# Questions tagged [playfair]

The Playfair cipher is a digraph substitution cipher. It employs a table where one letter of the alphabet is omitted, and the letters are arranged in a 5x5 grid.

22 questions
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### Playfair cipher - questions about inserting 'X'

I'm implementing the Playfair cipher as part of a programming project. I realize there are different versions of the cipher - I've been asked to implement the version which treats the letters 'I' and '...
592 views

### Cracking transposition cipher

I have a task to decrypt custom made transposition cipher, as I'm not the cryptography expert, I would appreciate any help. I've been given the table of characters ... ...
606 views

### How large is the Playfair cipher keyspace? [duplicate]

In the Playfair cipher, is the key space 5 x 5 = 25 or 25 x 25 = 625? I'm trying to work out the size of the key space if each set of equivalent keys is counted as one key.
273 views

### Substitution Cipher Help: Can't figure out keyword [closed]

Given a keyword, you can encrypt a message using alphabetical substitution like this: ...
183 views

### Unknown Encryption Method

As part of an assignment, I have been given a cipher text of FFFXXXFGXAGFAFDAFXADDAGAD with the following description, ...
698 views

### How to decode a Playfair message with a partial key?

I've been given a Playfair ciphered message and a partial key, where a few key letters are missing: Corrupted key (? stands for a missing letter): ...
15k views

### How to find the keyword of the Playfair cipher, given the plaintext and the ciphertext?

I know how the Playfair cipher works. I would like to know how to find the keyword of the Playfair cipher, given some ciphertext and the corresponding plaintext. For example: encrypted: ...
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### Decoding the Playfair cipher with a crib [duplicate]

I have a Playfair cipher text and I know a portion of the text (one world). How can I decode the cipher from here? Thanks.
241 views

### Unicity-distance of Playfair

Given the classical scheme Playfair, say, for 5*5 matrices, I am interested to determine its unicity-distance. How should one proceed to properly do that? I should appreciate it, if I could obtain a ...
99 views

### Playfair Cipher Confusion with one column encryption

Recently I decided to learn "Playfair Cipher", and I have hit a road block. what do i substitute the letters for if they are on the same column? Here is an example: ...
121 views

### How to create and validate potential grids when attacking a Playfair cipher?

First up: I am not asking you to decypher anything. This question is about attacking a Playfair cipher; more specifically – how to create potential grids when doing so. I'm currently working on a ...
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### Does the length of the keyword used for keytable for Playfair matter?

So for Playfair, we choose a keyword and put that in the keytable with no duplicates. Then, we fill the rest of the table with alphabets in order that are not in the keyword without 'J'. Does the ...
1k views

### Playfair Cipher + Vigenere Cipher?

I'm researching cryptography for a school project, came across the above two ciphers, and something occurred to me. Would combining these two schemes give a considerably stronger encryption than ...
275 views

### encryption of message “DATACONFANTIALITY” with key playfair using playfair cipher

actually i have solved the above mentioned problem but i want to check weather it is correct or not. my question is that how to encrypt the message DATACONFANTIALITY using the playfair cipher where ...
5k views

### How does cryptanalysis of the Playfair cipher work?

I have a set of Playfair-enciphered data that I'm trying to crack without the key. I know I need to analyse bigrams; I've currently worked out what decrypts to th, <...
359 views

### Multi-round Transposition/Playfair as a secure hand cipher in the computer age [closed]

Given that computers can be easily compromised, there is a need for a hand cipher that can withstand computer attack. Clearly the traditional hand ciphers fail. One time pads work. They also have ...
578 views

### Encryption of numeric value using playfair

I am studying in CSE and in my recent exam paper, A question was asked as: Construct a playfair cipher for Plaintext: semester5 and key:technology. Generally as we are taught yet, there is no ...
2k views

### Number of possible keys in a Play fair cipher [duplicate]

So for the play fair case, the number of possible keys is : 26x26 = 676 possible keys But if we consider the repeated letters, how many unique keys will the play fair have? I mean how will ...
881 views

### Four-Square cipher and its keyspace

Am I thinking about this correctly? Consider that the keyspace of the Playfair cipher is equivalent to all permutations of the alphabet, e.g. the number of distinct permutations of 25 objects, and ...
8k views

### How many keys does the Playfair Cipher have?

I was just studying the Playfair cipher and from what I've understood, it is just a slightly better version of a Caesar cipher, in that it isn't actually mono-alphabetic but rather the 'digrams' are ...