The art of protecting information by transforming it (or encrypting) it into an unreadable format, called cipher text. Only those who possess a secret key can decipher (or decrypt) the message into plain text. It provides Confidentiality, Integrity, Accuracy.

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CRYPTOGRAPHY
“KRYPTOS” “GRAPHEIN”
which means Which means
“Hidden Secrets” “ writing”
“secret writing”
Is derived
from a Greek
word
That
means

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 The art of protecting
information by transforming
it (or encrypting) it into an
unreadable format, called
cipher text. Only those who
possess a secret key can
decipher (or decrypt) the
message into plain text.
 It provides Confidentiality,
Integrity, Accuracy.

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Plain Text - HELLO
Cipher Text - IFMMP
The Output Message-HELLO
After encryption process
Decrypted message
By using any one of the cipher

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Plain Text - HELLO
Cipher Text - IFMMP
COVER IMAGE
After encryption process

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THE ENCRYPTED FORM
AFTER DECRYPTION PROCESS
Message- HELLO
AND
COVER IMAGE

7. Encryption -
•The process that converts original information,
also called plain text into a difficult-to-interpret
form called cipher text .
Decryption -
•The process of converting cipher text into a
plain text is called Decryption.
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8. Cryptography
Symmetric key Asymmetric key
cryptography cryptography
(Public key cryptography)
Classical Modern
cryptography cryptography
Transposition Substitution caesar Block
cipher cipher cipher cipher
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10. SYMMETRIC KEY CRYPTOGRAPHY
TECHNIQUE
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Sender receiver
sender’s
Encryption
Key K
receiver’s
Decryption
Key K
Plaintext Plaintext
Ciphertext within
an image
If m = Plaintext and K is the shared secret key,
then
• Ciphertext = K(m) and
• m = K(K(m))
Shared
Secret
Key K

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12. ASYMMETRIC KEY
CRYPTOGRAPHY TECHNIQUE
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sender receiver
3rd person
Plaintext Plaintext
Ciphertext within
an image
sender’s
Encryption
Key K1
Receiver’s
Decryption
Key K2
If m = Plaintext, then
• Ciphertext = K1(m) and
• m = K2(K1(m))

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 Plaintext-
Data that can be read
and understood without
any special measures.
 Key-
some secret piece of
information that
customizes how the
cipher text is produced
 Cipher text-
Encrypting plaintext
results in unreadable
gibberish called cipher
text.
 Cipher -
Pair of algorithms
performing encryption
& decryption.

14. MATLAB
 Matlab is basically a high level language which has many
specialized toolboxes for making things easier for us.
 Matlab is too broad for our purposes in this course.
 The features we are going to require is-
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Matlab
Command
Line
m-files
functions
mat-files
Command execution
like DOS command
window
Series of
Matlab
commands
Input
Output
capability
Data
storage/
loading

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MATLAB SCREEN
•Command Window
-type commands
•Current Directory
-View folders and m-files
•Workspace
-View program variables
-Double click on a variable
to see it in the Array Editor
•Command History
-view past commands
-save a whole session
using diary

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• RSA is a cryptosystem for public-key encryption, and is widely used for
securing sensitive data, particularly when being sent over an insecure
network such as the Internet.
• RSA was first described in 1977 by Ron Rivest, Adi Shamir and
Leonard Adleman of the Massachusetts Institute of Technology.
• In RSA cryptography, both the public and the private keys can encrypt a
message; the opposite key from the one used to encrypt a message is
used to decrypt it. This attribute is one reason why RSA has become the
most widely used asymmetric algorithm.
•It provides a method of assuring the confidentiality, integrity, authenticity
and non-reputability of electronic communications and data storage.

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