Variable-length Hill Cipher with MDS Key Matrix
This work addresses security improvements for classical symmetric ciphers, but it is incremental as it builds on existing Hill Cipher modifications.
The paper tackled the vulnerability of the Hill Cipher to cryptanalysis by proposing a variable-length key matrix derived from an MDS master key matrix, resulting in strengthened security against known-plaintext attacks.
The Hill Cipher is a classical symmetric cipher which breaks plaintext into blocks of size m and then multiplies each block by an m by m key matrix to yield ciphertext. However, it is well known that the Hill cipher succumbs to cryptanalysis relatively easily. As a result, there have been efforts to strengthen the cipher through the use of various techniques e.g. permuting rows and columns of the key matrix to encrypt each plaintext vector with a new key matrix. In this paper, we strengthen the security of the Hill cipher against a known-plaintext attack by encrypting each plaintext matrix by a variable-length key matrix obtained from a Maximum Distance Separable (MDS) master key matrix.