Title: SSL Certificates
Course: CIS 208: Linux/UNIX III: Intermediate System Administration, Networking, and Security ~ For IGNITE Review > Section: Learning Modules

SSL Certificates

SSL certificates can be used to provide encryption of data as it passes through a network, however they provide an even more basic function.  Certificates are used to verify that connections are made to the right server and not to an impersonator.  This authentication only occurs when a certificate has been created by a Certificate Authority (CA) and the client trusts that particular CA.  The client stores a certificate for the CA and this certificate is used to verify the certificates on websites.

For convenience, most web browsers include a set of well-known CA certificates. These are managed by organizations that verify companies before issuing certificates. This prevents an impersonator from buying a certificate for an organization which they do not represent.  Web browsers will show that there is an SSL connection when viewing a supported website.

It is possible for anyone to create a CA.  This can be convenient for internal use by a company or for testing.  Any clients would need to load the "self-signed" certificate for the CA and connections will work properly.  Just as websites can get a certificate from a well-known CA, so can custom CAs.  A CA which is authorized by a well-known CA be trusted by default on client browsers.  However, it is common for custom CAs to not be authorized by a well-known CA, and client browsers will warn about any certificates they issue.  Obviously users need to take care about trusting certificates from an unknown source.  In the worst case they would accept an unknown CA certificate when connecting to a financial website.