11

Lesson 21Lesson 21

22

InternetInternet

Organization network

Organization network

Fire wall

33

Proxy ServerProxy Server

The Internet

The Internet

Proxy server

server

Client

Client

Client

Client

Hub

44

Computer Emergency Response Computer Emergency Response Team (CERT)Team (CERT)

Systems Administrator, Audit, Systems Administrator, Audit, Network and Security Institute (SANS Network and Security Institute (SANS Institute)Institute)

55

Transposition Transposition

I will not come today. Tell the boss.I will not come today. Tell the boss.

I W I L L

N O T C O

M E T O D

A Y . T E

L L T H E

B O S S

INMALBWOEYLOITT.TSLCOTHSLODEE

66

CryptographyCryptography Cryptography is a collection of mathematical techniques Cryptography is a collection of mathematical techniques

to ensure confidentiality of informationto ensure confidentiality of information Encryption and DecryptionEncryption and Decryption

The process of scrambling a message with the help The process of scrambling a message with the help of a key is called Encryptionof a key is called Encryption

The process of unscrambling a message using an The process of unscrambling a message using an appropriate key is called decryptionappropriate key is called decryption

Keys are numbers or characters that are randomly Keys are numbers or characters that are randomly generatedgenerated

Symmetric and Asymmetric cryptographySymmetric and Asymmetric cryptography Symmetric - same keys are used for encryption and Symmetric - same keys are used for encryption and

decryptiondecryption Asymmetric or Public Key Cryptography – a pair of Asymmetric or Public Key Cryptography – a pair of

public key and private key is used for encryption and public key and private key is used for encryption and decryptiondecryption

Pretty Good Privacy (PGP) is a popular cryptographic Pretty Good Privacy (PGP) is a popular cryptographic systemsystem

77

Digital/Electronic SignaturesDigital/Electronic Signatures An electronic signature means any An electronic signature means any

letters numbers, symbols, images, letters numbers, symbols, images, characters or any combination thereof characters or any combination thereof in electronic form applied to an in electronic form applied to an electronic documentelectronic document

An electronic signature ensures An electronic signature ensures AuthenticityAuthenticity IntegrityIntegrity Non- repudiation Non- repudiation