It is well-known that monoalphabetic substitution cipher (also known as monoalphabetic cipher) is not secure, because it can be subjected to frequency analysis. a. True
b. False

a. True

Explanation:

Encryption is a form of cryptography and typically involves the process of converting or encoding informations in plaintext into a code, known as a ciphertext. Once, an information or data has been encrypted it can only be accessed and deciphered by an authorized user.

Some examples of encryption algorithms are 3DES, AES, RC4, RC5, and RSA.

It is well-known that monoalphabetic substitution cipher (also known as monoalphabetic cipher) is not secure, because it can be subjected to frequency analysis.

The Playfair Cipher is generally considered to be the best multiple letter encryption cipher because it processes digrams in the plaintext as singular units and translates them directly into ciphertext digrams.

In the Playfair Cipher, a 5 × 5 matrix comprising of letters is developed using a keyword and then, the matrix is used to encrypt the plaintext as a pair i.e two letters at a time rather than as a single text.