A phone call may connect in seconds, but how can the person receiving it know that the caller ID is genuine? With caller ID spoofing and fraudulent robocalls undermining confidence in voice communications, telecom providers need a reliable way to verify caller identity.
STIR/SHAKEN addresses this challenge through cryptographic caller authentication. It helps service providers verify the identity information associated with calls and strengthens the trust infrastructure behind modern voice networks. For telecom carriers, VoIP providers and enterprise communication platforms, understanding how STIR/SHAKEN works is an important step toward more secure and reliable voice communications.
1. What Is STIR/SHAKEN and Why Does It Matter?
Understanding the technology behind caller authentication
STIR/SHAKEN is a framework designed to combat caller ID spoofing by introducing cryptographic authentication into telephone networks.
The name combines two technical standards:
STIR (Secure Telephone Identity Revisited): A set of protocols developed by the Internet Engineering Task Force (IETF) that enables cryptographic verification of telephone identity information.
SHAKEN (Signature-based Handling of Asserted Information using toKENs): An implementation framework developed by the telecommunications industry to support consistent deployment of STIR across service provider networks.
Together, they allow originating providers to digitally sign call identity information and terminating providers to verify that information.
Traditional caller ID displays the number associated with a call but does not independently prove that the caller is authorized to use it. STIR/SHAKEN adds a verification mechanism that helps distinguish authenticated caller identity from potentially falsified information.
Why caller authentication is important
Consider a fraudster impersonating a bank by displaying its official customer-service number. A customer seeing that number may assume the call is legitimate.
STIR/SHAKEN helps providers authenticate caller identity information and gives downstream networks a way to verify the signature. It does not independently establish that the caller's intentions are legitimate, but it makes certain forms of caller ID manipulation more difficult.
For businesses that depend on telephone communication, this distinction is significant. Authentication strengthens the technical foundation of trust without replacing fraud detection, customer verification or other security measures.
2. How Does STIR/SHAKEN Work?
From call origination to identity verification
STIR/SHAKEN operates through a sequence of authentication and verification steps involving service providers and digital certificates.
Call origination: A customer places a call through an originating service provider. The provider evaluates the caller's identity and its relationship with the calling number.
Call authentication and signing: The originating provider creates a PASSporT token containing identity information and an attestation level. It uses a private key associated with its STIR/SHAKEN certificate to digitally sign the token.
Identity information travels with the call: The signed information is carried in a SIP Identity header so that downstream providers can access the authentication data.
Certificate retrieval and verification: The terminating provider retrieves the relevant public certificate and verifies the signature and associated identity information.
Call handling: The terminating provider can use the verification result to inform call handling or trust indicators, depending on its network capabilities and policies.
This process resembles a digitally signed document. The signature helps a recipient verify that the document was signed using the corresponding private key and that its signed content has not been altered.
The role of PASSporT and digital certificates
PASSporT is the signed token format used to convey telephone identity information. Digital certificates connect the signing key to an authorized service provider identity.
Both components are essential. A signature without a trusted certificate is difficult to validate against an established trust framework. Similarly, a valid certificate alone does not prove that a particular call was correctly authenticated.
This is why certificate issuance, secure key management and certificate availability are important parts of STIR/SHAKEN operations.
3. What Are the Three STIR/SHAKEN Attestation Levels?
Understanding A, B and C attestation
STIR/SHAKEN uses three attestation levels to communicate how much the originating provider can assert about a caller and the calling number.
| Attestation | Meaning | Example |
|---|---|---|
| A — Full attestation | The provider knows the customer and confirms the customer has the right to use the calling number. | A business places a call using a number assigned to its verified account. |
| B — Partial attestation | The provider knows the customer but cannot confirm the customer's right to use the calling number. | A known business uses a number whose authorization the provider cannot fully establish. |
| C — Gateway attestation | The provider can identify the point where the call entered its network but cannot establish the caller's identity and number authorization to the same degree. | A provider receives a call through an external gateway. |
These levels describe the originating provider's assertions. They are not universal fraud scores or guarantees that a call is safe. A-level attestation represents stronger identity and number authorization information, but even an authenticated call can be unwanted or fraudulent.
Why attestation matters to providers
Attestation helps downstream providers understand the authentication context of an incoming call.
For example, a contact center using several outbound numbers needs to ensure that its service provider has the necessary customer and number authorization information to sign calls appropriately.
This makes accurate number management and customer onboarding important parts of an effective authentication strategy.
4. How Does STIR/SHAKEN Protect Modern Voice Communications?
Reducing opportunities for caller ID spoofing
Caller ID spoofing is commonly used in impersonation scams. Fraudsters may display a number associated with a trusted organization to increase the likelihood that a recipient answers.
STIR/SHAKEN makes it possible for participating providers to verify signed caller identity information rather than relying only on the displayed number.
For example, when a bank's legitimate outbound call is authenticated, the receiving network can verify the signature and examine the attestation information. A spoofed call that lacks valid authentication may be treated differently under the receiving provider's policies.
This strengthens the network's ability to distinguish authenticated calls from calls with unverifiable identity information.
Supporting better decisions across the call path
Authentication results can help terminating providers inform call handling, display trust indicators or apply additional verification procedures.
However, STIR/SHAKEN has technical boundaries. Its effectiveness depends on participating networks, supported call paths and the preservation of authentication information. It does not encrypt the voice conversation or guarantee that a call will avoid spam labeling.
In practice, it works best as one component of a broader voice security strategy that may also include fraud analytics, number reputation systems and customer identity controls.
5. Why Certificate Management Is Essential for STIR/SHAKEN
Certificates keep the authentication process verifiable
Every signed call depends on a signing key and the certificate infrastructure that allows other providers to verify it.
A service provider must obtain authorization within the STIR/SHAKEN ecosystem before requesting certificates from an approved certificate authority. The process involves the STI Policy Administrator, provider identification and certificate issuance through an authorized CA.
Poor certificate management can introduce avoidable problems such as expired credentials, inaccessible certificates or incorrect configurations.
These issues can interfere with verification even when the call-signing system itself is operating correctly.
Automating certificate operations
As call volumes and network complexity increase, manual certificate handling can become difficult to maintain. Providers need processes for certificate issuance, renewal, revocation, secure key handling and certificate publication.
This is where specialized certificate authority services can help.
Peeringhub provides a STIR/SHAKEN certificate authority service with an ACME-based issuance workflow. Its platform also offers certificate repository hosting, an Identity Header Parser, a Certificate Inspector, OCN lookup, APIs and Python tooling.
For example, a VoIP provider can use certificate automation to simplify recurring certificate operations while using inspection tools to investigate authentication problems.
Automation can reduce repetitive administrative work, but providers must still maintain appropriate access controls and monitor the health of their signing and verification infrastructure.
6. How Do STIR/SHAKEN Providers Compare?
Different platforms serve different operational needs
Telecom providers can choose from solutions that focus on certificate issuance, complete authentication systems or broader communications platforms.
Peeringhub: Focuses on STIR/SHAKEN certificate authority services and certificate operations. Its capabilities include ACME automation, certificate hosting, certificate inspection, Identity Header analysis and developer tooling.
TransNexus: Offers a broader STIR/SHAKEN solution that includes authentication and verification services, secure key management, certificates and certificate repository hosting. Its platform is designed to integrate with existing network environments.
Twilio: Integrates SHAKEN/STIR into its communications platform. Its Trust Hub supports customer profile vetting, phone-number association and API-based onboarding for businesses using its voice services.
These offerings address overlapping but distinct needs. A provider looking primarily for certificate issuance and lifecycle automation may evaluate different capabilities from an enterprise seeking a complete programmable voice platform.
Choosing the right solution
Before selecting a platform, telecom operators should consider their existing network architecture, certificate requirements, automation needs and technical resources.
Key evaluation points include:
Certificate issuance and renewal workflows
API availability and integration options
Certificate repository support
Private-key management and security controls
Identity inspection and troubleshooting tools
Provider authorization requirements
Operational support and total cost
The right solution should fit the provider's existing infrastructure and the specific responsibilities it needs to manage.
Conclusion: Building More Trusted Voice Communications
STIR/SHAKEN introduces an important layer of security into modern voice communications by allowing providers to digitally authenticate caller identity information and enabling downstream networks to verify it.
Its effectiveness depends on more than signing calls. Reliable certificates, secure key management, accurate attestation and consistent handling of identity information all contribute to the authentication process.
For telecom carriers and VoIP providers, understanding these components is essential to building dependable voice infrastructure. As authentication becomes more integrated into network operations, certificate automation and verification tools can help simplify the work behind trusted communications.
Peeringhub helps providers manage the certificate infrastructure behind STIR/SHAKEN with automated issuance, certificate hosting, identity inspection and developer-friendly tools.
Visit www.peeringhub.io to explore its STIR/SHAKEN CA services and strengthen the foundation of your voice authentication infrastructure.
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