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C7200 VSA (VPN Services Adapter) Installation and Configuration Guide
OL-9129-02
Chapter 1 Overview
VSA Overview
• IKE—Internet Key Exchange (IKE) is a hybrid security protocol that implements Oakley and Skeme
key exchanges inside the Internet Security Association and Key Management Protocol (ISAKMP)
framework. IKE can be used with IPSec and other protocols. IKE authenticates the IPSec peers,
negotiates IPSec security associations, and establishes IPSec keys. IPSec can be configured with or
without IKE.
• CA—certification authority (CA) interoperability supports the IPSec standard, using Simple
Certificate Enrollment Protocol (SCEP) and Certificate Enrollment Protocol (CEP). CEP permits
Cisco IOS devices and CAs to communicate to permit your Cisco IOS device to obtain and use
digital certificates from the CA. IPSec can be configured with or without CA. The CA must be
properly configured to issue certificates. For more information, see the “Configuring Certification
Authority Interoperability” chapter of the Security Configuration Guide at
http://www.cisco.com/en/US/products/sw/iosswrel/products_ios_cisco_ios_software_releases.htm
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The component technologies implemented for IPSec include:
• DES and Triple DES—The Data Encryption Standard (DES) and Triple DES (3DES) encryption
packet data. Cisco IOS implements the 3-key Triple DES and DES-CBC with Explicit IV. Cipher
Block Chaining (CBC) requires an initialization vector (IV) to start encryption. The IV is explicitly
given in the IPSec packet.
• AES—The Advanced Encryption Standard, a next-generation symmetric encryption algorithm, used
by the U.S. Government and organizations outside the U.S.
• MD5 (HMAC variant)—MD5 is a hash algorithm. HMAC is a keyed hash variant used to
authenticate data.
• SHA (HMAC variant)—SHA is a hash algorithm. HMAC is a keyed hash variant used to
authenticate data.
• RSA signatures and RSA encrypted nonces—RSA is the public key cryptographic system developed
by Ron Rivest, Adi Shamir, and Leonard Adleman. RSA signatures provides non-repudiation while
RSA encrypted nonces provide repudiation.
IPSec with the Cisco IOS software supports the following additional standards:
• AH—Authentication Header is a security protocol that provides data authentication and optional
antireplay services.
The AH protocol uses various authentication algorithms; Cisco IOS software has implemented the
mandatory MD5 and SHA (HMAC variants) authentication algorithms. The AH protocol provides
antireplay services.
• ESP—Encapsulating Security Payload, a security protocol, provides data privacy services, optional
data authentication, and antireplay services. ESP encapsulates the data to be protected. The ESP
protocol uses various cipher algorithms and (optionally) various authentication algorithms. Cisco
IOS software implements the mandatory 56-bit DES-CBC with Explicit IV or Triple DES as the
encryption algorithm, and MD5 or SHA (HMAC variants) as the authentication algorithms. The
updated ESP protocol provides antireplay services.
VSA Overview
The C7200 VSA (VPN Services Adapter) is a full-width service adapter (see Figure 1-1) supported in the
I/O slot of the Cisco 7204VXR and Cisco 7206VXR routers with the NPE-G2 processor.