Somos Inc. Somos Inc. This document specifies a non-critical X.509 v3 certificate extension that conveys a set of self-asserted attributes describing the telephone numbers identified in the certificate's TNAuthList. The attributes are declared by the holder of the certificate about its own telephone numbers and require no separate authority token, because they describe or constrain only those numbers and grant no authority to any other party. The extension defines an extensible framework with an IANA registry of attribute types and seeds that registry with four types: a PASSporT Placement Service (PPS) URI, a do-not-originate indication, a do-not-originate-messaging indication, and a set of authorized originating providers. Relying parties use these self-declarations as policy signals, treating communications that do not conform to them as candidates for blocking. The mechanism is backward compatible with existing STIR certificates.