What is STIR/SHAKEN?
STIR/SHAKEN is the United States caller-ID authentication framework. STIR is the cryptographic signing standard from the IETF. SHAKEN is the carrier-deployment profile. Together they let receiving carriers verify that a calling number was actually signed by the originating carrier rather than spoofed.
The three attestations
Originating carriers sign every call with one of three attestation levels. A (full) means the carrier verified both the caller and their right to use the number. B (partial) means the carrier knows the caller but cannot verify the number. C (gateway) means the carrier is just passing it on. A is the goal.
What you see
Calls with attestation A are less likely to be labeled "Spam Likely" on the recipient's screen. Calls with attestation C from unknown sources are more likely to be filtered. The labeling decision is made by the terminating carrier and downstream apps; STIR/SHAKEN provides the input signal.
message.com handling
All outbound calls from message.com DIDs are signed with attestation A by our upstream carrier. Inbound call events expose the verification result so you can spot spoofed callers. See the STIR/SHAKEN concept page for the full technical write-up.
See it working on message.com.
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