An SSL certificate is a digital certificate used to establish an encrypted connection between a website and its visitors. It does two things: first, it encrypts data in transit; second, it verifies the website's identity. The former prevents information from being stolen or tampered with during transmission, while the latter lets visitors confirm that the site they have opened is indeed the intended one.
What problem it solves
- Data encryption: Sensitive data such as login credentials, form contents, and payment information exists in ciphertext form during transmission.
- Identity verification: Certificates are issued by trusted authorities, which reduces the risk of phishing sites impersonating a legitimate site.
- Trust indicator: Once enabled, the browser address bar displays a padlock icon and the HTTPS prefix.
- Search preference: Major search engines favor websites that have HTTPS enabled.
Common classification methods
By validation level, certificates are usually divided into three types: those that verify only domain ownership, which are issued quickly and suit personal sites or test environments; those that also verify company information, which suit corporate websites; and those with the strictest validation, which display the organization name in some browsers and are mostly used in scenarios with high trust requirements, such as finance and e-commerce.
By coverage scope, they are divided into certificates that protect a single domain, those that protect multiple different domains, and wildcard certificates that protect a primary domain and all of its subdomains.
How it works
When a visitor first accesses the site, the browser and server first complete a handshake: the server presents its certificate, and the browser checks whether the certificate is valid, whether it was issued by a trusted authority, and whether it is within its validity period. Once verification passes, the two parties negotiate an encryption method, and all subsequent data is transmitted in ciphertext.
Deployment essentials
The standard process is: generate a certificate signing request on the server, submit it to the issuing authority and complete validation, install the certificate file once received, and configure the website to enforce HTTPS.
One point that is easily overlooked: certificates have a validity period, and failing to renew before expiry will make the website directly inaccessible, so it is recommended to enable automatic renewal. In addition, if the page still references unencrypted external resources, a mixed content warning will appear, and this needs to be handled as well.
For most enterprises, there is no need to delve into the details of encryption algorithms; just confirm three things: the certificate is within its validity period, the configuration is correct, and HTTPS is enforced site-wide. If these three conditions are met, the task can be considered up to standard.