In today's internet environment, data security is a fundamental principle. SSL certificates are the core technology for achieving this goal; they establish an encrypted channel between the client (such as a browser) and the server, ensuring that all transmitted data is not intercepted or tampered with. When you visit a website that uses HTTPS, the lock icon that appears in the address bar is a clear indication that the SSL certificate is in use and is functioning properly.
It is not just an encryption tool; it also serves as a “digital identity card.” The certificate is issued by a trusted certification authority and contains the identity information of the website owner. As a result, it performs two important functions: it encrypts data transmissions and verifies the authenticity of the website, effectively protecting against man-in-the-middle attacks and phishing attempts.
The core working principle of SSL certificates
The working mechanism of the SSL/TLS protocol is based on a combination of asymmetric and symmetric encryption, and this process is completed quickly without any noticeable impact on the user, which is known as the “SSL handshake”.
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Asymmetric encryption is used to establish secure communication channels.
When a client accesses an HTTPS website, the server first sends its SSL certificate (which contains the public key) to the client. The client (such as a web browser) then verifies whether the certificate-issuing authority is trustworthy, whether the certificate has expired, and whether the domain name matches the one being accessed. If the verification is successful, the client generates a random “session key.”
Symmetric encryption is used to encrypt the actual data.
The client uses the server’s public key to encrypt the “session key” and then sends it back to the server. Only the server, which possesses the corresponding private key, can decrypt the session key. Subsequently, both parties use this shared session key for fast symmetric encryption and decryption of their communications. This combination ensures the security of the key exchange as well as the efficiency of encrypting large amounts of data.
The main types of SSL certificates and how to choose them
Understanding the different types of certificates is the first step in making the right choice. Certificates are mainly classified based on the scope of verification and their functions.
Domain Validation Certificate
DV (Domain Validation) certificates are the ones with the lowest level of validation and the fastest issuance process (usually within a few minutes). The Certificate Authority (CA) only verifies the applicant's ownership of the domain name, for example, by sending a verification email to the email address registered for that domain. They are perfect for personal websites, blogs, or testing environments, as they provide basic encryption capabilities but do not display the company name on the certificate.
Organizational validation type certificate
OV certificates require a rigorous verification process, during which the CA (Certificate Authority) verifies the genuine and legal existence of the applying company (for example, by checking its business license). The issuance time typically takes 1–3 working days. The company name is displayed in the certificate details, which helps to prove the authenticity of the entity behind the website. These certificates are commonly used for enterprise-level websites and e-commerce platforms.
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Extended Validation Certificate
EV certificates are the most rigorously verified and highest-security level of certificates. In addition to completing all the verification processes required for OV certificates, the CA (Certificate Authority) also conducts more in-depth background checks on the issuing entity. A significant feature of EV certificates is that, in some browsers, the website address bar will directly display the green name of the enterprise when an EV certificate is installed, which greatly enhances user trust. These certificates are ideal for use in scenarios that require a high level of trust, such as banks, financial institutions, and large e-commerce platforms.
Multiple domain and wildcard certificates
In addition to verification levels, there are also classifications based on the scope of coverage. Multi-domain certificates allow the use of a single certificate to protect multiple completely different domain names. Wildcard certificates, on the other hand, enable the use of a single certificate to protect a primary domain name and all its subdomains at the same level. For example…*.example.com It can protect blog.example.com、shop.example.com It’s very convenient to manage.
How to purchase and apply for an SSL certificate
The process of obtaining an SSL certificate has become highly standardized, allowing users to make a choice based on their specific needs and budget.
First, you need to determine the type of certificate that is suitable for your website (DV, OV, EV) and whether you need a wildcard domain. You can then purchase the certificate from a reputable certificate authority (CA) or one of its authorized resellers. Common CAs include DigiCert, Sectigo, GlobalSign, and others.
After making the purchase, you need to generate a Certificate Signing Request (CSR) on your server or on the purchase platform. The CSR contains your public key as well as your company information (for OV/EV certificates). When generating the CSR, a pair of private and public keys will be created; the private key must be securely stored on your server and must not be disclosed under any circumstances.
After submitting the CSR (Certificate Signing Request) to the CA (Certificate Authority), the CA will perform the necessary verification based on the type of certificate you have selected. Once the verification is successful, the CA will send you the issued certificate files. Typically, you will receive a primary certificate file and, possibly, an intermediate CA certificate file. Both of these files need to be correctly installed on your server.
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Deploying an SSL certificate on a web server
After the certificate is issued, it must be correctly installed on the server to take effect. The following are the brief installation steps for common servers.
Nginx Server Deployment
In Nginx, you need to edit the website configuration file. The main step is to specify the paths for the certificate file and the private key.ssl_certificate The command is directed at your certificate file (which is usually located in a specific directory). .crt Or .pem format).ssl_certificate_key The instruction refers to the private key file you have generated..key After the configuration is complete, use it. nginx -t Test the configuration syntax, and then reload the Nginx service to apply the changes.
Apache Server Deployment
For Apache servers, you need to enable the SSL module in the virtual host configuration file and configure the relevant directives.SSLCertificateFile Point to your site’s certificate file.SSLCertificateKeyFile Point to your private key file.SSLCertificateChainFile Point to the intermediate CA certificate file (to ensure the certificate chain is complete). After saving the configuration, restart the Apache service.
Key checks after deployment
After the installation is complete, be sure to use an online tool to verify that the certificates have been installed correctly, that the certificate chain is intact, and that the secure TLS protocol versions are supported (it is recommended to disable SSLv2 and SSLv3 and use TLS 1.2 or higher). Additionally, you should permanently redirect all HTTP traffic to HTTPS for your website. This can be achieved through server configuration to ensure that users always access your site via a secure connection.
summarize
SSL certificates have evolved from an optional technology to a necessity for website operations. They protect user data through encryption, establish trust through authentication, and are also a positive factor in search engine rankings. Choosing the right type of certificate, purchasing it from a trusted source, and deploying and maintaining it on the server according to the correct procedures are essential skills that every website administrator should master. By following the guidelines in this article, you can systematically implement HTTPS encryption for your website, creating a safer and more trustworthy access environment for your users.
FAQ Frequently Asked Questions
What are the differences in the display of DV, OV, and EV certificates in browsers?
DV certificates usually only display a lock icon in the browser address bar. When you click on the lock icon to view the certificate details, you can see the name of the company that issued the certificate. In the past, EV certificates would directly display the company’s name in green in the address bar; however, in recent years, major browsers have gradually stopped this special visual representation. As a result, the visual appearance of EV certificates in the address bar is now similar to that of OV certificates. Nevertheless, the strict authentication standards behind both types of certificates remain unchanged.
What is the difference between a free SSL certificate and a paid one?
免费证书（如Let‘s Encrypt颁发的）通常是DV证书，非常适合个人站点或测试用途，能提供相同的加密强度。主要区别在于：免费证书有效期较短（约90天），需要频繁续签；通常不提供商业保修；在技术支持和服务保障上较付费证书有限。付费证书则提供更长的有效期、针对OV/EV的严格身份验证、更高的保修金额以及专业的技术支持。
Can an SSL certificate be used for multiple domain names?
Sure, but it depends on the type of certificate. A regular single-domain certificate can only protect one specific domain name. A multi-domain certificate allows you to include multiple different domain names in the same certificate. A wildcard certificate, on the other hand, can protect a domain name and all its subdomains at the same level. You need to choose the right type when purchasing based on your actual needs.
Will the website speed slow down after deploying HTTPS?
During the initial SSL handshake phase, there is a slight delay due to the need to exchange keys and verify certificates. However, with the optimization of the TLS protocol and the use of technologies such as session reconnection, this impact has become negligible. On the contrary, enabling HTTPS also allows the use of HTTP/2, which offers significant performance improvements over HTTP/1.1, often compensating for the handshake delay and overall enhancing the website loading speed. Additionally, search engines consider HTTPS as a positive factor in ranking, which has a positive impact on SEO.
What will happen if the certificate expires?
After the certificate expires, browsers and clients will display a severe “unsafe” warning when accessing the website, indicating that the connection is not secure. This can significantly hinder user access, leading to user loss and a decline in trust. Therefore, it is essential to renew and replace the certificate before it expires. It is recommended to set up calendar reminders or use certificate services that support automatic renewal to manage the certificate lifecycle.
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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