Cryptography Assignment 2022

CRYPTOGRAPHY

PUBLIC KEY AND SECRET KEY CRYPTOGRAPHY
Two major ideas used for encryptions are cryptography of public key and secret key.
Data encrypted using public key can be decrypted only with private key and data
encrypted using private key can be decrypted only with public key.
In secret key system, one single key is used only for decryption and encryption.
Transmitters and receivers have same secret key.

SUBSTITUTION CIPHERS AND TRANSPOSITION CIPHERS
In encryption algorithm, two major techniques are used in implementation of secret key
cryptography: Transposition cipher and substitution cipher.
Characters or bits are rearranged in data by transposition ciphers.
Transposition technique can be achieved by applying permutation on letters of plaintext.
Characters, bits or characters block are replaced with substation by substitution ciphers.
Substitution ciphers use single mapping which means same plaintext would have similar
ciphertext. This problem can be solved by polyalphabetic cipher with the use of multiple
substitutions.