NETWORK SECURITY

1. PRESENTED BY
Name :S.PRAVEENA
Class : II-MSc CS
Batch : 2017 -2019
Incharge Staff : Ms. M. Florence Dayana

2. ROTOR MACHINCES
Each cylinder has 26 input pins and 26
output pins.

3.  The machine consist of a set of
independently rotating cylinder.
 we associate each input and output pin
with a letter of the alphabet, then a single
cylinder defines a monoalphabetic
substitution.
for example:
 An operate depresses the key for the
letter

5. The result is there are 26*26*26=17,576
Different substitution alphabets used before
the system repeats
setting o a5- rotor machine is equivalent to
a vigenere cipher with a key length of
11,881,376.
such a scheme presents a formidable
cryptanalytic challenge

6. STEGANOGRAPHY:

7.  A plaintext message may be hidden in one
of two ways.
 The method of steganography conceal the
Existence of the message.
 one that is time-consuming to construct
 The sequence of first letter of each word
the overall message spells out the hidden
message.

8. Character marking:
 b Selected letters of printed or typewritten
text are over written in pencil.
Invisible:
 A number of substances can be used for
writing but leave no visible trace until heat or
some chemical is applied to the paper

9. TRANSPOSITION TECHNIQUES
 A very different kind of mapping is
achieved by performing some sort of
permutation on the plaintext letter.
 The simplest such cipher is the rail
fence technique.
 meet me after the toga party with
Railway fence of depth2,we write the
following

10. for ex:
m e m a t r h t g p r y
e t e f e t e o a a t
The encrypted message is
MEMATRHTGPRYETEFETEOAAT

11. ROWS AND COLUMNS TRANSPOSITION

12. ONE TIME PAD:
 New message requires a new
key of the same length as the new message
 Such a scheme known as a
one-time-pad.
 it produces random output that
bears no statistical relationship to the
plaintext.
 Simply no way to break the code.

13. VERNAM CHIPHER:
 Vern am cipher is a
symmetrical stream cipher.
 The same length, to generate
the ciphertext,using the Boolean "exclusive
or”(XOR)function.
 The result will be a truly
random cipher text which bears no relation to
the original plaintext.

14. for ex:
 In the example below,we want to the
transmitted the word HELLO which is stored
on the plaintext tape.
 Incase the sequence AXHJB.

15. VERNAM CIPHER AUTOKEY SYSTEM:
In the illustration below,the
ciphertext tape is on the left`
It is XOR ad with a copy of the
original.
Key tape (AXHJB),resulting in the
original plaintext: "HELLO”.

16. For ex: