cisco securit y

© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—1-1

Cisco Security


An Example

=> How to transport the letter safely ?

=> Worry somebody intercept the letter ?

=> Worry somebody falsify the letter ?

=> Worry writter or transporter negative the letter ?


Security Meaning

=> Ensure the source

=> Ensure the message could not be falsify or intercept

while transportion

=> Ensure the message could not be cracked

=> No negation


Basics of Encryption

There are two types of encryption keys:

=> Symmetric

=> Asymmetric


Symmetric

With symmetric key encryption, each peer uses the same

key to encrypt and decrypt the data.


Symmetric Encryption


Maybe Perfect


An Obvious Problerm

=> How to send the "key" ?

=> QQ ? MSN ? E-mail ? Telephone ?

=> Bike ? Bus ? Train ? Airplane ?


Asymmetric

With asymmetric key encryption, the local end uses one

key to encrypt,and the remote end uses another key to

decrypt the traffic.


Asymmetric Encryption


Maybe Perfect


An Obvious Problem

=> Cracker will exchange the letter . How to solve this

problerm ?


A perfect Encryption


A Perfect Decryption

cisco securit y

Documents