In today's internet environment, data security is of paramount importance. When you see a small lock icon in the browser address bar and a website address that starts with “https”, it is the SSL certificate that plays a crucial role. The SSL certificate acts as a digital “passport” that establishes an encrypted channel between the server and the user’s browser, ensuring that the data being transmitted is not intercepted or tampered with, and it also verifies the authenticity of the website.
The core working principle of SSL certificates
The working principle of an SSL certificate is based on a combination of asymmetric and symmetric encryption. The process can be summarized into two stages: “handshake” and “communication,” with the aim of ensuring both security and efficiency.
When a user visits a website that uses HTTPS for the first time, the SSL/TLS handshake protocol is initiated. The browser first sends a “Client Hello” message to the server, which includes information about the encryption protocols it supports. In response, the server sends a “Server Hello” message along with its SSL certificate.
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Once the browser receives the certificate, it performs a series of critical verifications: it checks whether the certificate was issued by a trusted certificate authority, whether it is still within its validity period, and whether the domain name specified in the certificate matches the domain name being accessed. If all these verifications pass, the browser assumes that the server is legitimate and trusts its identity.
Subsequently, the encrypted communication officially begins. The browser uses the server’s public key contained in the certificate to generate a random “session key” and sends it to the server. Since only the server with the corresponding private key can decrypt this information, the security of the key exchange is ensured. Once both parties have obtained the same session key, they switch to using this key for symmetric encryption to transmit data during the session. Symmetric encryption is faster and more suitable for processing large amounts of data.
The main types of SSL certificates and their applicable scenarios
Based on the level of strictness and the scope of coverage of the validation, SSL certificates are mainly divided into three categories. Users should choose the appropriate certificate according to the nature and requirements of their website.
Domain Validation Certificate
DV (Domain Validation) certificates represent the most basic level of verification. The certificate issuing authority only verifies the applicant’s control over the domain name, for example, by sending a verification email to the email address registered for that domain name or by placing a specified verification file in the website’s root directory. The issuance process is extremely fast, usually taking only a few minutes.
The DV certificate only displays a padlock icon and the HTTPS protocol; it does not show the company name. It is suitable for personal blogs, small demonstration websites, or internal testing environments that require a quick implementation of HTTPS, primarily providing basic encryption capabilities.
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Organizational validation type certificate
OV (Organizational Validation) certificates provide a higher level of trust. In addition to verifying the ownership of the domain name, the CA (Certificate Authority) also conducts a manual review of the authenticity and legitimacy of the applying organization, for example, by checking the company’s official registration documents. As a result, the certificate details will include the verified name of the company.
OV certificates significantly enhance the credibility of a website, clearly demonstrating to visitors that the entity behind the website is a legally registered organization. They are widely used on corporate official websites, portal sites, as well as on e-commerce platforms that handle user login and data exchange.
Extended Validation Certificate
EV (Extended Validation) certificates provide the highest level of authentication and security. The verification process is the most stringent, and the CA (Certification Authority) conducts a comprehensive background check on the applying organization based on a set of standardized criteria.
The most prominent feature is that in browsers that support EV (Extended Validation) certificates, the address bar not only displays a lock icon but also highlights the verified company name in green. This provides the most intuitive and reliable indication of trust for websites that require a high level of security, such as those involved in online transactions, finance, or payment gateways.
In addition, depending on the domain name coverage requirements, there are single-domain-name certificates, multi-domain-name certificates, and wildcard certificates. Wildcard certificates can protect a primary domain name and all its subdomains at the same level, which makes them very efficient for businesses with multiple sub-sites to manage.
The complete process for obtaining and installing an SSL certificate
Obtaining and deploying SSL certificates is a standardized process that mainly includes several key steps: application, verification, installation, and configuration.
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The first step is to generate a Certificate Signing Request (CSR). This is typically done through your server management panel or in the command line. During the CSR generation process, a pair of keys is created: a private key and a CSR file that contains the public key as well as organizational information. The private key must be kept strictly confidential, while the CSR file is used to be submitted to the Certificate Authority (CA).
The second step is to select and submit your application. You can purchase the appropriate type of certificate from CA or its authorized resellers based on your needs. During the purchase process, make sure to submit the CSR (Certificate Signing Request) file that was generated in advance. For OV (Organizational Validation) and EV (Extended Validation) certificates, you will also need to upload or prepare the relevant organizational certification documents accordingly.
The third step is to complete the verification process. The CA (Certificate Authority) will perform the verification at the appropriate level based on the type of certificate you have applied for. DV (Domain Validation) certificates are verified the fastest; OV (Organization Validation) and EV (Extended Validation) certificates require more time for manual review. Once the verification is successful, the CA will send you the issued certificate file via email.
The fourth step is installation and deployment. You need to upload the received certificate file and the previously generated private key file to your server, and then configure them in your web server software. Whether it’s Apache, Nginx, or IIS, the essence of the configuration is to specify the paths for the certificate file and the private key file. Once the configuration is complete, restart the web service to apply the new certificate.
Maintenance and Security Enhancement After Deployment
After successfully installing the SSL certificate, it is necessary to carry out a series of follow-up maintenance and optimization tasks to ensure its continued validity and security.
The top priority is to implement a full-site HTTPS redirection. By configuring the servers, all HTTP requests should be automatically and permanently redirected to their corresponding HTTPS addresses. This will prevent users from accessing insecure pages due to entering old URLs or clicking on outdated links, and it will also help search engines prioritize the indexing of secure pages.
Secondly, it is essential to manage the lifecycle of certificates and renew them in a timely manner. SSL certificates have a clear expiration date. Make sure to renew and re-install the certificate before it expires; otherwise, an expired certificate will cause browsers to issue serious security warnings, disrupting the normal access to the website. It is recommended to set up calendar reminders or use certificate services that support automatic renewal.
Finally, strengthen the security configuration. Only enable the TLS 1.2 or later protocols and disable the older, insecure SSL versions. Select a strong encryption suite and enable HSTS (HTTP Strict Transport Security). HSTS instructs browsers to use HTTPS to connect to the website for a specified period of time, effectively protecting against SSL stripping attacks. You can use online SSL security testing tools to regularly scan your website’s configuration and identify and fix any potential security vulnerabilities.
summarize
SSL certificates are the cornerstone of secure and trustworthy online communications. They use sophisticated cryptographic mechanisms to establish an encrypted and authenticated channel between users and websites. Every step in the process—from understanding the principles of the handshake and encryption processes, to selecting the appropriate type of certificate (DV, OV, or EV) based on the business requirements, to completing the entire process from application, verification, to installation and maintenance—is essential. In today’s world, deploying and maintaining valid SSL certificates is not only a technical best practice but also a fundamental manifestation of responsibility towards all website visitors.
FAQ Frequently Asked Questions
Why do some HTTPS websites still display as “unsecure” in browsers?
This is usually not because the SSL certificate itself is invalid, but rather because the page contains mixed (secure and insecure) content. For example, the web page code may reference images, JavaScript files, or CSS files using the “http://” protocol in plain text. The browser then assumes that the entire page is insecure and displays a “not secure” warning. This issue can be resolved by ensuring that all resources are loaded via HTTPS.
Are free SSL certificates sufficient to meet the needs of commercial websites?
对于许多中小型商业网站而言，由Let‘s Encrypt等机构提供的免费DV证书在加密强度上与付费DV证书无异，完全可以满足基础的安全需求。然而，如果网站需要展示已验证的企业身份以建立更强的客户信任（如电商、金融），那么显示公司名称的OV或EV付费证书则是更专业的选择。付费证书通常还附带技术支持和保障。
How long is the validity period of an SSL/TLS certificate, and why is it constantly being shortened?
Currently, the maximum validity period for SSL certificates issued by major certificate authorities is 398 days. The shortening of the validity period is a trend in the industry towards enhanced security. This measure encourages websites to update their key and certificate information more frequently, thereby reducing the risks associated with the long-term exposure of private keys. It also ensures that outdated or unmanaged website certificates become invalid more quickly.
Will the website loading speed slow down after installing the SSL certificate?
During the SSL/TLS handshake process at the beginning of a connection establishment, there is indeed a slight increase in latency due to the encryption calculations, typically measured in milliseconds. However, modern server hardware and optimized protocols have greatly reduced this impact. More importantly, the modern HTTP/2 protocol requires the use of HTTPS, and features such as HTTP/2 multiplexing and header compression can significantly improve page loading performance. Therefore, overall, the net effect of enabling HTTPS on both speed and user experience is positive.
What's next, what's next?
Extended reading and practical knowledge
The following are related to the topic of this article and are suitable for further in-depth reading. Prioritize starting with the article that is closest to your current problem, and gradually expanding to surrounding topics usually works better.
- What is an SSL certificate? A comprehensive explanation from its principles to the process of applying for and using it.
- What is an SSL certificate? A comprehensive guide to understanding the principles, types, and installation procedures of digital certificates.
- In-depth Analysis of SSL Certificates: From Beginner to Expert – Comprehensive Protection for Website Security
- What is an SSL certificate and how does it work
- Comprehensive Guide to SSL Certificates: From Principles and Types to Practical Details on Deployment and Management
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