This document discusses network security and cryptography. It begins by defining a network and some common network threats. It then discusses network security goals like avoiding denial of service attacks. The document outlines different cryptography techniques like symmetric and asymmetric key cryptography. Symmetric cryptography uses a shared key while asymmetric uses public and private keys. Specific algorithms like RSA and DES are described. The document proposes combining numerals and alphabets in encryption to increase security. It concludes cryptography can securely hide and transmit data through encryption and decryption.

1. NETWORK SECURITY
CRYPTOGRAPHY
Presented BY
Sankari.P(B.Sc[CS] S/F)
Sadakathullah Appa College
Tirunelveli -11.
Guided by:
Mrs.J .Jannathul Firthous ,M.sc,M.phil

2. WHAT IS NETWORK
 A network is an interconnection
or a media between two or more
systems to share information
among them.
 The various threats caused to
network are :
 Remote Login
 Application Backdoors
 SMTP Session Hijackings
 Operating System Bugs
 Spams
 Viruses etc.

3. NETWORK SECURITY
 The security provided to the network
is called network security which at
present is looming on horizon as a
massive problem.
There are two kinds of Network
Security mainly as :
 Transit Security: It just encrypts
the packets to be transferred.
 Traffic Security : It acts just as a
screen between hosts & remote
sites.

4. SECURITY GOALS

5. OBJECTIVE OF SECURITY
 To avoid data threats
 To avoid denial of services
 To secure our data from masquerades
 To safeguard our data’s from traffic analyzer
 To not to make massage for the third person available

6. PASSWORD AUDITING
 Should not be in uppercase
 Must have at least 8 characters
 Must include alphabets, numeric keys & special
characters
 Password should not be the name of the user,
dictionary word etc.,
 It must be updated at least once a month

7. DATA SECURITY
 To monitor the user’s ACCESS
CONTROLS
 System that are connected in network must be protected
with firewalls
To protect the integrity & availability of the institution’s
information asset’s

8. PROBLEMS & ATTACKS
There are few intertwined areas in network security as:
 Secrecy
 Authentication
 Non-Repudiation
 Integrity Control etc.
The threats are classified into two categories :
Passive Attacks :
A passive attack is one in which the attacker eavesdrops and
listens to the message but can’t modify the message.
Active Attacks :
An active attack is one in which the attacker modifies, deletes,
replay or introduce new messages into the stream of message.

9. THREATS :

10. CLICK

11. CRYPTOGRAPHY
 It is derived from the Greek word that meant for secret writing.
 Cryptography is a Software or Hardware programs
use Mathematical Functions , Formulas(Algorithms) to
change text from one form to another.
 Cryptography is the science and art of transforming messages to
make them secure and immune to attacks.
 It provides Confidentiality, Integrity, Accuracy.
 Applications of cryptography includes ATM cards, computer
passwords, and electronic commerce.
 It’s very useful to our Army & Police network to transfer
confidential data

12. TECHNIQUES
The data is transferred by applying two techniques
1.Encryption
2.Decryption
Encryption :The way of converting the plain text to the
cipher text by the means of few keys is called as the
“Encryption”.
Decryption :The way of converting the cipher text to
the plain text by the use of keys that are suitable to it is
called as “Decryption”.

13. ENCRYTION & DECRYPTION

14. CATEGORIES OF CRYPTOGRAPHY

15. SYMMETRIC KEY CRYPTOGRAPHY
 The implementation of a simple cryptography using
single key is done by the secret-key algorithms.
 Also known as SECRET KEY CRYPTOGRAPHY .
Sender & Receiver uses same key and an Encryption /
Decryption Algorithm to Encrypt / Decrypt data .
(i.e ) The Key is Shared
 This can be done by p-box, s-box and product cipher

16. SYMMETRIC KEY CRYPTOGRAPHY

18. SUBSTITUTION CIPHER
Replacing of each letter or
group of letters of plain text
into cipher text by another
letters is called as
“Substitution cipher”.
The substitution may be :
Monoalphabetic Substitution
Polyalphabetic Substitution

19. TRANSPOSITION CIPHER
 The change offered in
the position of the text
i.e. By jumbling the
words is called as
“Transposition cipher”.
 And the technique used
here is termed as “Mass
Technique”.

20. ASYMMETRIC KEY CRYPTOGRAPHY
 Also known as PUBLIC KEY CRYPTOGRAPHY . Sender &
Receiver uses different keys for Encryption & Decryption
namely PUBLIC & PRIVATE respectively
 Public key algorithms are formed when it satisfies the
following requirements:
o D(E(P))=P.
o Difficulty to deduce D from E.
o E cannot be broken by a chosen plain text attack.
D -> Deciphering E -> Enciphering

21. ASYMMETRIC KEY CRYPTOGRAPHY

22. RSA ALGORITHM
 RSA is derived from the names of the 3 discoverers
named Rivest, Shamir, Adleman.
 The RSA algorithm is one of the widely used in the key
algorithms.
(1)The main function of this algorithm is providing
approach to public key cryptography & Encryption
(2) In this the CIPHER TEXT are the integer’s
between 0 to n-1
C =e M mod n m->message ,e->encryption
M=d C mod n C->cipher text ,d->decryption
=(e M) d mod n n-> integer’s (r*a) r & a are prime
=m e d mod n number’s

24. Symmetric key
cryptography
• Only 1 shared key is involved.
• The same key encrypts and
decrypts the plaintext.
• The shared key is kept secret
between Alice and Bob.
• Examples of Symmetric
algorithms:
– DES, 3DES, AES, IDEA,
BLOWFISH, TWOFISH, RC4,
RC5, SAFER etc.
Asymmetric key
cryptography
• Here 2 keys : a private and a
public key are involved.
• The Public key encrypts the
plaintext while the private key
decrypts it.
• The private key is just kept
secret by the Bob while the
public key is made public.
• Examples of Asymmetric
algorithms:
– Diffie-Hellman, RSA, El Gamal,
Elliptic Curve Cryptography
(ECC) etc.

25. APPLICATIONS
• Defense Services
• Secure Data Manipulation
• E – Commerce
• Business Transactions
• Internet Payment Systems
• User Identification Systems
• Access Control
• Data Security

26. PROPOSED CONCEPT
 As known the data has been easily hacked
even for the 52- bit encryption too. So, the
encryption bits of 52-bits should be given
with the combination of both numerals and
alphabets ( for example one alphabet is
placed for 13-bits each).
 The placement of alphabet is known only to
the particular sender & receiver such that it
secures the data to be sent.

27. CONLUSION
 This paper describes a technique to successfully
hiding and secure the data or massage with the
help of Encryption or Decryption technique with
the Cryptography And Network Security.
 However ,this research work & software package
provide a good starting point for anyone
interested in learning about Cryptography.

28. “For every lock there is a key………
It is better to keep safe your lock than the key”