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22 votes
2 answers
14k views

What are the main weaknesses of a Playfair cipher, if any?

What are the main weaknesses of a Playfair cipher, if any? I know that they depend on none of the letters missing, but that is an easy fix if a letter gets dropped. Besides that, are there any other ...
Arlen Beiler's user avatar
11 votes
2 answers
18k 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 ...
GamingX's user avatar
  • 647
7 votes
3 answers
6k views

How to attack a classical cipher using known partial plaintext?

I have a ciphertext generated by a classical cipher. I do not know what was cipher used to generate it. I do however have the beginning of the plaintext. What are the cryptanalysis approaches for ...
Jake's user avatar
  • 71
7 votes
2 answers
8k 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, <...
helpneeded123's user avatar
5 votes
2 answers
32k 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: ...
Brian Brown's user avatar
4 votes
1 answer
1k 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 ...
user7538's user avatar
2 votes
1 answer
3k 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.
hperm's user avatar
  • 21
1 vote
1 answer
155 views

Can I use a Friedman test when decrypting a Playfair cipher?

I’d like to decrypt a Playfair ciphertext; however, I need to find the key word first. Is it possible to use the Friedman test here to find the length of the key word? My cipher has no J’s in it would ...
Lauren Hosking's user avatar
1 vote
1 answer
2k 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): ...
Grigory Zaripov's user avatar
0 votes
1 answer
1k 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 ... ...
Dawid Zbiński's user avatar
-2 votes
1 answer
547 views

Playfair cipher or ADFGX? [closed]

As part of an assignment, I have been given a cipher text of FFFXXXFGXAGFAFDAFXADDAGAD with the following description, ...
MPol's user avatar
  • 25