Authentication Security of Combinatorial Watermarking for GNSS Signal Authentication

Watermarking Signal Authentication is a technique where a GNSS provider cryptographically perturbs the spreading code to allow for limited cryptographic authentication of the signal. Several proposals and future studies exist or are underway to augment GNSS signals with this capability. This work reintroduces a generalized combinatorial watermarking function that affords a flexible pathway to cryptographically prove the authentication security of the signal with receiver observables. The security levels can be on-par with standard cryptographic security (e.g., 128-bit security) and require little or no additional use of the navigation data bandwidth. We show how our methods apply to signals of different designs and signal-to-noise ratios. From this work, one can design a Watermarking Signal Authentication scheme and the accompanying receiver to have high confidence in a signal’s authenticity.