ZyXEL Communications P-792H - Certificates Technical Reference; Certificates Overview; Private-Public Certificates

Chapter 11 Certificates
P-792H v2 User’s Guide
152
11.3 Certificates Technical Reference
This section provides technical background information about the topics covered in
this chapter.
11.3.1 Certificates Overview
The P-792H v2 can use certificates (also called digital IDs) to authenticate users.
Certificates are based on public-private key pairs. A certificate contains the
certificate owner’s identity and public key. Certificates provide a way to exchange
public keys for use in authentication.
The P-792H v2 uses certificates based on public-key cryptology to authenticate
users attempting to establish a connection, not to encrypt the data that you send
after establishing 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.
Advantages of Certificates
Certificates offer the following benefits.
• The P-792H v2 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.
11.3.2 Private-Public Certificates
When using public-key cryptology for authentication, each host has two keys. One
key is public and can be made openly available. The other key is private and must
be kept secure.
These keys work like a handwritten signature (in fact, certificates are often
referred to as “digital signatures”). Only you can write your signature exactly as it
should look. When people know what your signature looks like, they can verify
whether something was signed by you, or by someone else. In the same way, your
private key “writes” your digital signature and your public key allows people to
verify whether data was signed by you, or by someone else. This process works as
follows.