Non-repudiation (was RE: The PAIN mnemonic)

[Ian Grigg]

Carl Ellison wrote:

> > >From where I sit, it is better to term these
> > as "legal non-repudiability" or "cryptographic
> > non-repudiability" so as to reduce confusion.
> 
> To me, "repudiation" is the action only of a human being (not of a key) and
> therefore there is no such thing as "cryptographic non-repudiability".


Ah.  Now I understand.  The verb is wrong, as it
necessarily implies the act of the human who is
accused of the act.  (And, thus, my claim that it
is possible, was also wrong.)

Whereas the cryptographic property implies no such
thing, and a cryptographic actor can only affirm
or not, not repudiate.  I.e., it's a meaningless
term.


> We
> need a different, more precise term for that -


Would "irrefutable" be a better term?  Or non-
refutability, if one desires to preserve the N?

The advantage of this verb is that it has no
actor involved, and evidence can be refuted on
its own merits, as it were.

As a test, if one were to replace repudiate
with refute in the ISO definition, would it
then stand?


> and we need to rid our
> literature and conversation of any reference to the former - except to
> strongly discredit it if/when it ever appears again.

I think more is needed.  A better definition is
required, as absence is too easy to ignore.  People
and courts will use what they have available, so it
is necessary to do more; indeed it is necessary to
actively replace that term with another.

Generally, the way the legal people work is to
create simple "tests".  Such as:

  A Document was signed by a private key if:

  1. The signature is verifiable by the public key,
  2. the public key is paired with the private key,
  3. the signature is over a cryptographically strong
     message digest,
  4. the Message Digest was over the Document.

Now, this would lead to a definition of irrefutable
evidence.  How such evidence would be used would be
of course dependent on the circumstances;  it then
becomes a further challenge to tie a human's action
to that act / event.



iang


PS: Doing a bit of googling, I found the ISO definition
to be something like:

http://lists.w3.org/Archives/Public/w3c-ietf-xmldsig/1999OctDec/0149.html
>> >... The ISO
>> >10181-4 document (called non repudiation Framework) starts with:
>> >"The goal of the non-repudiation service is to collect, maintain,
>> >make available and validate irrefutable evidence concerning a
>> >claimed event or action in order to solve disputes about the
>> >occurrence of the event or action".

But, the actual standard costs money (!?) so it is
not surprising that it is the subject of much
controversy :)

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