- From: Phillip M Hallam-Baker <pbaker@verisign.com>
- Date: Wed, 25 Aug 1999 13:04:18 -0400
- To: "Donald E. Eastlake 3rd" <dee3@torque.pothole.com>, "IETF/W3C XML-DSig WG" <w3c-ietf-xmldsig@w3.org>
> >The definition of canonicalization is a function f(x) such that > >f(x) = f(f(x)). > > No. That's the fix point property, which is a desireable property of > canonicalization but by no means its definition. Actually it is a required property for it to be a canonical form. The point of canonicalization is to be able to test for equivalence between different syntactical representations of the same data. > My definition of > canonicalization is a function f(x) which is useful for application A > if f(x1) = f(x2) implies that application A considers x1 and x2 > semantically identical. And f(x1) <> f(x2) implies they are distinct. Therefore a c14n function must have the fixed point property. Lema Exists f(x) <> f(f(x)) for some x => f(x) <> f(x2) where x2 = f(f(x)) but x, x2 are semantically equivalent, therefore f(x) = f(x2), thus disproving the lema. Therefore all canonicalization functions are fixed point functions QED.
Received on Wednesday, 25 August 1999 13:03:56 UTC