There really is no way of doing what you’re thinking about. STIR/SHAKEN is really for calls TO US/Canada numbers. Where all incoming calls should have an Identity header which you can then validate. Even incoming international calls should in theory include said header as a transit (attestation C) source.

You are receiving calls from US/Canada numbers to non-US/Canada numbers.

You could, on the other hand, require your inbound providers to forward the identity header and you could then validate it, and act accordingly. Whether the providers will do that is another story.



On Thu, 22 Jul 2021 at 16:52, Oleg Belousov <obelousov@gmail.com> wrote:
STIR-SHAKEN is currently only applicable for the US and Canada. To be part of it service provider must have an Operating Company Number (OCN) which allows access to NANPA Numbering Resource assignments. That also means (and as per my knowledge/experience) - US/Canadian SPs only sign calls with +1 destination. It is however worth it to check if the identity header is present in calls you receive. If it is here - then you can validate MT calls even not being part of a stir-shaken ecosystem.


On Thu, Jul 22, 2021 at 4:31 PM Benoît Panizzon <benoit.panizzon@imp.ch> wrote:
Hi

> You need first to register with STI-PA (Policy Administrator), in
> order to receive a token to obtain further certificates from an
> approved Certification Authority.
> In the US STI-PA is Iconectiv, in Canada - Neustar. Please check that
> link https://authenticate.iconectiv.com/

Thank you for that link. This is very interesting.

We receive an increasing number of calls from spoofed US numbers in
Switzerland. Mostly tech support scams. I was pondering if there is a
way to validate them via STIR/SHAKEN.

We try to filter out invalid +1 prefixes and lengths, but that is a
rather fuzzy thing to do.

So it would be great, if we could implement STIR/SHAKEN to validate
received calls from the +1 prefix.

Unfortunately to register for a STI-PA account, only TSP with an
address in he United States are allowed. Do you know if there is a way
to register as a Swiss Ofcom registered TSP?

(And yes, I am aware that signature signalling also has to be
implemented but we have to start somewhere).

Hopefully STIR/SHAKEN can in future be deployed on a global level.
Germany and UK would also benefit a lot, seeing also a lot of spoofed
calls with their prefixes.

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