Data Encryption Standard (DES) for GTU INS Unit 2A

Download 1M+ code from https://codegive.com/c2974b2 okay, let's dive deep into the data encryption standard (des) for gtu's ins unit 2a. i'll provide a comprehensive explanation, covering the algorithm's steps, the key concepts, its strengths and weaknesses, and how it's implemented. i'll also include a basic python code example for demonstration, but keep in mind that a robust, production-ready des implementation is quite complex. **data encryption standard (des)** des is a symmetric-key block cipher algorithm. it's a *symmetric-key* algorithm because the same key is used for both encryption and decryption. it's a *block cipher* because it operates on fixed-size blocks of data at a time. specifically, des operates on 64-bit blocks of plaintext using a 56-bit key (actually, a 64-bit key with 8 bits used for parity checking). **overall architecture** the des algorithm can be summarized as follows: 1. **initial permutation (ip):** the 64-bit plaintext block is subjected to an initial permutation. this rearranges the bits of the plaintext according to a predefined table. this step doesn't provide any cryptographic strength; it's mostly historical. 2. **16 rounds of feistel network:** the permuted block is then processed through 16 rounds of a feistel network. each round involves: * dividing the 64-bit block into two 32-bit halves (l and r). * applying a round function *f* to the right half (r) and a round key *ksubi/sub*. * xoring the result of *f* with the left half (l). * swapping the left and right halves for the next round (except for the last round). 3. **final permutation (ipsup-1/sup):** after the 16 rounds, the left and right halves are concatenated, and a final permutation (the inverse of the initial permutation) is applied to produce the 64-bit ciphertext. **detailed breakdown of des steps** 1. **initial permutation (ip)** * the ip rearranges the bits of the 64-bit input block according to a predefined permutation table. * the purpose of ip is pri ... #GtuInsUnit2A #DataEncryptionStandard #python Gtu ins unit 2a data encryption standard DES cryptography symmetric key algorithm data security encryption techniques plaintext ciphertext key management block cipher cryptographic protocols information security digital privacy