<![CDATA[Rijndael is a symmetric-key block cipher cryptographic algorithm thatserves as the foundation for the Advanced Encryption Standard (AES),utilizing an identical secret key for both encryption and decryptionprocesses with selectable key lengths of 128, 192, or 256 bits. This studyaims to implement the Rijndael algorithm operating in Cipher BlockChaining (CBC) mode for securing various categories of digital files,encompassing documents (PDF), images (JPEG), and audio (MP3). Theresearch methodology follows an experimental and structured designcomprising literature study, system design, algorithm implementation,and empirical testing. Performance and security were evaluated throughfile capacity analysis, integrity preservation, quantitative metricsincluding Mean Square Error (MSE), Peak Signal-to-Noise Ratio(PSNR), and Avalanche Effect, alongside exhaustive/brute-force attacksimulations. The empirical results demonstrate that 256-bit Rijndaelsuccessfully encrypted and decrypted all tested digital files withoutaltering file sizes or compromising data integrity, exhibiting 0% file sizeoverhead. The generated ciphertexts were completely unidentifiablefrom the original plaintexts, while the decryption routine restored thedata to its original binary form with 100% fidelity. Quantitativeevaluations confirmed low distortion and high diffusion properties viathe Avalanche Effect, while brute-force simulations proved superiorcryptographic strength with increasing key length. This study concludesthat the Rijndael CBC algorithm provides an effective, storage-efficient,and robust security solution for digital file protection.]]>
