CDR: Re: Non-Repudiation in the Digital Environment (was Re: First Monday August 2000)

[Arnold G. Reinhold]

At 12:12 PM -0700 10/7/2000, Ed Gerck wrote:
>"Arnold G. Reinhold" wrote:
>
>> In public-key cryptography "Non-Repudiation" means that that the
>> probability that a particular result could have been produced without
>> access to the secret key is vanishingly small, subject to the
>> assumption that the underlying public-key problem is difficult.  If
>> that property had be called "the key binding property" or "condition
>> Z," or some other matheze name, we would all be able to look at this
>> notion more objectively. "Non-repudiation," has too  powerful a
>> association with the real world.
>
>Your definition is not standard. The Cryptography Handbook by Menezes
>defines non-repudiation as a service that prevents the denial of an act.  The
>same is the current definition in PKIX, as well as in X.509.  This 
>does not mean, however as some may suppose, that the act cannot be 
>denied -- for example,
>it can be denied by a counter authentication that presents an accepted proof.
>
>Thus, non-repudiation is not a stronger authentication --  neither a 
>long lived
>authentication.  Authentication is an assertion that something is true. Non-
>repudiation is a negation that something is false. Neither are absolute.  And
>they are quite different when non-boolean variables (ie, real-world variables)
>are used. They are complementary concepts and *both* need to be used or
>we lose expressive power in protocols, contracts, etc..
>
>Cheers,
>
>Ed Gerck

You may well be right about the accepted definition of 
non-repudiation, but if you are then I would amend my remarks to say 
that known cryptographic technology cannot provide non-repudiation 
service unless we are willing to create a new legal duty for 
individuals and corporations to protect their secret key or accept 
what ever consequences ensue.  I don't think that is acceptable.

I find the rest of your comment a tad too opaque.  Could you give 
some examples of what you have in mind?


Arnold Reinhold