This document discusses the Caesar cipher and Hill cipher methods of encryption. It provides an introduction to each cipher, including how the Caesar cipher works by shifting letters of the alphabet and how the Hill cipher uses a matrix to encrypt blocks of text. The key advantages and disadvantages of each cipher are outlined, such as the Caesar cipher being very easy to implement but also easy to hack, while the Hill cipher provides more security but encrypted text cannot be decrypted if the key matrix is noninvertible. Examples of encrypting and decrypting text using each cipher are also included.

1. Name: Md Fazle Rabbi
ID:16CSE057
Ceaser and Hill cipher

2. CONTENTS
 Introduction of Caesar cipher
 Applying technique of Caesar cipher
 Caesar cipher example
 Advantages of Caesar cipher
 Disadvantages of Caesar cipher
 Introduction of Hill cipher
 Disadvantages of Hill cipher
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3. INTRODUCTION OF CAESAR CIPHER
 The Caesar cipher is one of the earliest known and
simplest ciphers. It is a type of substitution cipher in
which each letter in the plaintext is 'shifted' a
certain number of places down the alphabet.
 For example, with a shift of 1, A would be replaced
by B, B would become C, and so on. The method is
named after Julius Caesar, who apparently used it
to communicate with his generals.
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4. APPLYING TECHNIQUE OF CAESAR CIPHER
 Encryption
 We apply encryption formulas by character, based on
alphabetical order.
 The formula of encryption is:
 Decryption
 We apply decryption formulas by character, based on
alphabetical order.
 The formula of decryption is:
Where,
E denotes the encryption
D denotes the decryption
p denotes the letters value
k denotes the key value (shift value)
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5. SHIFTING TECHNIQUE OF CAESAR CIPHER
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6. ENCRYPTION CAESAR CIPHER
The encrypted message of this plain text is "WTAAD".
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The plain text is “HELLO".

7. DECRYPTION CAESAR CIPHER
The decrypted message is "HELLO".
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The encrypted message of this plain text is "WTAAD".

8. ADVANTAGES OF CAESAR CIPHER
 It is very easy to implement.
 This method is the simplest method of
cryptography.
 Only one short key is used in its entire process.
 If a system does not use complex coding
techniques, it is the best method for it.
 It requires only a few computing resources.
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9. DISADVANTAGES OF CAESAR CIPHER ARE AS
FOLLOWS: -
 It can be easily hacked. It means the message
encrypted by this method can be easily decrypted.
 It provides very little security.
 By looking at the pattern of letters in it, the entire
message can be decrypted.
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10. WHAT IS HILL CIPHER?
 Hill cipher is a polygraphic substitution cipher
based on linear algebra.
 Each letter is represented by a number modulo 26.
 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
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11. HILL CIPHER ENCRYPTION EXAMPLE
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HELLO WORLD
SLHZY ATGZT

12. HILL CIPHER DECRYPTION EXAMPLE
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HELLO WORLD
SLHZY ATGZT

13. DISADVANTAGE OF HILL CIPHER
 Noninvertible key matrix over is the
main disadvantage of Hill Cipher, because few of
the matrices have inverses over . This means that
the encrypted text can't be decrypted.
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14. THE END