Digital content distribution and proprietary 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. We present a location-dependent cryptosystem in which the decryption key is not transmitted as human- or machine-readable data, but implicitly encoded in precise time-of-flight differences of ultra-wideband (UWB) data transmission packets. The system leverages precise timing hardware and a custom TiCK (Timing-encoded Cryptographic Keying) protocol to map a SHA-256 hashed AES key onto scheduled transmission timestamps. Only receivers located within a predefined spatial region can observe the packet timings that align with the intended "time slot" pattern, enabling them to reconstruct the key and decrypt the secret. Receivers outside the authorized region observe incorrect keys. We implement a complete prototype that encrypts and transmits audio data using our cryptosystem, and only when the receiver is within the authorized data, they are able to decrypt the data. 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.

翻译：数字内容分发和专有研究驱动型行业持续面临知识产权盗窃和未经授权再分发的风险。传统的加密方案（如AES、TDES、ECC和ElGamal）虽能提供强大的密码学保证，但其本质上对解密发生的位置不敏感。实践中，这意味着一旦解密密钥泄露或被截获，任何攻击者都可在任意位置滥用该密钥解密受保护内容。本文提出一种位置依赖密码系统，其解密密钥并非以人类或机器可读的数据形式传输，而是隐式编码在超宽带（UWB）数据传输数据包的精确飞行时间差中。该系统利用精确定时硬件和自定义的TiCK（时序编码密码密钥）协议，将SHA-256哈希化的AES密钥映射到预定的传输时间戳上。只有位于预定义空间区域内的接收器才能观测到与预期"时隙"模式匹配的数据包时序，从而重建密钥并解密密文。区域外的接收器则获得错误密钥。我们实现了完整原型系统，使用该密码系统加密并传输音频数据，仅当接收器位于授权区域内时才能成功解密数据。评估结果表明，该系统（i）消除了以电子或物理方式共享解密密码的需求，（ii）确保窃听者无法恢复解密密钥，且（iii）为合法用户提供了显著的空间容错能力。