Study of Full Attestation Alternatives for Enterprises and Business Entities with Multi-Homing and Other Arrangements (ATIS-1000089.v002)

This Technical Report describes use cases where a Signature-based Handling of Asserted information using
toKENs (SHAKEN) Originating Service Provider (OSP) may not have complete locally available information to
establish a verified association between a calling telephone number (calling TN) and its direct Customer, as the
basis for assigning a “full attestation” value to particular calls. In addition, this report summarizes a few different
mechanisms: Delegated Certificates, Extended Validation (EV) Certificates with TN Letter of Authorization (TNLoA),
and Central TN Database, that have been proposed to provide the OSP with additional information regarding the
entity placing a call and the telephone numbers that entity has a valid association with in order to support the OSP
marking the call with the highest attestation level. All three approaches are considered viable; however, they do
present different tradeoffs in terms of complexity, cost to service providers and enterprises, and the assumptions
around the relationship between service providers, their customers, and other entities in the SHAKEN and voice
network ecosystems. It is difficult to predict how these tradeoffs will influence industry acceptance of one solution
over another, and it is likely that the “best” solution will vary based on the deployment use case. Published 2021-05-12.