A certificate server is a type of computer server that checks incoming public keys and validates them to ensure the user or users are real. Digital public keys are similar to physical keys used on doors, except they are made of encrypted data. One of the major functions of a certificate server is to validate these keys, or ensure the keys are real, and make sure the person or people attached to the keys are not hackers or malicious users. While most certificate servers are closed source, meaning people have to pay to use them, there are a number of free, open source solutions available for websites. These servers are used mostly on membership-based websites and secure websites such as government and medical websites.
A public key is a digital string of information given to each website member. Much like a physical key that has unique teeth to make it suitable for only one lock, a public key is made of encrypted data and is only given to one user. Such a key protects the user, because he or she is able to securely access the website; it also ensures the security of the website, because the public is restricted from entering the website without providing the correct key.
The validation process of a certificate server is complex, with many algorithms involved, yet it is simple to understand. When someone tries to gain access to a website, the certificate server checks his or her public key. The server goes through its records to ensure the key is real and the member attached to the key is in good standing. While this cannot keep out hackers if they have one of the public keys, it otherwise works very well at restricting their access.
Most certificate servers are closed source, but there are a number of open source servers that website owners can use for security. In terms of functionality, both closed and open source tend to be nearly identical. Open source servers' open code presents a unique advantage, however, because software engineers and programmers can manipulate the open code to create new tools.
The two most common users of a certificate server are membership-based websites and high-security websites. Membership-based websites include forums, news groups and any website that requires the user to sign up; these websites may or may not charge for access. High-security websites typically include medical and government websites. Most of these websites have a public section, but secure areas can only be accessed by passing through certificate servers.