This article will guide you through understanding the differences between SSL certificates and TLS.

　　In modern website operations, secure communication has become an indispensable part. Whether it's an e-commerce website, a blog, or a corporate website, it's essential to ensure that user data is not stolen or tampered with during transmission. In this process, many novice website owners encounter two frequently confused concepts: SSL certificates and TLS. They seem to refer to the same thing, but they are fundamentally different. Understanding their relationship is crucial for website security, SEO optimization, and future maintenance.

　　First, let's understand SSL certificates. SSL was originally used to implement encryption in internet communication. An SSL certificate is actually a digital certificate issued by an authoritative organization, and its main functions are:

　　1. Authentication: Proving to visitors that your site is genuine and trustworthy, and not a phishing or impersonating website.

　　2. Encrypted Communication: Ensuring that data transmitted between the client (browser) and the server is encrypted, preventing man-in-the-middle attacks.

　　3. Data Integrity: Preventing data from being tampered with during transmission.

　　When we see https:// and a green padlock icon in the browser's address bar, this is due to an SSL certificate. It can be Domain Validation (DV), Enterprise Validation (OV), or Extended Validation (EV), with different validation levels indicating different levels of trust.

　　Next, let's look at TLS. TLS is an upgraded version of SSL and is the mainstream security protocol used on the internet today. Although the names are different, it continues the basic design philosophy of SSL while fixing security vulnerabilities present in early SSL and introducing more secure encryption algorithms.

　　In short:

　　SSL is a historical concept, an early protocol;

　　TLS is a modern standard, and currently, almost all encryption protocols used by browsers and servers are TLS.

　　This leads many people to mistakenly believe that SSL and TLS are two different technologies, but a more accurate statement is: an SSL certificate is the certificate itself, and TLS is the security protocol that runs on the certificate. SSL certificates are now typically used under the TLS protocol.

　　Having understood the relationship between the two, let's look at how they work.

　　1. Handshake Phase: The client initiates a connection request, and the server returns a certificate. The client verifies the certificate's validity (whether it was issued by a trusted CA, whether it has expired, and whether the domain name matches). 2. Key Negotiation: The client and server negotiate a symmetric encryption key for subsequent communication. The TLS protocol uses a more secure algorithm (such as ECDHE) to generate the session key during the handshake phase.

　　3. Encrypted Communication: After the handshake, data between the client and server is transmitted using symmetric encryption. Early versions of SSL were relatively weaker in encryption strength and algorithms, while TLS provides stronger and more secure encryption options.

　　4. Data Integrity Check: Each transmitted data includes verification information to prevent tampering.

　　It can be seen that SSL certificates are merely a medium for identity and key verification, while the TLS protocol is the set of rules that actually performs encryption, decryption, and integrity verification.

　　For novice website owners, understanding the differences between the two is crucial in three aspects:

　　1. Browser Compatibility: Modern browsers no longer support SSL 2.0/3.0; using TLS ensures compatibility and security.

　　2. SEO and Access Security: Search engines tend to prioritize indexing HTTPS websites, and the security of HTTPS relies on the strength of the TLS protocol, not just the certificate itself.

　　3. Certificate Selection and Deployment: When purchasing or applying for an SSL certificate, don't worry too much about "SSL or TLS," as the certificate itself can be used under the TLS protocol. The key is to ensure that the server is correctly configured with the TLS protocol and encryption algorithm.

　　In practice, the deployment of SSL certificates and TLS also differs:

　　SSL Certificate Application and Installation: Users apply for a certificate from a CA, verify the domain name or company identity, download the certificate, and install it on the server. After installation, the certificate is used for authentication during the handshake phase.

　　TLS Configuration: Enable the TLS protocol (such as TLS 1.2 or TLS 1.3) on the server and configure the encryption algorithm and protocol version. Most modern web servers (such as Nginx, Apache, IIS) support multiple versions of TLS, ensuring compatibility with both older and newer clients.

　　Besides these basic differences, SSL and TLS also differ in terms of security. Early versions of SSL (especially SSL 2.0 and 3.0) had several known vulnerabilities, such as the POODLE attack. The TLS protocol addresses these issues with a more rigorous handshake process and stronger encryption algorithms, while also supporting forward secrecy, ensuring the security of past communications even if the server's private key is compromised.

　　FAQs:

　　Q: Are SSL and TLS two different certificates?

　　A: No. An SSL certificate is the certificate itself; TLS is the security protocol that runs the certificate.

　　Q: Can I still use the SSL certificate I bought?

　　A: Yes. Modern servers use SSL certificates under the TLS protocol.

　　Q: Why does my browser display a "Not Secure" message?

　　A: This could be due to an expired certificate, an untrusted CA, or improper TLS configuration on the server.

　　Q: What is the difference between TLS 1.3 and TLS 1.2?

　　A: TLS 1.3 offers a faster handshake, more secure encryption algorithms, reduced latency, and is better suited for high-concurrency scenarios. Q: What are the most common SSL/TLS configuration issues that novice website owners overlook?

　　A: Enabling expired or insecure protocol versions, weak encryption suites, or certificate-domain mismatches.

　　In summary, SSL certificates handle authentication, while the TLS protocol handles data encryption. Understanding the differences and connections between the two not only helps novice website owners correctly deploy HTTPS but also avoids common SEO, compatibility, and security issues. As long as the certificate is valid and the protocol is configured correctly, website communication can be secure and reliable globally.