Non-repudiation (was RE: The PAIN mnemonic)

[Ben Laurie]

Amir Herzberg wrote:

> At 04:20 25/12/2003, Carl Ellison wrote:
> ...
> 
>>         If you want to use cryptography for e-commerce, then IMHO you 
>> need a
>> contract signed on paper, enforced by normal contract law, in which one
>> party lists the hash of his public key (or the whole public key) and says
>> that s/he accepts liability for any digitally signed statement that 
>> can be
>> verified with that public key.
> 
> 
> Of course! I fully agree; in fact the first phase in the `trusted 
> delivery layer` protocols I'm working on is exactly that - ensuring that 
> the parties (using some external method) agreed on the keys and the 
> resulting liability. But when I define the specifications, I use 
> `non-repudiation` terms for some of the requirements. For example, the 
> intuitive phrasing of the Non-Repudiation of Origin (NRO) requirement 
> is: if any party outputs an evidence evid s.t. valid(agreement, evid, 
> sender, dest, message, time-interval, NRO), then either the sender is 
> corrupted or sender originated message to the destination dest during 
> the indicated time-interval. Notice of course that sender here is an 
> entity in the protocol, not the human being `behind` it. Also notice 
> this is only intuitive description, not the formal specifications.

What you have here is evidence of origin, not non-repudiation.

Cheers,

Ben.

-- 
http://www.apache-ssl.org/ben.html       http://www.thebunker.net/

"There is no limit to what a man can do or how far he can go if he
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