SpectraCert: A Hierarchical System for Dynamic Spectrum License Enforcement

While various spectrum sharing approaches aim to remedy the spectrum crunch and improve spectral utilization, they typically support only radios that are certified for and physically locked down to a single frequency band and power configuration. This limits their utility and re-usability as they do not support flexible license changes post-production, but there is generally no alternative dynamic technical license enforcement mechanism suitable for more flexible SDRs (Software-Defined Radios). This limits the utility of SDRs: SDR operators must use unlicensed bands, or obtain special permission from the FCC via a manual process. Further, they are subject to fines if they operate outside these bounds and/or interfere with other spectrum users. In response, we present SpectraCert--a dynamic, PKI-based (Public Key Infrastructure) system that enables safe, multi-faceted spectrum sharing while simultaneously enforcing license-holder rights directly within flexible transmitting radios. Entities receive specific frequency transmission rights from government authorities or other Spectrum-Authorized Entities (SAEs) through a spectracert : a certificate that specifies allowed frequencies and all required transmission conditions, such as allowed times, geographic areas, maximum transmit powers, expirations and more. Child spectracerts are derived from other spectracerts and have increasingly limited transmission rights, and trusted modules (TMs) within radios validate spectracert authenticity to ensure the rights defined by each parental spectracert are legal and not revoked. TMs only allow transmission according to validated spectracerts and control radio configurations. Spectracerts can also be used to verify SAE attestations of spectrum interference or occupancy reports. We implement a prototype of the SpectraCert system that automatically revokes or replaces spectracerts across SAE hierarchies when license updates occur, describe an integration with the OpenZMS spectrum management system, and evaluate how SpectraCert uniquely protects license rights while simultaneously allowing for more diverse, accessible spectrum sharing methods.