STIR/SHAKEN and Caller ID Authentication: What It Means for Your Outbound Campaigns

STIR/SHAKEN (Secure Telephone Identity Revisited / Signature-based Handling of Asserted information using toKENs) is the cryptographic call authentication framework mandated by the FCC for US voice carriers since 2021. It works by digitally signing the caller ID information at the originating carrier using a certificate, which downstream carriers verify. The verification result is an attestation level—A, B, or C—that indicates how confident the originating carrier is in the caller ID's authenticity.

Attestation Levels Explained

• Full Attestation (A): The originating carrier has verified that the calling party is authorized to use the number being presented as caller ID. This is the strongest signal and results in the best display treatment at the terminating carrier. Achieving A attestation requires that your VoIP provider has verified your ownership or authorization to use the specific DID you are calling from.
• Partial Attestation (B): The originating carrier has verified the customer's identity but cannot confirm they are authorized to use the specific number. Common when a call center uses numbers not registered with the originating carrier or uses a different CID than their assigned DID pool.
• Gateway Attestation (C): The call entered the IP network from an unknown source—typically from a TDM gateway or an overseas call center. C-attested calls receive the worst treatment from terminating carriers and are most likely to be labeled spam.

How to Achieve and Maintain A Attestation

• Register your DIDs with your originating VoIP provider and ensure your campaign caller IDs match your registered DID pool. Do not present a caller ID from a number block you do not control.
• Avoid spoofing caller IDs to display local area codes you are not assigned. Local presence dialing that uses numbers outside your registered DID pool will receive B attestation at best and is a common cause of spam labeling.
• Work with a carrier that participates in the FCC's Robocall Mitigation Database and maintains active STIR/SHAKEN certificates. Not all VoIP providers sign calls—some pass calls unsigned, resulting in C attestation at the terminating end.