Glossary
STIR/SHAKEN
A caller-ID authentication framework that lets carriers cryptographically sign and verify caller-ID information to reduce spoofed and spam calls.
also known as: Caller ID authentication, STIR, SHAKEN
STIR/SHAKEN is a pair of standards that lets phone carriers cryptographically sign caller-ID information when calls originate, and verify those signatures when calls terminate. The result: it’s much harder for spammers to spoof legitimate caller IDs.
The two parts
STIR (Secure Telephone Identity Revisited) - the cryptographic mechanism. When a call originates, the originating carrier signs the caller-ID with a digital signature tied to the carrier’s identity. When the call arrives at the destination, the terminating carrier checks the signature.
SHAKEN (Signature-based Handling of Asserted information using toKENs) - the deployment framework. SHAKEN defines how STIR is implemented across the carrier network, including the certificate authorities and attestation levels.
Attestation levels
- Full Attestation (A) - carrier verifies the caller is authorised to use the number.
- Partial Attestation (B) - carrier knows the customer but doesn’t verify the number ownership.
- Gateway Attestation (C) - carrier received the call but knows little about the source.
Terminating carriers can decide what to do with each level - block, label as “Suspicious”, or pass through unmarked.
Why it matters for Australian businesses
Inbound. Spam-call volume drops over time as STIR/SHAKEN deploys. Robocalls become harder. Genuine business calls get through more reliably.
Outbound. Legitimate outbound calls need proper attestation to avoid being labelled “Suspicious” or “Scam Likely” by the receiver’s carrier or phone. If your SIP trunk provider doesn’t support STIR/SHAKEN, your outbound calls may increasingly show as suspicious.
Number portability. Ported numbers still authenticate correctly if all carriers in the path support STIR/SHAKEN.
Status in Australia
The US mandated STIR/SHAKEN for major carriers in 2021. Australian rollout is progressive - major Australian carriers (Telstra, Optus, TPG) are at various stages of deployment. Smaller Australian SIP providers are catching up.
For CPS customers, our SIP infrastructure supports STIR/SHAKEN attestation for outbound calls so your numbers don’t get flagged as you scale outbound campaigns.
See also
- [[sip]] - protocol that carries the signed caller ID
- [[did-number]] - DID numbers benefit from STIR/SHAKEN authentication
- Spam reduction strategies for Australian business phone systems
