Optimizing Turbo Codes for Secret Key Generation in Vehicular Ad Hoc Networks

We present an algorithm that allows two users to establish a symmetric cryptographic key by incorporating the most important features of the wireless channel in vehicle-to-vehicle (V2V) communication. Non-reciprocity compensation is combined with turbo codes (TCs) for error reconciliation purposes. For fair comparisons, the indexing technique is applied in conjunction with the non-reciprocity compensation technique. A series of simulations are run to calculate key performance indicators (KPIs). High entropy values are obtained throughout all rounds of simulation during the key extraction process. Furthermore, simulation results indicate a significant improvement in bit mismatch rate (BMR) and key generation rate (KGR) when TCs are used. Increasing the number of iterations in the TC can significantly improve the Bit Error Rate (BER), thus generating more symmetric keys. The key generation rate was reported high ranging from 17 to 19 for the 256-bit symmetric keys per minute with TCs, while it is ranging from 2 to 5 when compared with a sample indexing technique published in the public domain. Finally, simulations proved also improvements for different key lengths as part of the error reconciliation process when TCs are used with an almost regular permutation (ARP) instead of a random permutation.