1. Explain DES with its structure. Also explain its function.
Ans.: Data Encryption Standard (DES) is a symmetric-key block cipher that was first published in 1977 by National Institute of Standards and Technology (NIST). It was originally proposed by IBM in 1973 in response to the request for proposals for a national symmetric-key cryptosystem. This encryption standard was adopted by the US government for non-classified information and by various industries for use in security products. DES is also known as the Data Encryption Algorithm (DEA) by ANSI and DEA-1 by ISO.
At the sender's end, DES divides the plaintext into 64-bit blocks and encrypts each block using a 56-bit cipher key to produce a 64-bit ciphertext ...