[LINK] Does High Court GetUp result clarify e-witnessing? [was: High Court case Re: Register Online to Vote Should be Legal]

Roger Clarke Roger.Clarke at xamax.com.au
Mon Aug 23 11:00:25 AEST 2010

At 10:31 +1000 23/8/10, Tom Worthington wrote:
>Presumably "signatures" are used to:
>1. Identify a person,

Nope.  That's a *common* mis-use of the word 'identify', but it's 
important that we use language carefully.

The process of identification involves someone asserting that they 
are appropriately associated with some identifier, e.g.
'I'm <uncommon name>'
'he's <common name> whose birthdate is <date>'
'she's the person who was assigned <id-code> by <organisation-name>'
'that's the particular Mohammad Yusuf who is a suspected terrorist 
and isn't allowed on aircraft'.

A signature may be used to **authenticate** an identity assertion.

I *think* the convention is that 'if the person can produce a 
signature that has a superficial resemblance to one I already have 
available to me from some other reliable source, then I will 
reasonably feel more confident that they really have a claim to that 

The reason we're all pretty sus about signatures as authenticators is 
that there are a great many flaws in the logic, e.g. there may not be 
a reference-copy to compare the new signature with, the source of the 
reference-copy may be tainted, a signature is not a secret and hence 
is wide open to spoofing.

>2. Link a person to a document,

Yes to that one, where the document contains a signature.

That's a use as an authenticator of a different assertion, such as 
'this is the same as the person who signed that document'.

>3. Give the person the sense that what they are "signing" is important
>and so they need to make a full and truthful statement.

And yes to that one.


Roger Clarke                                 http://www.rogerclarke.com/

Xamax Consultancy Pty Ltd      78 Sidaway St, Chapman ACT 2611 AUSTRALIA
                    Tel: +61 2 6288 1472, and 6288 6916
mailto:Roger.Clarke at xamax.com.au                http://www.xamax.com.au/

Visiting Professor in the Cyberspace Law & Policy Centre      Uni of NSW
Visiting Professor in Computer Science    Australian National University

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