STIR/SHAKEN

STIR/SHAKEN (Secure Telephony Identity Revisited / Signature-based Handling of Asserted information using toKENs) is a framework of technical standards that cryptographically verifies the caller ID displayed on outbound calls. Mandated by the FCC for most carriers, STIR/SHAKEN assigns attestation levels (A, B, or C) to each call based on how confidently the originating carrier can verify the caller’s right to use the displayed number.

How It Works in VICIdial

STIR/SHAKEN is implemented at the carrier level, not within VICIdial itself. When VICIdial places an outbound call through a SIP trunk, the carrier examines the outbound CID and assigns an attestation level: A (Full — the carrier can verify the caller has the right to use the number), B (Partial — the carrier knows the customer but cannot verify the specific number), or C (Gateway — the call originated from a gateway with no verification).

The attestation level is embedded in a cryptographic SIP header (Identity header) that travels with the call. The terminating carrier reads this header and may use the attestation level to influence call treatment — A-level calls are typically delivered normally, while C-level calls may be flagged as “Spam Likely” or blocked entirely.

For VICIdial operations, achieving A-level attestation requires that the DIDs used as outbound CID are provisioned through the same carrier that signs the calls, and the carrier has verified your organization’s right to use those numbers.

Why It Matters

STIR/SHAKEN has dramatically changed outbound calling. Calls without attestation or with low attestation levels (B or C) see significantly lower answer rates because recipient carriers and phone apps flag or block them. Operations that previously rotated CIDs through numbers they did not own (a once-common practice) now face call blocking.

For VICIdial operators, STIR/SHAKEN compliance means working with carriers that provide A-level attestation, using only authorized DIDs as outbound CID, and maintaining proper number registration. See our STIR/SHAKEN VICIdial guide and the DID hygiene feature page for implementation strategies.