Cisco Securit y
description
Transcript of Cisco Securit y
© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—1-1
Cisco Security
© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—1-2
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 ?
© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—1-3
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
© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—1-4
Basics of Encryption
There are two types of encryption keys:
=> Symmetric
=> Asymmetric
© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—1-5
Symmetric
With symmetric key encryption, each peer uses the same
key to encrypt and decrypt the data.
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Symmetric Encryption
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Maybe Perfect
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An Obvious Problerm
=> How to send the "key" ?
=> QQ ? MSN ? E-mail ? Telephone ?
=> Bike ? Bus ? Train ? Airplane ?
© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—1-9
Asymmetric
With asymmetric key encryption, the local end uses one
key to encrypt,and the remote end uses another key to
decrypt the traffic.
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Asymmetric Encryption
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Maybe Perfect
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An Obvious Problem
=> Cracker will exchange the letter . How to solve this
problerm ?
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A perfect Encryption
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A Perfect Decryption
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