The best known multiple letter encryption cipher is the , which treats digrams in the plaintext as single units and translates these units into ciphertext digrams

Playfair Cipher.

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.

The best known multiple letter encryption cipher is the Playfair Cipher, which treats digrams in the plaintext as single units and translates these units 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.