Exhaustive attack analysis of BBC with glowworm for unkeyed jam resistance

An important problem is to provide jam resistance for wireless networks. This is more difficult in cases such as GPS, where the sender and receiver do not have a shared secret that is unknown to the jammer. Currently, the only known system for such jam resistance without shared secrets is the BBC algorithm, which is fastest when it uses the Glowworm hash. We present a new type of analysis of Glowworm, using exhaustive search to find the absolutely best possible attack for reduced forms of Glowworm, as well as for the full Glowworm applied to shorter packets. Because we are defending against a stronger threat model (an adversary with infinite computational power), the analysis is actually easier than for a traditional threat model, and we derive much stronger results than would be possible for cryptographic hashes that are designed for a more traditional use. In addition, surprising results were found for its behavior near the boundary conditions. The result is that BBC with Glowworm can be used with great confidence, and it is now clear how to choose the best combination of parameters for practical use. 1