How STIR/SHAKEN Signs and Verifies Caller ID on IP Phone Networks

STIR/SHAKEN is a caller ID authentication framework for IP-based phone networks, in which the originating carrier attaches a digital signature to the calling number. That signature carries an A, B, or C attestation indicating how much the provider knows about the customer and number. The receiving carrier checks the signature against the actual call data to confirm who vouched for the number. The result only shows that a number was vouched for, not that the caller is honest, and it does not by itself block calls. Coverage remains partial, and signatures can be lost where calls pass through non-IP links or have headers stripped, while some countries such as India use different approaches.