Comparative Analysis of Hybrid Cryptosystems for Secure Image Encryption

Traditional encryption systems, such as DES and Triple DES, face challenges when applied to images due to their high redundancy and large size. To address these challenges, this paper explores secure image encryption by comparing two hybrid cryptosys-tems, AES-256-GCM-SHA384 and ChaCha20-Poly1305-SHA256. Implemented locally in Python, these systems use the Elliptic Curve Diffie-Hellman (ECDH) algorithm for key exchange and their respective algorithms for bulk encryption, similar to those used in TLS 1.3. This work evaluates the performance and security of these systems using metrics including Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), Structural Similar-ity Index (SSIM), entropy, total encryption/decryption process time, Number of Pixel Change Rate (NPCR), Unified Average Changing Intensity (UACI), correlation coefficients, and Bit Error Rate (BER). A dataset of 10 satellite images is used for testing. The results show that AES-based cryptosystems outperform ChaCha20-based systems in speed, and both exhibit robust security features. Visual analysis, histogram, and correlation plots further validate the strength of the encryption. The paper concludes with proposed future research directions, including analysis of various image types, integration of post-quantum cryptography, and exploration of lightweight cryptography for resource-constrained PKI environments.