During sensitive military operations, such as air operations in theater, the broadcasting of ADS-B messages poses a serious security concern, but the small message payload of ADS-B transmissions renders encryption standards such as AES unsuitable. Format-preserving encryption (FPE), a technique already in use on small message sizes such as credit card numbers, provides a suitable implementation of strong symmetric key encryption for the military context. This research proposes and details a Secure ADS-B (SADS-B) system which utilizes a bump-in-the-wire approach for encryption and decryption of ADS-B messages using FPE, going on to then characterize the prototype\u27s performance using the following metrics: detection and error rates, operational latency, and utilization of resources on the underlying field programmable gate array (FPGA) hardware. Findings include sub-millisecond operational latency, full data rate throughput capability for ADS-B, and approximately 50% utilization of the available FPGA resources. Overall, findings suggest that a layered security system such as SADS-B is suitable for adding confidentiality to ADS-B
