Network security cryptography ppt

NETWORK NETWORK SECURITY SECURITY

CRYPTOGRAPHYCRYPTOGRAPHY

BY:R.Thushara Bharathi (CSE)

S. Jahnavi (CSE)

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.

WHAT IS NETWORK

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.

NETWORK SECURITY

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.

PROBLEMS & ATTACKS

It is derived from the Greek word that meant for secret writing.

Cryptography is the ability to send information between particulars in a way that it prevents others from reading the data.

The data is transferred by applying two techniques by changing the plain text & Cipher texts as Encryption (P to C) & Decryption (C to P).

CRYPTOGRAPHY

The two fundamental principles of cryptography are: Messages must contain some Redundancy (information

not needed to understand the message). Some method is needed to foil replay attacks (validation

of messages by timestamp) i.e. freshness. The services provided by the cryptography are as follows:

Integrity Checking Authentication Protection to the data Confidentiality of information etc.

PRINCIPLES & SERVICES OF CRYPTOGRAPHY

ENCRYPTION & DECRYPTION

The way of converting the plain text to the cipher text by the means of few keys is called as “encryption”.

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”.

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 Digrams Trigrams

SUBSTITUTION 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”.

TRANSPOSITION CIPHER

The implementation of a simple cryptography using single key is done by the secret-key algorithms.

This can be done by p-box, s-box and product cipher.

SECRET-KEY ALGORITHMS

ELEMENTS OF PRODUCT CIPHERS

Transpositions & substitutions can be done through p-box (a).

Substitutions can be done through s-box (b). Mapping of the p-box with s-boxes form product

cipher (c).

Public key algorithms are formed when it satisfies the following requirements: D(E(P))=P. Difficulty to deduce D

from E. E cannot be broken

by a chosen plain text attack.

PUBLIC-KEY ALGORITHMS

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.

But takes much time for the large volumes of data encryption. This is done by few mathematical principles as: Choose 2 large primes. Compute n=pxq & z=(p-1)x(q-1). Find e, exd=1 mod z.

RSA ALGORITHM

Advantages : Used to protect the data from the others. Used to send the data / packet in a secured way

from the source to destination. Avoids in knowing the data in the way of

sending. Disadvantages:

Hacking is done now-a-days easily even for the data encrypted with 48 bits though the bits are extended by 52-bits.

ADVANTAGES & DISADVANTAGES

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.

PROPOSED CONCEPT