GeoGuard: UWB Timing-Encoded Key Reconstruction for Location-Dependent, Geographically Bounded Decryption

Digital content distribution and propitiatory research driven industries face persistent risks from intellectual property theft and unauthorized redistribution. Conventional encryption schemes such as AES, TDES, ECC, and ElGamal provide strong cryptographic guarantees, but they remain fundamentally agnostic to where decryption takes place. In practice, this means that once a decryption key is leaked or intercepted, any adversary can misuse the key to decrypt the protected content from any location. This paper presents, GeoGuard, a location-dependent cryptosystem in which the decryption key is not transmitted as data but is implicitly encoded in the precise time-of-flight differences of ultra-wideband (UWB) data transmission packets. The system leverages precise timing hardware and a custom Timing-encoded Cryptographic Keying (TiCK) protocol to map a 32-byte SHA-256 AES key onto scheduled transmission timestamps. Only user located within an approved spatial location can observe the correct packet timing that aligns with the intended packet-reception timing pattern, enabling them to reconstruct the key. Eavesdroppers outside the authorized region observe an incorrect timing pattern, which yields incorrect keys. GeoGuard is designed to encrypt and transmit data, but decryption is only possible when the user is within the authorized area. Our evaluation demonstrates that the system (i) removes the need to share decryption passwords electronically or physically, (ii) ensures the decryption key cannot be recovered by the eavesdropper, and (iii) provides a non-trivial spatial tolerance for legitimate users