Spam and robocalls have become an increasingly significant problem in the US, leading to consumers losing trust in businesses. STIR/SHAKEN is a set of protocols designed for businesses to gain back this trust by authenticating the businesses making calls and the caller ID used in them.
STIR/SHAKEN stands for the Secure Telephone Identity Revisited (STIR) and Signature-based Handling of Asserted Information Using toKENs (SHAKEN). Under STIR/SHAKEN, every voice call in the US is assigned an attestation — a stamp of legitimacy provided by the originating service provider, authenticating that the call originated from its network. Calls are then passed to the terminating service provider for verification. There are three levels of call attestations:
Full attestation (A) — The service provider has authenticated its relationship with the customer making the call and the customer is authorized to use the calling number.
Partial attestation (B) — The service provider has authenticated its relationship with the customer making the call, but cannot verify that the customer is authorized to use the calling number.
Gateway attestation (C) — The service provider has authenticated that it has placed the call on its network, but has no relationship with the originator of the call (for example, a call received from an international gateway).
For both outbound and inbound calls, Shape can identify the verification status of a call as a parameter called STIR Verification, which can have one of three values:
Verified means the call is from a Verified caller who has authorized access to the customer’s caller ID, and hence should be treated with confidence. Verified is equivalent to attestation level A.
Not Verified means that, for this call, either the caller is not Verified, or it’s uncertain whether they have access to the caller ID used, or both. Not Verified means the call received attestation level B or C.
Not Applicable means STIR/SHAKEN doesn’t apply to this call, as would be the case if a call is not addressed to a US number or if it’s a cloud call (WebRTC or SIP).