ZyXEL Communications 5 Series User Manual
Chapter 20 Certificates
ZyWALL 5/35/70 Series User’s Guide
400
The ZyWALL uses certificates based on public-key cryptology to authenticate users
attempting to establish a connection. The method used to secure the data that you send through
an established connection depends on the type of connection. For example, a VPN tunnel
might use the triple DES encryption algorithm.
attempting to establish a connection. The method used to secure the data that you send through
an established connection depends on the type of connection. For example, a VPN tunnel
might use the triple DES encryption algorithm.
The certification authority uses its private key to sign certificates. Anyone can then use the
certification authority’s public key to verify the certificates.
certification authority’s public key to verify the certificates.
A certification path is the hierarchy of certification authority certificates that validate a
certificate. The ZyWALL does not trust a certificate if any certificate on its path has expired or
been revoked.
certificate. The ZyWALL does not trust a certificate if any certificate on its path has expired or
been revoked.
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 A directory of certificates that have been revoked before the scheduled expiration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).
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 A directory of certificates that have been revoked before the scheduled expiration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).
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.
Self-signed Certificates
You can have the ZyWALL act as a certification authority and sign its own certificates.
20.1.3 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.
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.
You can use a certificate’s fingerprint to verify it. A certificate’s fingerprint is a message
digest 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.
digest 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.
2 Make sure that the certificate has a “.cer” or “.crt” file name extension.
Figure 232 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.