ZyXEL NWA3000-N User Manual download pdf (Page 172)

Chapter 14 Certificates

NWA3000-N Series User’s Guide

172

This process works as follows:

1 Tim wants to send a message to Jenny. He needs her to be sure that it comes from

him, and that the message content has not been altered by anyone else along the

way. Tim generates a public key pair (one public key and one private key).

2 Tim keeps the private key and makes the public key openly available. This means

that anyone who receives a message seeming to come from Tim can read it and

verify whether it is really from him or not.

3 Tim uses his private key to sign the message and sends it to Jenny.

4 Jenny receives the message and uses Tim’s public key to verify it. Jenny knows

that the message is from Tim, and that although other people may have been able

to read the message, no-one can have altered it (because they cannot re-sign the

message with Tim’s private key).

5 Additionally, Jenny uses her own private key to sign a message and Tim uses

Jenny’s public key to verify the message.

The NWA3000-N series AP 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.

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 NWA3000-N series AP 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certificate on its path has expired or been revoked.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 A directory of certificates that have been revoked before the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 NWA3000-N

series AP 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 NWA3000-N series AP only has to store the certificates of the certification

authorities that you decide to trust, no matter how many devices you need to

authenticate.

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ZyXEL NWA3000-N User Manual Page 172