From the Soylent News footnote 6: https://transnexus.com/whitepapers/stir ... -overview/
That has a brief explanation and links to this whitepaper:
https://transnexus.com/whitepapers/unde ... ir-shaken/
STIR and SHAKEN use digital certificates, based on common public key cryptography techniques, to ensure the calling number of a telephone call is secure. In simple terms, each telephone service provider obtains their digital certificate from a certificate authority who is trusted by other telephone service providers. The certificate technology enables the called party to verify that the calling number is accurate and has not been spoofed. The details of how SHAKEN uses public key infrastructure, and the SHAKEN certificate governance model, will be described in future TransNexus blogs and newsletters.
It sounds like the spam callers would have to cooperate to make it work (sigh).