Securing Healthcare Data by Combining Cryptography and Steganography to Enhance Confidentiality

Background: Protecting Electronic Medical Records (EMRs) demands practical, low-overhead solutions. Methods: We propose a hybrid pipeline that encrypts patient medical records (PMRs) using an RNG-seeded substitution–transposition stage and hides the ciphertext via LSB steganography in radiological covers. The PRNG seed is derived from the user password as SHA-512(password) XOR-folded to an L-byte seed (L = 16 in experiments) and used to initialize a PRNG. Results: Evaluation on 60 PMR samples embedded in clinical covers (MRI/X-ray) shows high imperceptibility (average PSNR ≈ 65.6 dB, NMAE ≈ 0.0177) and strong cryptographic diffusion (aggregate NPCR ≈ 99.71%, UACI ≈ 33.27%). A key-sensitivity test (password vs password+"1") yielded NPCR ≈ 99.58% and UACI ≈ 33.30%, confirming keystream independence. Robustness tests (JPEG Q=90/70, Gaussian noise, median filtering, 10% cropping) demonstrate graceful degradation. Conclusion: We recommend operating at or below 0.005 bpp for reliable extraction or employing error correction and fragmentation for higher capacity. Performance profiling on commodity hardware (Intel i7-1165G7, 16 GB, .NET 4.6.2) shows per-operation times in the low hundreds of milliseconds.