Network Security & Cryptography

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Cryptography: An Innovative Technique for Information

Security

HIMANSHU GUPTA, FACULTY MEMBER, AMITY UNIVERSITY

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Security Attacks

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Security Attacks

Informationsource

Informationdestination

Normal Flow

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Security Attacks

Informationsource

Informationdestination

Interruption

• Attack on availability

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Security Attacks

Informationsource

Informationdestination

Interception

• Attack on confidentiality

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Security Attacks

Informationsource

Informationdestination

Modification

• Attack on integrity

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Security Attacks

Informationsource

Informationdestination

Fabrication

• Attack on authenticity

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Classify Security Attacks

passive attacks - eavesdropping on, or monitoring of, transmissions to:

obtain message contents, ormonitor traffic flows

active attacks – modification of data stream to:

masquerade of one entity as some otherreplay previous messagesmodify messages in transitdenial of service

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Security Attacks

Release of message contents

Trafficanalysis

• eavesdropping, monitoring transmissions

Passive threats

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Passive Attacks

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Security Attacks

Masquerade Denial ofservice

• some modification of the data stream

Active threats

Replay Modification of message contents

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Active Attacks

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Security Services

Confidentiality – protection from passive attacks

Authentication – you are who you say you are

Integrity – received as sent, no modifications, insertions, shuffling or replays

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Security Services

Nonrepudiation – can’t deny a message was sent or received

Access Control – ability to limit and control access to host systems and apps

Availability – attacks affecting loss or reduction on availability

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Network Security Model

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Cryptography

Cryptography -- from the Greek for “secret writing” -- is the mathematical “scrambling” of data so that only someone with the necessary key can “unscramble” it.

Cryptography allows secure transmission of private information over insecure channels (for example packet-switched networks).

Cryptography also allows secure storage of sensitive data on any computer.

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The language of cryptography

symmetric key crypto: sender, receiver keys identicalpublic-key crypto: encryption key public, decryption

key secret (private)

plaintext plaintextciphertext

KA

encryptionalgorithm

decryption algorithm

KB

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Public-Private key Cryptography

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Secret/Symmetric-key Cryptography

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Secure Communication over Insecure Medium

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RSA Encryption Algorithm

For example. make p = 7and q = 13

We then calculate N = 7∗13 = 91 and (p−1)(q−1) = 72

We next select ke relatively prime to 72 and< 72, yielding 5

Finally,we calculate kd such that ke*kd mod 72 = 1, yielding 29

We how have our keys

Public key, ke, N = 5, 91

Private key, kd , N = 29, 91

Encrypting the message 69 with the public key results in the cyphertext 62

Cyphertext can be decoded with the private key

Public key can be distributed in cleartext to anyone who wants to communicate with holder of public key

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Encryption and Decryption using RSA Asymmetric Cryptography

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What is a Firewall?

a choke point of control and monitoring interconnects networks with differing trustimposes restrictions on network services

only authorized traffic is allowed

auditing and controlling accesscan implement alarms for abnormal behavior

is itself immune to penetrationprovides perimeter defence

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Firewall: Technical Concept

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Firewall ConfigurationsFirewall Configurations

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Thank You!!!!

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Have A Nice Week!!!