> I'd like to ask whether it's possible to have a Canonicalizer remove unused > namespace declarations from input XML files
That's what Exclusive C14N does, modulo the fact that it's practically impossible to actually know when namespaces are in fact used in many common protocols (your example is merely a trivial one that doesn't get into the problematic territory, which is primarily when schemas and xsi:type are involved). In general, you will never end up in a state where signed XML is anything but tremendously brittle, and you shouldn't waste a lot of time trying. But the purpose of Exclusive is to support wrapping scenarios where the signed content is removed from the context and verified in a different or isolated context, but it works no better than "somewhat". -- Scott
