ZyXEL ZyWALL USG 50 User Manual - Page 633

CHAPTER 41 Certificates 41.1 Overview The ZyWALL 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. 41.1.1 What You Can Do in this Chapter • Use the My Certificate screens (see Section 41.2 on page 637 to Section 41.2.3 on page 646) to generate and export self-signed certificates or certification requests and import the ZyWALL's CA-signed certificates. • Use the Trusted Certificates screens (see Section 41.3 on page 647 to Section 41.3.2 on page 652) to save CA certificates and trusted remote host certificates to the ZyWALL. The ZyWALL trusts any valid certificate that you have imported as a trusted certificate. It also trusts any valid certificate signed by any of the certificates that you have imported as a trusted certificate. 41.1.2 What You Need to Know 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. 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). ZyWALL USG 50 User's Guide 633