A Dynamic Hybrid Cryptosystem Using Chaos and Diffie–Hellman Protocol: An Image Encryption Application

Images with sensitive content require encryption for storage and transmission. Symmetric schemes can cipher them, while an asymmetric cryptosystem distribute the secret key safely. For this reason, we propose a dynamic hybrid cryptosystem, which ciphers images transfers its private keys. It has symmetric algorithm that applies Lorenz equations generating different boxes permutations in every process round. Since concatenates two numbers, is included distribution. The proposal uses Diffie–Hellman protocol ElGamal obtaining seed building 128 strings. Then, SHA-512 applied each of them number times associated value blockchain representation. resultant strings are concatenated to conform public key. Finally, tests indicate resists differential, linear, algebraic, brute-force attacks. Its quality high according entropy, correlation, DFT, NPCR, UACI, AC, texture analysis, goodness fit test. Additionally, occlusion, additive, multiplicative, proposed χ2 noise attacks simulated on encrypted images. sharpness loss measured Similarity Parameter improved filter 5 × 5.