Computer Security: Data Encryption Standard (DES)
DES is a symmetric-key block cipher that follows the Fiestal Cipher structure. The steps involved in encryption are: Apply an initial permutation to the 64-bit input block using a permutation matrix Similar to the Fiestal Cipher structure, split the 64 bit output after permutation into 2 halves \(L_0\) (32 bits) and \(R_0\) (32 bits) Compute F(\(R_0\), \(k_0\)) using expansion, XOR, S-boxes, and permutation Set \(L_1\) = \(R_0\) and \(R_1\) = \(L_0\) XOR F(\(R_0\), \(k_0\)) Now, this concludes the first round. Now, do steps 3-4 15 more times After round 16, perform a 32-bit swap like in Fiestal Cipher structure Undo the initial permutation to get the cipher text ...