What is STIR/SHAKEN?
What is STIR/SHAKEN?
Section titled “What is STIR/SHAKEN?”STIR/SHAKEN is a mandatory call authentication framework deployed across North America to verify the identity of inbound calls and reduce illegal caller ID spoofing.
- STIR — Secure Telephony Identity Revisited: verifies call identity over VoIP networks
- SHAKEN — Signature-based Handling of Asserted information using toKENs: extends verification to traditional (non-VoIP) cellular and PSTN calls
Both are overseen by the CRTC (Canadian Radio-television and Telecommunications Commission) in Canada and the FCC (Federal Communications Commission) in the United States.
Why STIR/SHAKEN Exists
Section titled “Why STIR/SHAKEN Exists”When a spoofed call is placed, the fraudulent caller ID can display any number — impersonating banks, government agencies, or even the recipient’s own number. Opting for an unknown or private caller CNAM results in only about a 19% answer rate in the US, so scammers steal real numbers to increase pickup rates and fraud effectiveness.
STIR/SHAKEN creates a cryptographic “attestation” attached to calls that travels with the call through the network, allowing receiving carriers to verify whether the number is legitimate.
How It Works
Section titled “How It Works”STIR uses three attestation levels:
| Attestation | Meaning |
|---|---|
| A — Full Attestation | The originating carrier knows the customer and confirms they are authorized to use the number |
| B — Partial Attestation | The carrier knows the customer but cannot confirm the number is assigned to them |
| C — Gateway Attestation | The call entered the network from an unknown or unverified source |
When a call arrives at the receiving carrier, SHAKEN reads the attestation token and surfaces a tag to the recipient (such as “Verified” or “Spam Likely” depending on the level).
Does STIR/SHAKEN Block Spoofed Calls?
Section titled “Does STIR/SHAKEN Block Spoofed Calls?”No. STIR/SHAKEN verifies calls — it does not automatically block unverified ones. A call without attestation (C-level or missing token) may still be delivered; the carrier or recipient decides how to treat it.
This is an important distinction:
Implementation Status
Section titled “Implementation Status”STIR/SHAKEN has been mandated for major carriers in both the US and Canada. Smaller carriers (fewer than 100,000 subscribers in the US) received phased implementation timelines. Full implementation across all carriers is ongoing.
SIPSTACK implements STIR/SHAKEN attestation for all outbound calls originating through the platform.