Guaranteed Caller® (GC) ensures Caller ID attestation and verification through compliant implementation of mandatory STIR/SHAKEN protocols and procedures.

With Guaranteed Caller, Service Providers can acquire digital certificates from netnumber as an official Secure Telephone Identity Certification Authority (STI-CA) in the U.S. These certificates and appropriated trust levels are added to the Session Initiated Protocol header, effectively signing outbound calls. Inbound calls are evaluated by verifying their trust level and signature. Guaranteed Caller is a cloud service supporting protocol standards like SIP, ACME and ATIS-1000082.