lucent.com> writes:
>
> > "Prof. Ahmed A. A. Adas" wrote:
> > > As a researcher in cryptosystems and protocols, I would say
> that RSA-sig IKE
> > > is much more powerful unless someone is using quantum
> computing attacks,
> > > which are not feasible in the near future.
> >
> > It is comparing apples with oranges.  The conclusion appears
> > incorrect,
> > and way too generalizing [without due justification].
> >
> > Please explain - based on what is, say 2048-bit RSA-sig stronger than,
> > say 256-bit key-based AES-XCBC-MAC signature? What is your criteria?
> > What attacks are you considering? What is your model?
> > --
> > Regards,
> > Uri
> > -=-=-=<>=-=-
> > <Disclaimer>
>
> --
>        Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
>        Member, MIT Student Information Processing Board  (SIPB)
>        URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
>        warlord@MIT.EDU                        PGP key available