What is an SSL certificate?
An SSL certificate, the full name of which is Secure Sockets Layer Certificate, now commonly refers to its successor, the TLS certificate, is a type of digital certificate. Its primary function is to authenticate the identity of a website and establish an encrypted connection between the user’s browser and the website server. This encrypted connection ensures that all data transmitted between the two parties (such as passwords, credit card numbers, personal information, etc.) is securely encrypted, effectively preventing data from being stolen or tampered with during transmission. When a website has a valid SSL certificate installed, the browser’s address bar will display the “https://” prefix along with a security lock icon.
This certificate follows the “Public Key Infrastructure” (PKI) model. It contains the website’s public key, identification information about the website, the digital signature of the certificate-issuing authority, and other relevant details. When a user visits a website that uses HTTPS, the browser automatically requests the website’s SSL certificate from the server and initiates a complex verification process called the “SSL/TLS handshake” to confirm the validity of the certificate and the authenticity of the website.
The Core Types and Selection of SSL Certificates
Understanding the different types of SSL certificates is the first step in making the right choice. Based on the level of verification and the scope of coverage, they are mainly classified into the following categories:
Recommended Reading Detailed Explanation of SSL Certificates and Purchasing Guide: From Beginner to Expert, Ensuring Website Security。
Domain Validation Certificate
Domain name validation certificates are the type of certificate with the lowest level of verification and the fastest issuance process. The certificate issuing authority only verifies the applicant’s ownership of the domain name, typically by sending a verification email to the email address registered with that domain name or by setting up DNS resolution records. These certificates do not verify the actual legitimacy of the company or organization.
Such certificates are very suitable for personal websites, blogs, or testing environments. They provide basic encryption capabilities, but the company name will not be displayed in the browser address bar. Their cost is usually the lowest.
Organizational validation type certificate
Organizational validation certificates build upon DV (Domain Validation) certificates by adding an additional layer of verification to confirm the authenticity and legitimacy of the applying organization (such as a company or government agency). The Certificate Authority (CA) manually checks the applicant’s registration information in government or official databases, including the company name, address, phone number, and other relevant details.
The OV certificate embeds the verified information about these organizations into the certificate itself. Users can view this information by clicking on the lock icon in the browser address bar. This significantly enhances the credibility of the website, making it an ideal choice for commercial websites and corporate official portals.
Extended Validation Certificate
Extended Validation (EV) certificates represent the most stringent type of certificate with the highest level of trust. In addition to completing all the review steps required for regular OV certificates, the Certificate Authority (CA) also conducts additional, in-depth manual inspections to ensure that the entity applying for the certificate complies with legal and operational requirements.
Recommended Reading SSL Certificate Overview: From Beginner to Deployment – Locking the Security of Your Website。
On websites that have installed EV (Extended Validation) certificates, the browser address bar turns a prominent green color, and the name of the verified company is displayed directly. This provides the highest level of identity assurance for websites in industries with extremely high trust requirements, such as finance, e-commerce, and large enterprises.
Wildcard certificates and multi-domain certificates
Wildcard certificates use an asterisk (*) as a wildcard to protect a main domain name and all its subdomains at the same level. For example, a wildcard certificate issued for… *.example.com The certificate can provide protection for multiple aspects simultaneously. www.example.com、mail.example.com、shop.example.com It greatly simplifies the complexity of managing a large number of subdomains.
Multi-domain certificates allow the protection of multiple completely different domain names within a single certificate. For example, a SAN (Subject Alternative Name) certificate can protect multiple domain names at the same time. example.com、example.net and anothersite.orgIt is suitable for companies that have multiple independent brands or business lines.
How to purchase and deploy an SSL certificate
From selecting an SSL certificate to successfully enabling it, a series of clear steps must be followed.
Step 1: Generate a certificate signing request
Before purchasing a certificate, you need to generate a “Certificate Signing Request” (CSR) on your website server. This is an encrypted text file that contains your public key and information about your website. The process of generating a CSR creates a pair of keys: a private key and a public key. The private key must be securely stored on your server and must not be disclosed under any circumstances; the CSR, which contains the public key, needs to be submitted to the Certificate Authority (CA).
When generating a CSR (Certificate Signing Request), you need to provide accurate information such as your domain name, organization name (if applicable), and location. This information will be encoded into the final certificate.
Recommended Reading Comprehensive Analysis of SSL Certificates: Type Differences, Application Process, and Server Installation and Configuration Guide。
Step 2: Select and purchase the certificate
Choose the appropriate type of certificate based on the type and requirements of your website. You can purchase the certificate directly from globally renowned certificate authorities, or you can buy it through their authorized resellers, which may offer more competitive prices.
After submitting your purchase request, paste the content of the CSR (Certificate Signing Request) file you generated into the location specified by the CA (Certificate Authority), and complete the corresponding verification process based on the type of certificate you have chosen. For DV (Domain Validation) certificates, the verification usually takes a few minutes; for OV (Organizational Validation) or EV (Extended Validation) certificates, it may require several days for manual review.
Step 3: Install and configure the certificate
After the verification is completed, the CA (Certificate Authority) will send you the SSL certificate file that has been issued. Typically, you will receive a… .crt Or .pem Certificate files are in a specific format, and sometimes they also include intermediate certificate chain files.
You need to log in to your website server and bind the certificate file, the intermediate certificate chain file, and the previously generated private key file together. The specific steps vary depending on the type of server. For Nginx, you need to modify the configuration file to specify the paths for the certificate and private key; for Apache, you usually need to perform similar configuration settings. SSLCertificateFile and SSLCertificateKeyFile Instructions: After the configuration is complete, restart the web server to apply the new certificate.
Step 4: Force HTTPS redirection
After installing the certificate, your website can be accessed via HTTPS. However, to ensure that all traffic is encrypted and to prevent content duplication, you must configure your server to automatically redirect all HTTP requests to the corresponding HTTPS addresses.
In Nginx, this can be achieved by adding a server This is achieved by blocking port 80 and returning a 301 redirect. In Apache, this can be done by configuring the server settings accordingly. .htaccess The rewriting rules should be implemented within the files. Additionally, you should update the addresses of all internal links, images, scripts, and other resources on the website to ensure that they are using the HTTPS protocol.
Validation and Maintenance of SSL Certificates
Deployment is not the end; continuous validation and regular maintenance are equally crucial.
Verify whether the deployment was successful.
After the certificate is installed, you can use online SSL inspection tools for a comprehensive diagnosis. These tools will verify whether the certificate has been installed correctly, whether it is valid and trusted, as well as the strength of the encryption suite and the supported protocol versions. They will also identify any potential configuration issues, such as the use of insecure protocols or outdated encryption algorithms.
Visit your website in a browser and ensure that a lock icon is displayed in the address bar. Click on the lock icon to view detailed information about the certificate, including the recipient, the issuer, and the validity period. Make sure that all subpages and resources are loaded via HTTPS, and there are no warnings about “mixed content”.
Certificate Renewal and Update
SSL certificates have a fixed validity period, and the current industry standard is a maximum of 13 months. Certificate expiration is one of the most common causes of SSL errors on websites; browsers will prevent users from accessing expired websites.
You must renew your certificate before it expires. Typically, the certificate issuing authority will notify you via email before the expiration date. The renewal process is similar to the initial application; you can choose to generate a new CSR (Certificate Signing Request) or use the existing one. It is recommended to set up automatic renewal alerts or use a certificate management service that supports automatic renewal to prevent service interruptions due to negligence.
Monitoring and Revocation
In certain situations, such as a private key being leaked or a change in website ownership, you may need to revoke a previously issued certificate. Once revoked, browsers will refuse to accept the certificate during verification. You must submit a revocation request through the CA’s control panel and may be required to provide relevant evidence as per the CA’s requirements.
At the same time, it is recommended to continuously monitor the SSL/TLS configuration of the website and stay informed about the latest developments in the security community. As cryptography evolves, some encryption algorithms may be found to have vulnerabilities and become insecure. It is necessary to promptly update the server configuration to disable these insecure protocols and algorithms.
summarize
SSL certificates are the cornerstone of building a secure and trustworthy internet. This article provides a comprehensive overview of the entire process, from understanding their principles, identifying different types of certificates, purchasing and deploying them, to conducting subsequent verification and maintenance. For any website owner, deploying an SSL certificate that has been properly verified and configured is no longer an optional feature; it has become a necessary measure to protect user data, build brand trust, and meet the requirements of search engine rankings. Choosing the right type of certificate for your business, following best security practices during deployment, and establishing an effective renewal reminder system are crucial for ensuring the long-term security and stability of your website.
FAQ Frequently Asked Questions
What are the differences in the way DV, OV, and EV certificates are displayed in browsers?
DV (Domain Validation) certificates only display the HTTPS symbol and a lock icon. When you click on the lock icon for an OV (Organization Validation) certificate, you can view the certificate details, which include verified information about the organization. EV (Extended Validation) certificates, on the other hand, prominently display the name of the verified company or organization in the browser address bar, often accompanied by a green address bar, providing the highest level of visual trust indication.
Does applying for an SSL certificate necessarily require payment?
不一定。存在如 Let‘s Encrypt 这样的公益证书颁发机构，提供自动化的、完全免费的 DV 证书，其安全性与付费的 DV 证书相同，非常适合个人站点、开发测试等场景。但对于需要组织验证或扩展验证的商业网站，通常仍需选择付费的 OV 或 EV 证书。
Can one SSL certificate be used on multiple servers?
Sure, but there are conditions. As long as the servers are hosting the same domain name (or any domain name within the list of domains covered by the certificate), you can deploy the same certificate and private key on multiple servers. It’s important to note that the private key must be copied and distributed in a secure manner to prevent any potential leaks.
Will deploying an SSL certificate affect the website's access speed?
The performance overhead of modern SSL/TLS protocols is very low. The TLS handshake process does introduce a slight delay, but once the encrypted connection is established, the speed of subsequent communications is barely different from that of an unencrypted connection. On the contrary, since HTTPS allows the use of modern protocols such as HTTP/2, it can significantly improve page loading speeds in most cases. Therefore, performance should not be a reason for not deploying SSL certificates.
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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