Comprehensive Analysis of SSL Certificates: From Principles to Installation, Solve Your Website's Security and Trust Issues in 10 Minutes

The core principle of SSL certificates

The core principle of an SSL certificate is based on asymmetric encryption technology, also known as public-key encryption. This mechanism involves a pair of keys: a public key and a private key. The public key is made available to the public and is used to encrypt data, while the private key is kept secret by the server and is used to decrypt the data. When a visitor (client) attempts to connect to your website, the server will first present its SSL certificate.

The certificate contains the server’s public key and is digitally signed by a trusted third party, namely the certificate authority (CA), to verify its authenticity. Clients (such as web browsers) have built-in root certificates for all trusted CAs and use these root certificates to verify the validity of the server’s certificate. Once the verification is successful, a temporary “session key” is generated through negotiation between the client and the server. This session key is used for symmetric encryption in subsequent communications, ensuring both strong encryption and avoiding the high performance overhead associated with asymmetric encryption.

Fundamentally, SSL certificates address two key issues: the encryption of data transmission and the authenticity of a website’s identity. Encryption ensures that information cannot be eavesdropped on or tampered with, while authentication confirms to visitors that the website they are accessing is indeed the one it claims to be, and not a phishing site.

Recommended Reading Deeply Understanding SSL Certificates: A Comprehensive Guide to Their Working Principles, Type Selection, and Deployment。

The main types of SSL certificates

Based on different verification levels and security requirements, SSL certificates are mainly divided into the following types, each with varying levels of trust, prices, and issuance speeds.

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Domain Validation SSL Certificate

This is the most basic type of SSL certificate. The Certificate Authority (CA) only verifies the applicant’s control over the domain name, for example, by sending a verification email to the WHOIS email address or requiring the setting of specific DNS records. The issuance process is very fast and is usually completed within a few minutes.
DV certificates are inexpensive or even free, making them suitable for personal websites, blogs, or testing environments. They offer basic encryption capabilities, but they only display a security lock icon in the browser address bar without showing the company name, which limits their effectiveness in building user trust.

Organizational Validation SSL Certificate (OV SSL)

OV (Organizational Validation) certificates provide a higher level of authentication. In addition to verifying the ownership of the domain name, the CA (Certificate Authority) also manually verifies the actual existence of the applying organization, including checking its information in government or commercial registration agencies. The verification process typically takes 1–3 working days.
After issuance, the name of the applying company can be found in the detailed information of the certificate. This type of certificate is suitable for commercial websites, corporate portals, and other scenarios where it is necessary to demonstrate an official identity, as it conveys a stronger signal of credibility to users.

Extended Validation SSL Certificates (EV SSL)

EV certificates provide the highest level of verification and trust. The approval process is the most stringent; the CA (Certificate Authority) conducts in-depth background checks to ensure that the organization is a legitimate and legally operating entity. The issuance process can take several days.
Websites that install EV (Extended Validation) certificates display a security lock in the address bar of mainstream browsers, as well as the company’s name in green. This feature was once standard for high-risk websites in the banking, finance, and e-commerce sectors, as it helped to maximize users’ trust. Although the prominence of the green address bar has diminished with changes in browser display methods, the strict verification standards associated with EV certificates remain the highest standard for ensuring the authenticity of a website’s identity.

In addition, there are single-domain certificates, multi-domain certificates, and wildcard certificates, which are classified based on the scope of domain name coverage. Wildcard certificates can protect a primary domain name and all its subdomains at the same level, providing convenience and cost-effectiveness for enterprises with complex subdomain structures.

Recommended Reading Understanding SSL Certificates: A Complete Guide from Principles to Deployment。

How to Choose and Buy SSL Certificates

When faced with a wide variety of certificate types and providers, making a wise choice requires considering the following key factors:

The first step is to determine the verification level. This should be decided based on the nature of the website: Personal blogs or test sites can opt for DV (Domain Validation) certificates; corporate websites that serve as a public face for a company are suitable for OV (Organization Validation) certificates; whereas websites that handle online transactions, financial data, or sensitive information should prioritize EV (Extended Validation) certificates to establish the highest level of trust.

The next consideration is the need for domain name coverage. If there is only one main domain name, a single-domain certificate will suffice. However, if it is necessary to protect multiple completely different domain names (for example… example.com and example.netIn that case, you should choose a multi-domain certificate. If you have a large number of subdomains (for example,... shop.example.com， blog.example.comThen, a wildcard certificate…*.example.com) is the most cost-effective and efficient option.

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When selecting a certificate provider, it is important to consider compatibility, reputation, and the quality of services provided. Make sure to choose a top-tier CA (Certificate Authority) that is globally trusted, so that its root certificates are built into all operating systems and browsers, to avoid any warnings for users. Additionally, compare the prices of different CAs, the amount of warranty coverage (i.e., the compensation offered in case of losses due to certificate expiration), and the quality of customer support. Free certificate issuing organizations are an excellent and trustworthy option, especially for DV (Domain Validation) certificates.

Detailed Installation and Deployment Guide

The process of deploying an SSL certificate can be summarized as follows: generating an application file, submitting it for verification, obtaining the certificate, and then installing and configuring it. The following example illustrates the common installation process on a cloud server.

Step 1: Generate a CSR (Certificate Signing Request) and a private key.

The first step is to generate a Certificate Signing Request (CSR) and the corresponding private key on your server. The private key is the core of security; it must be kept absolutely confidential and properly backed up. Taking a Linux server using OpenSSL commands as an example, you can generate both the CSR file (which contains your domain name, company information, and the public key) and the private key file with a single command.

Recommended Reading What is an SSL certificate: a comprehensive guide to its principles, types, and installation and configuration。

Step 2: Submit the verification and obtain the certificate.

Submit the content of the generated CSR (Certificate Signing Request) file to the certificate authority (CA) of your choice. The CA will perform the appropriate validation based on the type of certificate you are applying for (DV, OV, or EV). Once the validation is successful, the CA will issue the SSL certificate file, which typically includes a certificate chain..crtOr.pemThe files will be provided to you via email or the console. Additionally, you may need to download the intermediate certificate files from the CA (Certificate Authority).

Step 3: Server Installation and Configuration

Upload the obtained certificate file, intermediate certificate file, and the private key file you generated to the designated directory on the server. The specific configuration methods vary depending on the server software you are using.
- 对于Nginx：需要在服务器块配置文件中修改 ssl_certificate(Specify the certificate file and the intermediate certificate) and ssl_certificate_keySpecify the private key file and listen on port 443.
- 对于Apache：需要在虚拟主机配置中使用 SSLCertificateFile、SSLCertificateKeyFile and SSLCACertificateFile Instructions for specifying the site certificate, private key, and certificate chain file separately.

After the configuration is completed, restart the web server to apply the new settings. Next, use an online SSL validation tool to check whether the certificate has been installed correctly and whether the certificate chain is intact. Additionally, configure a forced redirect from HTTP to HTTPS to ensure that all traffic is transmitted over an encrypted connection.

summarize

SSL certificates have evolved from an optional security enhancement to an essential infrastructure component for modern website operations. They lay the foundation for online security through two core functions: encryption and authentication. Understanding the differences between various types of certificates, such as DV, OV, and EV, allows us to make the right choice based on the website’s specific business needs and required level of trust. The deployment process, from generating the CSR (Certificate Signing Request) to configuring the server, involves technical details, but with the advancement of tools and services, the barriers to implementing HTTPS have significantly decreased. Setting up HTTPS is not only necessary to protect user data and avoid security warnings from browsers; it is also a crucial step in establishing a professional and trustworthy brand image. Every website owner should consider this a core task that must be completed before launching their website.

FAQ Frequently Asked Questions

What is the relationship between SSL certificates and HTTPS?

SSL (and its subsequent version, TLS) is a protocol used to enable encrypted communication. An SSL certificate serves as the necessary digital “identity card” and “key” to activate the use of this protocol.

When a website has a valid SSL certificate installed and the server is properly configured, an encrypted SSL/TLS connection can be established between the server and the client. In this case, the protocol used by the browser to access the website is HTTPS, which stands for “HTTP over SSL/TLS.” It can be said that the SSL certificate is the cornerstone of implementing HTTPS.

What is the difference between a free SSL certificate and a paid one?

主要区别在于验证级别、保障服务和支持范围。免费证书（如Let‘s Encrypt颁发的）通常是DV证书，提供基础的加密功能，签发自动化且快。但其有效期较短（通常90天），需要定期自动续期，且一般不提供技术支持和资金担保。

Paid certificates offer higher levels of validation, such as OV (Organizational Validation) and EV (Extended Validation), which can display organizational information and thereby build greater trust with users. They have a longer validity period (1–2 years) and come with round-the-clock technical support, as well as liability warranties worth hundreds of thousands or even millions of dollars. For commercial websites, the brand trust and security benefits provided by paid certificates are irreplaceable by free certificates.

Will deploying an SSL certificate affect the speed of a website?

Enabling HTTPS encryption does indeed introduce a slight increase in performance overhead, mainly during the “handshake” phase of establishing a secure connection. This process requires additional computational resources for key exchange and authentication.

However, with the improvement of hardware performance and the optimization of new protocols such as TLS 1.3, the impact of these issues has become negligible, and users are generally unable to notice any difference. On the contrary, enabling HTTPS allows the use of modern web protocols like HTTP/2, which support multiplexing and reduce the number of connections, potentially significantly improving website loading speeds. Overall, the benefits of security far outweigh the minor performance sacrifices.

What should I do if my website displays “Unsecure” after installing the SSL certificate?

This situation usually indicates that there is an issue with the installation or configuration of the SSL certificate. First, check whether the certificate has been installed correctly and is not expired, and make sure that the URL being accessed is valid. https:// Beginning.

Secondly, the most common reason is “incomplete certificate chain.” You need to ensure that not only the site certificate for your domain name is installed in the server configuration, but also the intermediate certificates provided by the CA (Certificate Authority) are correctly installed. This is necessary to build a complete trust chain that allows browsers to trace back to the built-in root of trust.

In addition, it is also necessary to check whether HTTP resources (such as images and scripts) are being loaded from the web page using the HTTP protocol. Modern browsers will also mark such situations as “unsafe,” and it is required to change all references to these resources to HTTPS links or use relative protocol links.