This work describes the first proof-of-concept of mid-infrared (MIR) free-space cryptosystem, based on chaos synchronization between two distributed-feedback (DFB) quantum-cascade lasers (QCL), operating continuous wave at room temperature. Based on a superlattice heterostructure where the light emission is due to intersubband transitions, QCLs are now mature sources emitting in a wide range of wavelengths, from the MIR up to the long-wave infrared (LWIR, 2.6-20 μm) domains, extending also to the Terahertz region (60-150 μm). This feature, together with high output power and modulation bandwidth beyond tens of GHz, elects QCLs among the leading devices that find application in countless fields: countermeasure systems, high-resolution spectroscopy, and telecommunication.