COMPUTER FUNDAMENTALS

Detailed explanation-1: -A monoalphabetic cipher uses fixed substitution over the entire message, whereas a polyalphabetic cipher uses a number of substitutions at different positions in the message, where a unit from the plaintext is mapped to one of several possibilities in the ciphertext and vice versa.

Detailed explanation-2: -Traditionally, ciphers used these two main types of transformation: Transposition ciphers keep all the original bits of data in a byte but mix their order. Substitution ciphers replace specific data sequences with other data sequences.

Detailed explanation-3: -The simple substitution cipher The basic idea of a substitution cipher is a simple one: take one letter in your message, let’s say ‘A’, and replace it with a different letter, such as ‘E’. Sounds familiar? Both the Atbash and Caesar ciphers used this basic principle, however they both have one weakness: predictability.

Detailed explanation-4: -There are two basic methods of encryption: symmetric and asymmetric. Symmetric encryption uses the same key for encryption and decryption. Asymmetric uses a different key for encryption and decryption. A key is an external piece of information, like a password, used to cipher or decipher the code.

Detailed explanation-5: -Some algorithms that use the substitution technique are monoalphabetic substitution cipher, Playfair cipher, and polyalphabetic substitution cipher. The substitution cipher approach allows for the detection of plain text by low-frequency letters. Caesar Cipher is an example of the substitution cipher technique.