<![CDATA[This study presents a layered data-security design that combines Affine Cipher encryption with Pixel Value Differencing (PVD) image steganography. The first layer transforms plaintext into ciphertext using a monoalphabetic affine transformation, while the second layer conceals the ciphertext in neighboring image pixels according to local pixel differences. The method is reconstructed as a consistent Affine-PVD workflow and verified through deterministic worked examples rather than unsupported attack-success claims. Using the uppercase alphabet with keys a = 5 and b = 8, the plaintext “DATA” is transformed into “XIZI” and correctly recovered with the modular inverse. In the PVD verification, the pixel pair (100, 108) embeds the three-bit sequence 101 by changing the difference from 8 to 13, producing a valid modified pair (98, 111); extraction recovers the same bit sequence. These results confirm algorithmic reversibility of the two stages. The combined approach provides confidentiality and concealment as separate layers, but Affine Cipher remains a classical cipher and PVD is susceptible to steganalysis. Therefore, the design is appropriate as a prototype or instructional security model rather than a substitute for modern cryptographic protection.]]>
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