ZyXEL Communications 5 Series - Manual (Page 364)

ZyWALL 5/35/70 Series User’s Guide
364 Chapter 19 Certificates
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 A directory of certificates that have been revoked before the scheduled expiration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 ZyWALL 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).
19.1.1 Advantages of Certificates
Certificates offer the following benefits.
• The ZyWALL 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.
19.2 Self-signed Certificates
You can have the ZyWALL act as a certification authority and sign its own certificates.
19.3 Verifying a Certificate
Before you import a trusted CA or trusted remote host certificate into the ZyWALL, you
should verify that you have the actual certificate. This is especially true of trusted CA
certificates since the ZyWALL also trusts any valid certificate signed by any of the imported
trusted CA certificates.
19.3.1 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.
1 Browse to where you have the certificate saved on your computer.
2 Make sure that the certificate has a “.cer” or “.crt” file name extension.
Figure 191 Certificates on Your Computer
3 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.