What is an SSL certificate? A comprehensive guide from type to installation

In today's internet environment, data security is of utmost importance. When you see a lock icon in the browser address bar or when a website address starts with “https”, it means that the website is using an SSL certificate. An SSL certificate is a digital security mechanism that establishes an encrypted communication channel between the user’s browser and the website’s server.

This encryption process prevents sensitive data (such as login credentials, credit card information, and personal privacy) from being stolen or tampered with by third parties during transmission. It’s like creating a secure, encrypted tunnel for the data to travel across public networks. In addition to encryption, SSL certificates also provide authentication, ensuring that visitors are communicating with a legitimate, verified server, rather than a phishing website.

The core working principle of SSL certificates

The SSL/TLS protocol operates by combining asymmetric encryption with symmetric encryption. This process is automatically initiated the moment a user accesses a website and is commonly referred to as the “SSL handshake.”

Recommended Reading A Comprehensive Guide to SSL Certificates: From Principles and Types to the Entire Process of Application and Deployment。

Asymmetric encryption is used to establish secure communication channels.

When a user attempts to connect to an HTTPS website for the first time, the server sends its SSL certificate (which contains the public key) to the user’s browser. The browser then uses the public key from the certificate to encrypt a randomly generated “session key.” Only the server, which possesses the corresponding private key, is able to decrypt this encrypted session key. This process ensures the security of the key exchange.

Bluehost SSL Certificate

BlueHost SSL Certificates offer 1-2 year extension options, support for RSA or ECC algorithms, key lengths up to 4096 bits, and up to $1.75 million in protection.

From $7.49 USD per month

Access to Bluehost SSL Certificates →

hosting.com SSL Certificate

Affordable DV, OV, EV SSL certificates, up to 256-bit encryption, 5 ~ 1 million USD protection amount, 24/7 support

From $2.5 USD per month

Visit hosting.com SSL Certificates →

Symmetric encryption enables efficient communication.

Once the server decrypts the “session key” using its own private key, both parties use this same key to encrypt and decrypt all subsequent communication data. Symmetric encryption is much faster than asymmetric encryption and is suitable for encrypting large amounts of data that are actually transmitted. The entire handshake process is completed in milliseconds, establishing a secure and efficient connection for the users.

Detailed explanation of the main types of SSL certificates

Based on different verification levels and use cases, SSL certificates are mainly divided into three categories to meet the needs of various users.

Domain Validation Certificate

DV (Domain Validation) certificates are the type of certificate with the lowest level of verification and the fastest issuance process. The certificate authority only verifies the applicant's ownership of the domain name (usually through email or DNS records). They provide basic encryption capabilities but do not verify the true identity of the company or organization. As a result, only a lock icon is displayed in the browser address bar. DV certificates are suitable for personal websites, blogs, or testing environments.

Organizational validation type certificate

OV (Organic Trust) certificates provide a higher level of trust. In addition to verifying the ownership of the domain name, the CA (Certificate Authority) also checks the authenticity of the applying organization, for example by verifying its registration information with government authorities. The certificate details will include the verified name of the company. This reassures users that they are interacting with a legitimate entity, and such certificates are commonly used for corporate websites and commercial platforms.

Recommended Reading SSL Certificate Guide: From Beginner to Expert – Ensuring Website Security and Trustworthiness。

Extended Validation Certificate

EV certificates are the most rigorously verified and highest-trusted type of certificate. Applicants must undergo the most comprehensive identity checks. The most distinctive feature of EV certificates is that, in browsers that support them, the address bar not only displays a lock icon but also the company’s name in green. This significantly enhances users’ trust in the website, making them the preferred choice for financial institutions, e-commerce platforms, and other websites with high security requirements.

How to install an SSL certificate for a website

Installing an SSL certificate involves a series of steps from purchasing the certificate, verifying its authenticity, to configuring it on the server. Although the specific procedures vary depending on the server environment, the general process is as follows:

Step 1: Generate a certificate signing request

First of all, you need to generate a CSR (Certificate Signing Request) file on the website’s server. This process will create a pair of keys: a private key (which must be securely stored on the server and never disclosed) and a CSR file that contains information about the server and your company. The CSR file will then be submitted to the certificate authority.

UltaHost SSL Certificate

DV, EV, OV certificates, up to $1,750,000 USD coverage, unlimited sub-domains, iOS and Android apps, discounted 20% per month, $15.95 USD onwards, 30-day money-back guarantee

Visit UltaHost

Step 2: Submit for verification and obtain the certificate

Submit the CSR (Certificate Signing Request) file to the CA (Certificate Authority) of your choice. Depending on the type of certificate you purchased (DV, OV, or EV), the CA will perform a verification process of the corresponding level. Once the verification is successful, the CA will issue your SSL certificate file (which is usually a string of encrypted text) and may also include an intermediate certificate chain.

Step 3: Install the certificate on the server

Upload the certificate file (as well as the certificate chain file) issued by the CA to your server. You will need to configure your web server software (such as Apache, Nginx, or IIS) to correctly associate the certificate file, the private key file, and any certificate chain files with the appropriate locations, and to enable the SSL/TLS protocol. Finally, restart the server to apply the configuration changes.

Step 4: Testing and Enforcing HTTPS

After the installation is complete, be sure to use an online tool to verify that the certificate has been installed correctly, is valid, and contains no errors. Next, you should configure your website to redirect all HTTP requests to HTTPS, ensuring that users always access the site via a secure connection.

Recommended Reading What is an SSL certificate? A comprehensive guide from beginner to expert – understanding the foundation of HTTPS security.。

summarize

SSL certificates have evolved from an optional technology to a fundamental component for the secure operation of websites. They protect data privacy through encryption, establish user trust through authentication, and are also essential for search engine rankings as well as for the functionality of modern browsers. Understanding the differences between various types of certificates, such as DV, OV, and EV, can help you make the right choice based on the nature of your website. Whether you are a individual webmaster or a corporate IT professional, mastering the process of applying for and installing SSL certificates is a crucial step in creating a secure and trustworthy online environment.

FAQ Frequently Asked Questions

Are HTTPS and SSL the same thing?

The two are closely related, but not completely identical. SSL (and its successor, TLS) are the underlying security protocols used for encryption. HTTPS, on the other hand, is a secure hypertext transfer protocol that builds upon the HTTP protocol by incorporating SSL/TLS. In simple terms, HTTPS = HTTP + SSL/TLS.

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

免费证书（如Let's Encrypt颁发）通常是DV证书，提供与付费DV证书相同强度的加密。主要区别在于技术支持、保修承诺和证书功能。付费证书提供更专业的客户支持、更高的赔付保障，并且提供OV或EV等需要人工验证的类型，这些是免费证书不具备的。

Will the installation of an SSL certificate affect the website's speed?

Enabling SSL for encryption and decryption does indeed consume a small amount of computing resources on both the server and the client side. However, modern hardware, along with optimized TLS protocols (such as TLS 1.3), have reduced this impact to almost negligible levels. On the contrary, the overall experience may be improved due to factors such as the higher caching efficiency of HTTPS sites. Considering the security benefits and SEO advantages, this minor performance trade-off is well worth it.

How should I choose between a multi-domain certificate and a wildcard certificate?

It depends on the structure of your domain names. If you need to protect multiple completely unrelated main domain names (for example... example.com and anotherexample.netIn such cases, you should choose a multi-domain certificate. If you need to protect a primary domain name and all its subdomains at the same level (for example... *.example.comCan provide protection. blog.example.com， shop.example.comIn such cases, choosing a wildcard certificate is more cost-effective and efficient.