# What is the rule of encryption in playfair cipher?

Table of Contents

- 1 What is the rule of encryption in playfair cipher?
- 2 What are the rules of pairing in case of Playfair?
- 3 What are the various rules to encrypt the plaintext by using Playfair?
- 4 What type of cipher is Playfair?
- 5 What will be the size of a key matrix if the plain text is secret?
- 6 Is Playfair cipher a block cipher?

## What is the rule of encryption in playfair cipher?

When the two letters are in different rows and columns, each is replaced by the letter that is in the same row but in the other column; i.e., to encrypt WE, W is replaced by U and E by G. When A and R are in the same row, A is encrypted as R and R (reading the row cyclically) as M.

## What are the rules of pairing in case of Playfair?

If both letters are the same (or only one letter is left), add an “X” after the first letter. Encrypt the new pair and continue. Some variants of Playfair use “Q” instead of “X”, but any letter, itself uncommon as a repeated pair, will do.

**What are the steps to encrypt a message using playfair cipher approach?**

Playfair Cipher Encryption Rules

- First, split the plaintext into digraphs (pair of two letters).
- After that, break the plaintext into digraphs (pair of two letters).
- To determine the cipher (encryption) text, first, build a 5*5 key-matrix or key-table and filled it with the letters of alphabets, as directed below:

**What will be the cipher text corresponding to plain text dollar if playfair cipher is used with keyword as secret assuming J is combined with i )?**

What will be the plain text corresponding to cipher text “BPKYFS” if playfair cipher is used with keyword as “SECRET” (assuming j is combined with i)? Clarification: To decrypt the message we follow the reverse procedure. Applying this we get the plain text to be “DOLLAR”.

### What are the various rules to encrypt the plaintext by using Playfair?

Step 1 – Creating the key square

H | E | L |
---|---|---|

R | D | A |

F | G | I |

N | P | Q |

U | V | X |

### What type of cipher is Playfair?

Playfair ciphers are a type of block cipher: the ciphertext character that replaces a particular plaintext character in the encryption will depend in part on an adjacent character in the plaintext.

**What are the steps to encrypt a message using Hill cipher approach?**

To encrypt a message, each block of n letters (considered as an n-component vector) is multiplied by an invertible n × n matrix, against modulus 26. To decrypt the message, each block is multiplied by the inverse of the matrix used for encryption.

**What is the rule for encryption in Playfair cipher if the letters in a pair are identical?**

What is the rule for encryption in playfair cipher if the letters in a pair are identical? Explanation: In playfair cipher if the letters in a pair are identical then a null is added in between the letters. Any letter can be used as a null as long as that letter is not the one being repeated.

#### What will be the size of a key matrix if the plain text is secret?

9. What will be the size of a key matrix if the plain text is “SECRET”? Explanation: Hill cipher uses a n x n matrix in order to cipher the plain text. In this case n=6 so a 6×6 matrix will be used.

#### Is Playfair cipher a block cipher?

Playfair ciphers are a type of block cipher: the ciphertext character that replaces a particular plaintext character in the encryption will depend in part on an adjacent character in the plaintext. Encryption is accomplished using a square array of characters, constructed from the encryption key.

**How secure is Hill cipher?**

The Hill cipher is a classical symmetric encryption algorithm that succumbs to the know-plaintext attack. Although its vulnerability to cryptanalysis has rendered it unusable in practice, it still serves an important pedagogical role in cryptology and linear algebra.