TL;DR
Quick Answer
TL;DR
Key Facts
- Originating service providers: The provider that originates and signs a call is responsible for applying STIR/SHAKEN authentication and assigning attestation levels.
- Attestation decisions: The signing provider determines the appropriate attestation level based on its knowledge of the caller and the caller's authorization to use the number.
- Direct carrier relationships: When an enterprise connects directly to a carrier, that carrier typically signs the calls.
- Indirect provider relationships: When calls originate through a Communications Platform as a Service (CPaaS), Unified Communications as a Service (UCaaS), wholesale provider, reseller, or other intermediary, that provider may be responsible for signing the call.
- STIR/SHAKEN certificates: Certificates are issued to eligible voice service providers participating in the STIR/SHAKEN ecosystem, not directly to most enterprises.
- Regulatory obligations: Voice service providers implementing STIR/SHAKEN must meet Federal Communications Commission (FCC) requirements and participate in the Secure Telephone Identity (STI) governance framework.
- Enterprise visibility: Organizations should understand which provider is signing their calls because attestation outcomes, authentication issues, and remediation often depend on that provider relationship.
Who Signs My Calls With STIR/SHAKEN?
STIR/SHAKEN call signing occurs at the provider level, not the enterprise level.
The voice service provider that originates the call into the Session Initiation Protocol (SIP) network is generally responsible for digitally signing the call and assigning an attestation level. That provider uses its STIR/SHAKEN certificate to authenticate caller ID information and indicate its level of confidence that the caller is authorized to use the telephone number being displayed.
In practical terms, enterprises do not typically sign their own calls or obtain STIR/SHAKEN certificates directly. Instead, they rely on authorized voice service providers to perform authentication on their behalf.
Who signs your calls depends largely on how your organization connects to the voice ecosystem. A carrier may sign the call, or an upstream provider such as a CPaaS, UCaaS, wholesale provider, or other telecommunications partner may perform that function.
How It Works
How Does Call Signing Work?
When a call is placed, the originating provider evaluates its relationship with the caller and the telephone number being used.
The provider then:
- Authenticates the caller information.
- Determines the appropriate attestation level.
- Digitally signs the call using its STIR/SHAKEN certificate.
- Transmits the signed call into the voice network.
Downstream providers can then validate the signature and authentication information as the call moves through the network.
Who Can Obtain a STIR/SHAKEN Certificate?
STIR/SHAKEN certificates are generally obtained by authorized voice service providers that participate in the Secure Telephone Identity ecosystem.
To participate, providers typically must:
- Meet eligibility requirements established by the Secure Telephone Identity Governance Authority (STI-GA) and Policy Administrator framework.
- Obtain a Service Provider Code (SPC) token.
- Obtain a Secure Telephone Identity certificate.
- Comply with applicable FCC caller authentication requirements.
Because the framework is designed around provider-level authentication, most enterprises do not directly obtain certificates or sign calls themselves. Instead, they work through providers that perform these functions.
How Do Provider Relationships Affect Attestation?
The entity signing your calls is not always the company with which you have a direct commercial relationship.
For example:
- If you purchase voice services directly from a carrier, that carrier will often sign your calls.
- If you use a CPaaS platform, cloud contact center, business process outsourcer, or reseller, another upstream provider may perform the signing function.
- In complex provider chains, multiple service providers may be involved before a call reaches its destination.
As a result, enterprises are sometimes unaware of which provider is making attestation decisions or how those decisions are determined.
Why This Matters
Why Should Enterprises Know Who Is Signing Their Calls?
Organizations often focus on attestation outcomes without understanding which provider is actually responsible for generating them.
When authentication issues arise, understanding who signed the call is important because that provider generally controls:
- Attestation assignment
- Caller ID authentication policies
- Number authorization validation
- Authentication troubleshooting
- Remediation of signing-related issues
Without visibility into the signing provider, enterprises may have difficulty identifying where authentication issues originate or who can resolve them.
How Does This Affect Call Performance?
Authentication outcomes can influence how calls are processed within the voice ecosystem.
If attestation levels are unexpectedly low or authentication information is missing, enterprises may need to work with the signing provider to understand:
- Whether telephone number authorization has been verified
- Whether caller identity records are accurate
- Whether provider onboarding requirements have been satisfied
- Whether technical or routing issues are affecting authentication
Understanding who signs calls can help reduce delays when investigating call-delivery challenges.
Why Is Transparency Important?
Modern call paths can involve multiple carriers, platforms, and service providers. The more complex the provider chain becomes, the more important transparency becomes.
Organizations benefit when they can clearly answer:
- Who authorizes our telephone numbers?
- Who signs our calls?
- Who assigns attestation levels?
- Who manages authentication issues?
- Who is responsible for remediation when problems occur?
This visibility can improve accountability, support troubleshooting efforts, and help ensure caller identity information is consistently authenticated throughout the call lifecycle.
Common Questions
Can an enterprise obtain its own STIR/SHAKEN certificate?
Generally, no. STIR/SHAKEN certificates are typically issued to eligible voice service providers that participate in the Secure Telephone Identity (STI) ecosystem, not directly to most enterprises. Because call authentication occurs at the provider level, organizations usually rely on their carrier, Communications Platform as a Service (CPaaS) provider, or other voice service provider to sign and authenticate calls on their behalf.
Who decides whether a call receives A-Level, B-Level, or C-Level Attestation?
The originating service provider signing the call determines the attestation level. That decision is based on the provider's knowledge of the caller and its confidence that the caller is authorized to use the telephone number being displayed. Higher attestation reflects greater confidence in the caller's identity and number authorization, but it does not indicate whether the call is wanted or trustworthy.
Can my carrier and my CPaaS provider both sign my calls?
Typically, only one provider applies the STIR/SHAKEN signature associated with the call origination event. However, in multi-provider environments, it is not always obvious which provider is ultimately responsible for authentication and attestation decisions. If you are unsure, ask your provider which entity is originating and signing calls on your behalf.
How can I find out who is signing my calls?
The best way is to ask your voice service provider directly. Depending on your communications architecture, the company that bills you may not be the same company that signs your calls. Understanding who performs STIR/SHAKEN authentication can help you troubleshoot attestation issues, caller ID authentication failures, and questions about number authorization.
Does signing a call guarantee it will not be labeled as spam?
No. STIR/SHAKEN signing and attestation authenticate caller ID information and help establish that a caller is authorized to use a number. Spam labeling is typically determined through separate reputation and analytics systems that evaluate calling behavior, complaints, and other risk signals. As a result, even fully authenticated calls can still receive Spam or Scam labels.
Our platform empowers organizations to manage branded calling, improve caller id reputation, and stay compliant with evolving regulatory and industry standards. FAQs and Glossary terms like this are designed to provide clear, actionable guidance backed by our expertise in verified identity, call labeling mitigation, and spam prevention.
To explore how Numeracle supports trusted and effective outbound communications, visit www.numeracle.com.
