Wuxi MitraStar Technology Co. Ltd DSL100HNUT1V3 User Manual

Chapter 16    Certificates

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5 Additionally, Jenny uses her own private key to encrypt a message and Tim uses Jenny’s public key 

to decrypt the message.

The Device 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.

The certification authority uses its private key to sign certificates. Anyone can then use the 

certification authority’s public key to verify the certificates.

A certification path is the hierarchy of certification authority certificates that validate a certificate. 

The Device does not trust a certificate if any certificate on its path has expired or been revoked.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A directory of certificates that have been revoked before the scheduled expiration is called a CRL 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 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).

Certificates offer the following benefits.

• The 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.

The certification authority certificate that you want to import has to be in PEM (Base-64) encoded 

X.509 file format. This Privacy Enhanced Mail format uses 64 ASCII characters to convert a binary 

X.509 certificate into a printable form.

Before you import a trusted CA or trusted remote host certificate into the Device, you should verify 

that you have the actual certificate. This is especially true of trusted CA certificates since the Device 

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.