How to repair the Hill cipher
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- Ismail, I.A., Amin, M. & Diab, H. J. Zhejiang Univ. - Sci. A (2006) 7: 2022. doi:10.1631/jzus.2006.A2022
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The Hill cipher algorithm is one of the symmetric key algorithms that have several advantages in data encryption. However, a main drawback of this algorithm is that it encrypts identical plaintext blocks to identical ciphertext blocks and cannot encrypt images that contain large areas of a single color. Thus, it does not hide all features of the image which reveals patterns in the plaintext. Moreover, it can be easily broken with a known plaintext attack revealing weak security. This paper presents a variant of the Hill cipher that overcomes these disadvantages. The proposed technique adjusts the encryption key to form a different key for each block encryption. Visually and computationally, experimental results demonstrate that the proposed variant yields higher security and significantly superior encryption quality compared to the original one.