Re: SV: Defining Non-Repudiation

All,

I agree with the gist of what most of you have stated.  In general terms,
we all know that the CA is responsible for catching attempts at fraudulent
certificate subscription.  Neither the relying party, nor the impersonated
victim can assist in this prevention.

We also know that the use to which a private key is put is under the control
of the key-holder (subscriber).  Unless I am mistaken, it is also the
subscriber who has (marginal) control of the "signing software".  I also
believe that most signing software does not demand the presence of a valid
certificate in _applying_ the key (please correct me if I am wrong).

Also, the "enduring signature" (allowing validation after cert expiration)
certainly required some archiving of certs and/or CRLs by someone...

Finally, it is the relying party that controls the "validation software",
which does (can) demand appropriate certificates be present to successfully
process a signed transaction.

Given all of this, the intent of the "NR" bit should be described in terms
of what (pkix-compliant) software is forced to rely upon it, and with what
implications.  Otherwise it seems to be nothing more than an advisory, or
at most, a promise of greater "due diligence" from the CA in exchange for
a bigger pile of coins.

I update the scenarios I gave previously, for thought:

1.  Claim Fraudulent Subscription.

    As a criminal, I take the effort to impersonate you so well (false IDs)
    that I get a CA to issue a "NR" cert to me in your name, etc.  Granted
    the CA followed their CPS to the letter, but were still fooled.

    In this case, what does the NR bit do for anyone (except the criminal.)

2.  Claim Flawed Validity:

    A (possibly expired) key is used to sign a transaction where the signing
    date is abused.  The criminal "backdates" the signature.  Is this even
    an NR-case at all?  Here, it seems it is the relying party that will
    want to repudiate the validity.

3.  Claim Covert Compromise:

    Despite your best efforts, someone stole your key (or so you claim).
    Where, if at all, does the NR-bit affect this situation?

I hope I am not coming across as obstructionist.  I simply do not understand
what the NR-bit is saying, and to whom it is speaking.  Enlightenment welcome!

___tony___

Tony Bartoletti                                             LL
SPI-NET GURU                                             LL LL
Computer Security Technology Center                   LL LL LL
Lawrence Livermore National Lab                       LL LL LL
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