STIR/SHAKEN
Short answer: STIR/SHAKEN is a caller ID authentication framework that lets phone carriers digitally sign and verify the calling number on IP calls, to combat spoofed robocalls. The FCC requires US voice providers to implement it, and it is also used in Canada.
STIR refers to the IETF standards for signing caller ID; SHAKEN is the industry framework that applies them across carrier networks.
How it works
The originating carrier adds a signed Identity header (a PASSporT token, RFC 8224 and RFC 8225) to the SIP call, with an attestation level: A (full, the carrier knows the customer and number), B (partial) or C (gateway). The terminating carrier verifies the signature with the signer's certificate and can use the result in call labeling or blocking.
STIR/SHAKEN attestation levels
| Level | Meaning |
|---|---|
| A (full) | The carrier knows the customer and the number |
| B (partial) | Partial attestation |
| C (gateway) | Gateway attestation |
How it applies to ZuteSIP
STIR/SHAKEN is not listed as a ZuteSIP feature, and ZuteSIP does not state attestation levels for calls. It is handled by carriers in the networks a call passes through.
Related terms
- Caller ID
- CNAM
- SIP
Frequently asked questions
What does attestation A mean?
The signing carrier verified the customer and their right to use the calling number.
Does STIR/SHAKEN block calls?
It verifies caller ID; carriers may use the result, among other signals, to label or block calls.
Does ZuteSIP provide STIR/SHAKEN attestation?
It is not a listed ZuteSIP feature.
Related pages
- caller ID
- CNAM
- SIP
- US phone number from abroad
- call centers use case
- acceptable use policy
- Softphone
- Toll-Free Number
Sources
- FCC: Combating Spoofed Robocalls with Caller ID Authentication (as of September 2026)
- IETF: RFC 8224, Authenticated Identity Management in SIP (as of September 2026)
- IETF: RFC 8588, PASSporT Extension for SHAKEN (as of September 2026)