Hill Cipher Encrypt and Decrypt Messages Easily | Concept, Examples, and Applications of Hill Cipher

Algorithm for Hill Cipher 1. Key Preparation: - Choose a square key matrix (n × n) with non-zero determinant and ensure it's invertible mod 26. 2. Plaintext Processing: - Convert plaintext into numerical equivalents (A=0, B=1, ..., Z=25). - Divide plaintext into blocks of size n (matching the matrix size). 3. Encryption: - Multiply each plaintext block vector with the key matrix. - Apply modulo 26 to the result to get the ciphertext. 4. Decryption: - Compute the inverse of the key matrix modulo 26. - Multiply ciphertext blocks with the inverse key matrix and apply modulo 26. Advantages of Hill Cipher 1. Security via Mathematics: Uses matrix multiplication and modular arithmetic, making it mathematically robust. 2. Resistance to Frequency Analysis: Unlike substitution ciphers, Hill Cipher encrypts blocks of text, not individual letters, reducing susceptibility to letter frequency analysis. 3. Efficiency: Fast encryption and decryption due to the use of simple mathematical operations. 4. Flexible Block Size: Can work with block sizes greater than two, providing better security for longer plaintexts. Disadvantages of Hill Cipher 1. Key Sensitivity: Requires an invertible matrix as the key. If the determinant is 0 or not coprime with the modulus, decryption is impossible. 2. Vulnerability to Known-Plaintext Attacks: If enough plaintext-ciphertext pairs are known, the key can be deduced. 3. Computational Complexity: Decryption involves matrix inversion, which can be complex without computational tools. 4. Not Suitable for Modern Applications:Lacks robustness against advanced cryptanalytic methods and large-scale computation.