ZyXEL Communications NBG410W3G Series User Manual

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Chapter 11 Certificates
NBG410W3G Series User’s Guide
196
Certification authorities maintain directory servers with databases of valid and revoked 
certificates. A directory of certificates that have been revoked before the scheduled expiration 
is called a CRL (Certificate Revocation List). The ZyXEL Device can check a peer’s 
certificate against a directory server’s list of revoked certificates. The framework of servers, 
software, procedures and policies that handles keys is called PKI (public-key infrastructure).
11.1.1  Advantages of Certificates
Certificates offer the following benefits.
• The ZyXEL Device only has to store the certificates of the certification authorities that 
you decide to trust, no matter how many devices you need to authenticate. 
• Key distribution is simple and very secure since you can freely distribute public keys and 
you never need to transmit private keys.
11.2  Self-signed Certificates
You can have the ZyXEL Device act as a certification authority and sign its own certificates.
11.3  Verifying a Certificate
Before you import a trusted CA or trusted remote host certificate into the ZyXEL Device, you 
should verify that you have the actual certificate. This is especially true of trusted CA 
certificates since the ZyXEL Device also trusts any valid certificate signed by any of the 
imported trusted CA certificates.
11.3.1  Checking the Fingerprint of a Certificate on Your Computer
A certificate’s fingerprints are message digests calculated using the MD5 or SHA1 algorithms. 
The following procedure describes how to check a certificate’s fingerprint to verify that you 
have the actual certificate. 
Browse to where you have the certificate saved on your computer. 
Make sure that the certificate has a “.cer” or “.crt” file name extension.
Figure 118   Certificates on Your Computer
Double-click the certificate’s icon to open the Certificate window. Click the Details tab 
and scroll down to the Thumbprint Algorithm and Thumbprint fields.