A post-quantum physical-layer encryption/decryption system based on chaotic Baseband Modulation Hopping (BMH). The baseband constellation, mapping, power level, and phase will vary symbol-by-symbol according to assigned random sequences. Pre-shared secret keys are used as the chaotic system parameters, initialization, and quantization parameters to generate the BMH codes. The BMH physical-layer encryption/decryption system can be combined with digital-domain based encryption algorithms such as AES, code-based post-quantum cryptography, and other physical-layer secure communication techniques such as Frequency Hopping (FH) and Direct Sequence Spread Spectrum (DSSS). It can also be combined with Quantum Key Distribution (QKD) to provide mutual authenticated key distribution. This invention can be applied to all kinds of communication systems including wireless (radio frequency, optical, quantum channel, sonar) and wire (optical fiber, power-line, telephone line, wire quantum channel, etc.), single carrier and multi-carrier, OFDM, MIMO channels.