This chapter introduces the concepts of cryptography and covers encryption, hashing, and digital signatures and how these techniques provide confidentiality, integrity, authenticity, and nonrepudiation. You will learn about algorithms, symmetric and asymmetric encryption, digital signatures, and Public Key Infrastructure (PKI). | Fundamentals of Cryptography and VPN Technologies 1 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) Contents 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 VPN Overview Where VPNs Are Found 4 • Cost savings • | Fundamentals of Cryptography and VPN Technologies 1 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) Contents 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 VPN Overview Where VPNs Are Found 4 • Cost savings • Scalability • Compatibility with broadband technology • Security VPNs have many benefits There are different types of commercially deployed VPNs. VPN are classified according to the following criteria: • Based on deployment mode: Site-to-site VPN and remote-access VPN • Based on Open Systems Interconnection (OSI) layer: Layer 2 VPN (legacy protocols such as Frame Relay or ATM, and Layer 2 MPLS VPN), Layer 3 VPN (IPsec and MPLS Layer 3 VPN), and Layer 7 VPN (SSL VPN) • Based on underlying technology: IPsec VPN, SSL VPN, MPLS VPN, other Layer 2 technologies such as Frame Relay or ATM, and hybrid VPNs combining multiple technologies VPN Types Cisco VPN Solutions Site-to-Site VPNs Remote-Access VPNs Cryptographic services are the foundation for many security implementations. The key services provided by cryptography are as follows: • Confidentiality: The assurance that no one can read a particular piece of data except the receivers explicitly intended. • Integrity or data authentication: .
