STIR/SHAKEN Architecture: Mitigating Caller ID Spoofing and Carrier Blocking

Caller ID spoofing has systemically degraded trust in global telecommunications. In response, regulatory bodies mandated the implementation of the STIR/SHAKEN framework. STIR (Secure Telephone Identity Revisited) and SHAKEN (Signature-based Handling of Asserted Information Using toKENs) form a suite of protocols and procedures operating at the SIP (Session Initiation Protocol) layer to cryptographically validate caller identity.

Deploying outbound telecom infrastructure without native STIR/SHAKEN signing guarantees packet termination. Terminating carriers algorithmically drop or flag unsigned SIP INVITEs as "Scam Likely" or "Spam Risk," devastating connection rates.

The Cryptographic Handshake

STIR/SHAKEN operates on public key cryptography. When an outbound call is initiated, the originating service provider utilizes an encrypted digital certificate to generate a SIP Identity header. This header contains an encrypted token detailing the calling number, the called number, and the timestamp.

Digital certificates are authenticated against an authorized STI Certificate Authority (STI-CA).

Upon receiving the SIP INVITE, the terminating service provider intercepts the packet, queries a public certificate repository to decrypt the token, and validates the signature. If the cryptographic hash matches the packet data, the call is verified.

Attestation Levels Defined

Validation is not binary; it is tiered based on the originating provider's relationship with the caller.

• Full Attestation (A-Level): The provider authenticates the customer and verifies they possess authorization to utilize the specific caller ID. This is the only acceptable baseline for enterprise outbound traffic.
• Partial Attestation (B-Level): The provider authenticates the customer but cannot verify their authorization to use the specific caller ID (common in poorly configured PBX deployments).
• Gateway Attestation (C-Level): The provider can authenticate the point of entry into their network but has no verifiable relationship with the caller. Terminating networks routinely block C-Level traffic.

Native Compliance in Eleven Solutions

Implementing STIR/SHAKEN via third-party SBCs (Session Border Controllers) introduces unnecessary latency and points of failure in the SIP signaling path.

Eleven Solutions engineers STIR/SHAKEN compliance directly into the core switching logic. By enforcing strict KYC (Know Your Customer) verifications during onboarding and SIP trunk provisioning, Eleven Solutions guarantees A-Level Attestation for all authenticated outbound traffic. The infrastructure autonomously signs the SIP Identity header prior to network egress, ensuring downstream terminating carriers receive flawless cryptographic validation.

A-Level Attestation directly correlates to maximized Answer Seizure Ratios (ASR).

Relying on legacy carriers that fail to provide A-Level signing is a mathematical vulnerability in your sales or support pipeline. Configure your SIP trunks through validated providers to secure your outbound routing architecture.