Authenticated delivery of BB84-keyed messages through lossy image channels using hardware-derived keys

Abstract Pipelines that key image-based information hiding with quantum key distribution (QKD) assume the stego image arrives bit-exact, and keys from noisy quantum hardware are unusable without reconciliation. This work addresses both. BB84 runs on IBM’s ibm fez are reconciled with Cascade, confirmed by hashing and compressed by Toeplitz privacy amplification; at 4096 qubits every run yields 1,110–1,237 secure bits, identical for both parties, at a quantum bit error rate of at most 0.98%. The keys protect messages with authenticated encryption, Reed– Solomon coding and key-driven embedding in discrete cosine transform (DCT) or wavelet domains. A pre-registered evaluation on 300 images shows that a key-driven least-significant-bit reference scheme, representative of lossless-channel designs, recovers 0 messages after JPEG recompression, while coded DCT embedding delivers at least 99% of messages at every quality tested; restricted post hoc to images above 40 dB peak signal-to-noise ratio, it carries 0.218 bits per pixel at quality 95 and 0.005 at quality 50. A hardware-keyed message decrypts and verifies after JPEG quality 50. This robustness costs detectability: at the smallest payload tested, a simple learned detector separates the robust variants from covers with an area under the curve of at least 0.797, against 0.517 for the reference scheme. The keys characterize hardware noise rather than deployable secrecy, and the security estimate is asymptotic.