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Fundamentals of Cryptography and VPN Technologies
© 2012 Cisco and/or its affiliates. All rights reserved. 1
Contents
This chapter introduces the concepts of cryptography and VPN technologies. It covers the following topics:
• Need for VPN and VPN deployment models
• Encryption, hashing, and digital signatures and how they provide confidentiality, integrity, and nonrepudiation
• Methods, algorithms, and purposes of symmetric encryption
• Use and purpose of hashes and digital signatures in providing integrity and nonrepudiation
• Use and purpose of asymmetric encryption and Public Key Infrastructure (PKI)
© 2012 Cisco and/or its affiliates. All rights reserved. 2
VPN Overview
• Historically, a VPN was an IP tunnel.
• Therefore, a generic routing encapsulation (GRE) tunnel is technically a VPN, even though GRE does not encrypt.
• Today, the use of a VPN implies the use of encryption.
• With a VPN, the information from a private network is transported over a public network, such as the Internet, to form a virtual network instead of using a dedicated Layer 2 connection
© 2012 Cisco and/or its affiliates. All rights reserved. 3
Where VPNs Are Found
© 2012 Cisco and/or its affiliates. All rights reserved. 4
VPNs have many benefits
• Cost savings
• Scalability
• Compatibility with broadband technology
• Security
© 2012 Cisco and/or its affiliates. All rights reserved. 5
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