STIR stands for Secure Telephone Identity Revisited — it is an IETF standard that defines how to digitally sign a call's originating identity using cryptographic certificates. SHAKEN stands for Signature-based Handling of Asserted information using toKENs — it is the implementation framework that governs how those signatures are applied by telephone service providers in practice. Together, STIR/SHAKEN creates a verifiable chain of trust from the originating carrier to the terminating network: when a signed call arrives, the receiving carrier can verify that the Caller ID was authenticated at source and has not been tampered with in transit.

Full Attestation (A) means the originating service provider has verified both the identity of the customer making the call and that the customer is authorised to use the presented phone number. Partial Attestation (B) means the provider has verified the call's origin but cannot confirm the customer is authorised to use that specific number — common for enterprise PBX or IP trunk scenarios. Gateway Attestation (C) is used when the call enters the signed network from an international gateway or an unauthenticated source, so only the entry point is verifiable. Receiving networks treat A-attested calls with the highest trust, B as intermediate, and C with increased scrutiny.

TRAI has been progressively developing its CLI authentication framework, and mandates for Caller ID authentication are being rolled out to licensed carriers. Enterprise organisations that originate high volumes of outbound calls are being asked to ensure their calls can receive appropriate attestation from their carrier. The regulatory landscape is still evolving — we flag the current TRAI compliance status of each listed provider and their commitment to updating their implementation as mandates develop. Organisations in BFSI, insurance and large-scale outbound operations should treat compliance as urgent rather than future-state planning.

STIR/SHAKEN operates at the SIP layer — the provider adds an Identity header to your outbound SIP INVITE containing the signed PASSporT token. For most deployments this is handled transparently by a signing service sitting between your Session Border Controller and the PSTN interconnect, so your SBC configuration requires minimal changes. The critical compatibility check is whether the signing service can integrate with your specific SBC vendor — Cisco Cube, Ribbon SBC, AudioCodes Mediant and Oracle ACME are all supported by listed providers. We confirm SBC compatibility during the matching process.

A-level attestation significantly reduces the likelihood of legitimate calls being mislabelled as spam by receiving carrier spam filters and apps like Truecaller, because it provides cryptographic proof that you are who your Caller ID claims to be. However, STIR/SHAKEN authentication does not override spam reputation scores built up by calling behaviour — high call volumes, low answer rates, or numbers that have been reported by recipients can still attract spam labels even on A-attested calls. Think of STIR/SHAKEN as a necessary foundation that removes the primary reason for mislabelling, not a guarantee against all filtering.

An STI-CA (Secure Telephone Identity Certificate Authority) is the body that issues the cryptographic certificates used to sign calls in a STIR/SHAKEN deployment. You do not need to operate your own STI-CA — your STIR/SHAKEN provider obtains certificates from a recognised authority and manages issuance, rotation and revocation on your behalf as part of the service. The key question when evaluating providers is whether their STI-CA relationship is with an authority that is recognised within the Indian SHAKEN ecosystem, as certificates from unrecognised CAs will not be validated by receiving networks. We confirm CA recognition status for every listed provider.