M.Sc Syllabus of Cyber Security, assignment on variety of Ciphers and Crypt analysis

2. PLAYFAIR
CIPHER

3. Hello!
I am AJAY KUMAR P
I am here because I love to give
presentations on PLAYFAIR
CIPHER .
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4. PLAYFAIR CIPHER
• The Playfair cipher was the first practical
digraph substitution cipher.
• The scheme was invented in 1854 by Charles
Wheatstone but was named after
• Lord Playfair who promoted the use of the
cipher.
• In playfair cipher unlike traditional cipher
• we encrypt a pair of alphabets(digraphs) instead
of a single alphabet.

5. ⬡ It was used for tactical purposes by British forces in
the Second Boer War and in World War I and for the
same purpose by the Australians during World War II.
⬡ This was because Playfair is reasonably fast to use and
requires no special equipment.
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6. BASIC CONCEPT
These concept bring the attention of
the words.
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The key table is a 5×5 grid of alphabets
that
acts as the key for encrypting the plaintext.
Each of the 25 alphabets must be unique
and one letter of the alphabet (usually J)
is omitted from the table as we need only
25 alphabets instead of 26. If the plaintext
contains J, then it is replaced by I.

7. Our process is easy:
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2
1 ENCRYPTION
DECRYPTION

8. Encryption
Generate the key
Square(5×5) at the
receiver's end: The key
square is a 5×5 grid of
alphabets that acts as
the key for encrypting
the plaintext. .
ENCRYPTION AND DECRPTION IN PLAYFAIR CIPHER
Decryption
Algorithm to decrypt the
cipher text: The cipher
text is split into pairs of
two letters
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9. 9
It was used for tactical purposes by British forces in the Second Boer
War and in World War I and for the same purpose by the
Australians during World War II
In playfair cipher unlike traditional cipher we encrypt a pair
of alphabets(digraphs) instead of a single alphabet
Where is Playfair cipher used?

10. The Playfair Cipher Encryption Algorithm:
The Algorithm consists of 2 steps:
⬡ Generate the key Square(5×5):
⬡ Algorithm to encrypt the plain text
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11. 11
1.Generate the key Square(5×5):
The key square is a 5×5 grid of alphabets that acts as the key for
encrypting the plaintext. Each of the 25 alphabets must be unique
and one letter of the alphabet (usually J) is omitted from the table
(as the table can hold only 25 alphabets). If the plaintext contains J,
then it is replaced by I.
The initial alphabets in the key square are the unique alphabets of
the key in the order in which they appear followed by the remaining
letters of the alphabet in order.

12. 2.Algorithm to encrypt the plain text:
The plaintext is split into pairs of two letters
(digraphs). If there is an odd number of letters, a Z is
added to the last letter.
For example:
Plaintext: "instruments"
After Split: 'in' 'st' 'ru' 'me' 'nt' 'sz'

13. 1. Pair cannot be made with same letter.
Break the letter in single and add a bogus
letter to the previous letter.
Plain Text: “hello”
After Split: ‘he’ ‘lx’ ‘lo’
Here ‘x’ is the bogus letter.
2. If the letter is standing alone in the process
of pairing, then add an extra bogus letter with
the alone letter
Plain Text: “helloe”
AfterSplit: ‘he’ ‘lx’ ‘lo’ ‘ez’
Here ‘z’ is the bogus letter.

14. Rules for Encryption:
If both the letters are in the same column:
Take the letter below each one (going back
to the top if at the bottom).
For example:
Diagraph: "me"
Encrypted Text: cl
Encryption:
m -> c
e -> l

15. 15
If both the letters are
in the same row: Take
the letter to the right of
each one (going back to
the leftmost if at the
rightmost position).
For example: Diagraph: "st"
Encrypted Text:tl
Encryption:
s -> t
t -> l

16. ⬡ If neither of the above rules is true: Form a
rectangle with the two letters and take the letters on
the horizontal opposite corner of the rectangle.
For example:
⬡ Diagraph: "nt"
⬡ Encrypted Text:rq
⬡ Encryption:
⬡ n -> r
⬡ t -> q
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17. For example:
Plain Text: "instrumentsz"Encrypted
Text:gatlmzclrqtxEncryption:i -> g
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n -> a
s -> t
t -> l
r -> m
u -> z
m -> c
e -> l
n -> r
t -> q
s -> t
z -> x

18. 18
Play fair cipher Screenshots

19. 19
Screenshots from online
As we refer in the online website
https://planetcalc.com/7751/

20. 20
Screenshot from online

21. In today's time, Playfair cipher is easily breakable by using
statistical or brute-force methods.
Why is it called Playfair cipher?
In 1854, Sir Charles Wheatstone invented the cipher
known as "Playfair," named for his friend Lyon Playfair,
first Baron Playfair of St. Andrews, who popularized and
promoted the cipher
Is Playfair cipher breakable?

22. Roadmap
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1 3 5
6
4
2
ENCRYPTED
MESSAGE PASSING MESSAGE PASSING MESSAGE PASSING
MESSAGE PASSING MESSAGE PASSING
success!
DECRYPTED
MESSAGE PASSING

23. 23
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z

24. 24
THANKYOU !

25. Presentation design
This presentation uses the following typographies:
⬡ Titles: TIMES NEW ROMAN
⬡ Body copy: TIMES NEW ROMAN
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26. Team Presentation
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AJAYKUMAR P
TITLE
PLAYFAIR CIPHER
HEMALATHA M
TITLE
PLAYFAIR CIPHER