Secure communication requires encryption methods that strike a balance between efficiency and key protection. This study proposes a hybrid cryptosystem integrating the Hill Cipher and the RSA Cipher. The Hill Cipher, based on modular matrix multiplication, achieves fast encryption but lacks secure key distribution, whereas RSA provides robust asymmetric key management at a higher computational cost. By encrypting the Hill Cipher key with RSA, the proposed method strengthens resistance to brute-force and key compromise attacks. A Python-based implementation was developed and tested on messages of varying lengths. Experimental results show that the hybrid system maintains the efficiency of the Hill Cipher while significantly improving key security, with time complexity increasing modestly due to RSA key operations. Two scenarios were analyzed depending on whether the message length is divisible by the key matrix size, confirming the scheme’s flexibility. This approach demonstrates a practical and secure solution for protecting digital communication against cryptanalysis.
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