VPNs and VPN Technologies

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Jan 4, 2002.

Chapter Description

This sample chapter defines virtual private networks (VPNs) and explores fundamental Internet Protocol Security (IPSec) technologies. This chapter also covers IPSec crypto components, an overview of IKE, IPSec security, and a certificate authority (CA) support overview.

CA Support Overview

With a CA, you do not need to configure keys among all of the encrypting IPSec peers. Instead, you individually enroll each participating peer with the CA and request a certificate. When this has been accomplished, each participating peer can dynamically authenticate all of the other participating routers. To add a new IPSec peer to the network, you only need to configure that new peer to request a certificate from the CA, instead of making multiple key configurations with all the other existing IPSec peers.

This section presents an overview of how CA support works.

CA servers are responsible for managing certificate requests and issuing certificates to participating IPSec network devices. These services provide centralized key management for the participating devices. CAs simplify the administration of IPSec network devices so that IPSec keys do not have to be manually configured on each peer. You can use a CA with a network containing multiple IPSec-compliant devices, such as PIX Firewalls, Cisco routers, the Cisco VPN 3000 Concentrator series, the Cisco Secure VPN Client, and other vendors' IPSec products, as shown in Figure 1-24.

Figure 1-24 CA Support

Digital signatures, enabled by public key cryptography, provide a means to digitally authenticate devices and individual users. In public key cryptography, such as the RSA signature system, each user has a key pair containing both a public and a private key. The keys act as complements, and anything encrypted with one of the keys can be decrypted with the other. An RSA signature is formed when data is encrypted with a user's private key. The receiver verifies the signature by decrypting the message with the sender's public key.

The fact that the message could be decrypted using the sender's public key indicates that the holder of the private key—the sender—must have created the message. This process relies on the receiver having a copy of the sender's public key and knowing with a high degree of certainty that it really does belong to the sender, and not to someone pretending to be the sender.

A digital certificate contains information to identify a user or device, such as the name, serial number, company, department, or IP address. It also contains a copy of the entity's public key. A CA signs the certificate. The CA is a third party that is explicitly trusted by the receiver to validate identities and to create digital certificates.

To validate the CA's signature, the receiver must first know the CA's public key. Normally this is handled out-of-band or through an operation done at installation. For instance, most Web browsers are configured with the public keys of several CAs by default. The IKE, a key component of IPSec, can use digital signatures to authenticate peer devices before setting up SAs, while simultaneously providing scalability.

Without digital signatures, you must manually exchange either public keys or secret keys between each pair of devices that use IPSec to protect communications between them. Without certificates, every new device added to the network requires a configuration change on every other device with which it securely communicates. However, by using digital certificates, each device is enrolled with a CA. When two devices wish to communicate, they exchange certificates and digitally sign data to authenticate each other. When a new device is added to the network, one simply enrolls that device with a CA, and none of the other devices need modification. When the new device attempts an IPSec connection, certificates are automatically exchanged and the device can be authenticated. Without CA interoperability, devices could not use CAs when deploying IPSec. CAs provide a manageable, scaleable solution for IPSec networks.

Digital Signatures

The digital signature provides a form of digital credentials that authenticate the identity of the sending party, whoever that may be. In other words, digital signatures are used to link data with the holder of a specific private key and consist of the following:

  • At the local end, a private key is used to encrypt the hash.

  • At the remote end:

    • The hash is produced by running the original message through a algorithm.

    • The hash that was appended to the original message is decrypted using the sender's public key.

  • If the hashes match, the message is signed by a private key.

  • Only a specific private key could have produced the digital signature.

Figure 1-25 shows the digital signature process.

Figure 1-25 Digital Signatures

A key pair has no intrinsic ties to any person or entity. It could be sourced from Alice, Tom, or Harry Hacker masquerading as Alice or Tom. A solution is necessary to reliably tie a person or entity to a key pair. Digital signatures provide a way to "guarantee" the source of the message. The solution is digital signatures and digital certificates.

  • Digital signatures—Tie a message to a sender's private key. The hash can only be decrypted by the sender's public key.

  • Digital certificates—Bind a person or entity to a private key.

Certificate-Based Authentication

Digital certificates are used to authenticate users. They can be used to identify a person, a company, or a server. They are the equivalent of a digital passport or driver's license. The following example and Figure 1-26 illustrate how this works.

  Step 1 Users A and B register separately with the CA.
  • Digital certificates are issued by a trusted third party, a CA.
  • The CA issues separate certificates and digitally signs them with its private key, thereby certifying the authenticity of the user.
  Step 2 User A sends the certificate to User B.

  Step 3 User B checks the authenticity of the CA signature on the certificate.
  • The CA public key is used to verify the CA signature on the certificate.
  • If it passes validation, it is "safe" to assume User A is who he says he is, therefore the message is valid.
  Step 4 User B sends the certificate to User A.
  • The CA public key is used to verify the CA signature on the certificate.
  • Once verified, all subsequent communications can be accepted.

NOTE

Certificates are exchanged during the IPSec negotiations.

Figure 1-26 Certificate-Based Authentication

CAs

CAs hold the key to the public key infrastructure (PKI). A CA is a trusted third party whose job is to certify the authenticity of users to ensure that you are who you say you are.

Authenticity is guaranteed by the CA digital signature created with the CA private key. You can verify a digital signature using the CA public key. Only the CA public key can decrypt the digital certificate. The job of a CA is to

  • Create certificates
  • Administer certificates
  • Revoke invalid certificates

The CA can be a corporate network administrator or a recognized third party. Trusted sources supported by the Cisco VPN 3000 Concentrator Series include the following:

  • Entrust
  • GTE Cybertrust
  • Network Associates PGP
  • Baltimore
  • Microsoft
  • Verisign

Some CAs also use a Registration Authority (RA) to provide certificate enrollment services. An RA is server software that acts as a proxy for the CA, providing essential CA functions, such as certificate enrollment and distribution.

PKI

PKI is the set of hardware, software, people, policies, and procedures needed to create, manage, store, distribute, and revoke digital certificates. PKI makes it possible to generate and distribute keys within a secure domain and enables CAs to issue keys and associated certificate and certificate revocation lists (CRLs) in a secure manner. There are two PKI models, as shown in the following list and Figure 1-27.

  • Central authority

    • All certificates are signed by a single authority.

    • All certificates can be checked with that CA's public key.

  • Hierarchical authority

    • The ability to sign a certificate is delegated through a hierarchy. The top of the hierarchy is the root CA. It signs certificates for subordinate authorities.

    • Subordinate CAs sign certificates for lower-level CAs.

    • To validate a user's certificate, the certificate must be validated up through the chain of authority.

Figure 1-27 PKI

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children

This site is not directed to children under the age of 13.

Marketing

Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020