What are STIR and SHAKEN and how do they work together?

STIR stands for Secure Telephone Identity Revisited — it is an IETF standard that defines how to digitally sign a call's originating identity using cryptographic certificates. SHAKEN stands for Signature-based Handling of Asserted information using toKENs — it is the implementation framework that governs how those signatures are applied by telephone service providers in practice. Together, STIR/SHAKEN creates a verifiable chain of trust from the originating carrier to the terminating network: when a signed call arrives, the receiving carrier can verify that the Caller ID was authenticated at source and has not been tampered with in transit.