HTTP vs HTTPS vs SSL/TLS: A Comprehensive Guide to Web Security Protocols (with HTTPS Deployment Steps)

Have you ever noticed the difference between “http://” and “https://” when typing a URL? What does the small lock icon next to the address bar signify when you make a payment on an e-commerce platform or log into a social media account? In internet communications, terms like HTTP, HTTPS, and SSL/TLS appear frequently—they are not only core technologies safeguarding network security but also “barometers” for ordinary users to perceive online safety.

This guide will break down the relationships and functions of these technologies from the perspectives of protocol essence, working mechanisms, and security logic. It also includes practical HTTPS deployment steps, helping developers, website owners, and tech enthusiasts decode the “security passwords” behind web communications.

I. HTTP: The “Bare” Foundation of Internet Data Transmission

HTTP (Hypertext Transfer Protocol), proposed by Tim Berners-Lee in 1990, is a core protocol in the application layer of the TCP/IP model. It lays the groundwork for web resource transmission as a stateless request-response protocol, defining interaction standards between clients (e.g., browsers) and servers—similar to a standardized “data communication template.” However, security mechanisms were not integrated into its initial design, leaving data transmission in a “plaintext exposed” state.

1.1 The “Request-Response” Workflow of HTTP (Taking Access to www.example.com as an Example)

1. Request Message Construction: After entering a URL, the browser encapsulates an HTTP request message, consisting of a request line (e.g., “GET /index.html HTTP/1.1”), request headers (e.g., “User-Agent: Mozilla/5.0”, “Cookie: sessionid=xxx”), and an optional request body (carrying form data for POST requests).
2. TCP Connection Establishment: HTTP relies on the reliable transmission service provided by TCP. The client establishes a connection with the server’s port 80 through a three-way handshake (“SYN→SYN-ACK→ACK”) to ensure the order and integrity of data transmission.
3. Server Response Processing: Upon receiving the request, the server executes corresponding business logic (e.g., database queries, static resource reading) and generates a response message. This includes a status line (e.g., “HTTP/1.1 200 OK”), response headers (e.g., “Content-Type: text/html; charset=utf-8”, “Content-Length: 1024”), and a response body (resources like HTML, CSS, and JS).
4. Connection Release and Rendering: The browser parses the response body and completes DOM rendering. If the Keep-Alive persistent connection mechanism of HTTP/1.1 is not enabled, TCP releases the connection through a four-way handshake (“FIN→ACK→FIN→ACK”), requiring a new connection for each subsequent request.

1.2 Three Fatal Flaws of HTTP (Still Plaguing Some Websites Today)

• Plaintext Transmission Risk: All communication data is transmitted in ASCII plaintext. Attackers can intercept data packets through ARP spoofing, router sniffing, or other methods to directly extract sensitive information. For example, unencrypted HTTP login requests can be captured by Wireshark on public WiFi, leading to the leakage of account passwords.
• Lack of Identity Authentication: The HTTP protocol has no mechanism to verify server identity. Attackers can launch man-in-the-middle attacks by hijacking DNS or setting up fake servers. In a phishing incident, attackers forged a bank’s HTTP website, resulting in the leakage of bank card information from thousands of users.
• Compromised Data Integrity: Without a data verification mechanism, attackers can tamper with HTTP messages in transit. For instance, in e-commerce scenarios, an attacker could modify the “Price” field in the response message from $1999 to $99, causing economic losses to the merchant.

⚠️ Key Note: Major browsers like Chrome and Firefox now forcibly mark HTTP websites as “Not Secure,” and Google Search significantly demotes their rankings—using HTTP for website building no longer holds practical value in modern web environments.

II. SSL/TLS: The “Security Shield” of HTTPS, Current Mainstream Algorithms

To address HTTP’s security vulnerabilities, Netscape launched the SSL (Secure Sockets Layer) protocol in 1994. After iterations through SSL 2.0 and 3.0, the IETF standardized it as the TLS (Transport Layer Security) protocol in 1999. Currently, TLS 1.2 remains the most widely compatible base version, while TLS 1.3 has become the optimal choice for performance and security due to optimized handshake processes (reduced from 4 to 2 interactions) and upgraded cipher suites (removing weak algorithms like 3DES and RC4). TLS 1.0 and 1.1 have been fully deprecated by major browsers and server vendors due to security vulnerabilities such as BEAST and POODLE.

2.1 Core Technology: The “Golden Combination” of Symmetric and Asymmetric Encryption

SSL/TLS’s essence lies in combining the advantages of two encryption algorithms to balance “security” and “efficiency”:

Collaboration Logic: SSL/TLS adopts a hybrid architecture of “asymmetric encryption for key exchange + symmetric encryption for data transmission.” During the handshake phase, asymmetric encryption (e.g., ECC) is used to securely distribute the “pre-master secret,” preventing key interception in transit. After the handshake, both parties generate a session key (symmetric key) based on the pre-master secret and random numbers. All subsequent application-layer data is encrypted using symmetric algorithms like AES-256-GCM, balancing security and transmission efficiency.

2.2 TLS 1.3 Handshake Process (Optimized Version with Only 2 Interactions)

The handshake is the core of SSL/TLS for establishing a secure connection. TLS 1.3 simplifies steps compared to TLS 1.2, significantly improving access speed:

1. Client Hello: The client sends a message to the server containing a list of supported TLS versions (e.g., TLS 1.3/TLS 1.2), supported cipher suites (e.g., TLS_AES_256_GCM_SHA384, TLS_CHACHA20_POLY1305_SHA256), a 32-byte client random number, and extension fields (e.g., ALPN protocol negotiation).
2. Server Hello + Certificate + Key Exchange: After selecting the optimal configuration, the server returns a Server Hello message (confirming the TLS version and cipher suite), a digital certificate (issued by a trusted CA, containing the server’s public key, domain name, validity period, etc.), and key exchange parameters (e.g., ECDHE ephemeral public key). The client verifies the validity of the certificate chain using built-in CA root certificates; if verification fails, a browser security warning is triggered.
3. Key Derivation and Verification: The client encrypts the “pre-master secret” with the server’s public key, then generates a master key using the HKDF (Key Derivation Function) combined with the client random number and server random number. It further derives a session key (for data encryption) and a MAC key (for integrity verification).
4. Handshake Finished: Both parties encrypt a “Finished” message using the session key, which contains a hash of all messages during the handshake. If the receiver decrypts the message and the hash values match, the handshake is confirmed successful, and the secure channel is officially established.

2.3 Essential Differences Between SSL/TLS Handshake and TCP Three-Way Handshake

In simple terms: The TCP three-way handshake “builds a road,” while the SSL/TLS handshake “installs door locks and monitoring on the road.”

III. HTTPS: The Secure Upgrade of HTTP, From Principles to Deployment

HTTPS (HTTP Secure) is a security-enhanced version of the HTTP protocol. By inserting an SSL/TLS encryption layer between HTTP and TCP, it achieves confidentiality, integrity, and identity authentication of application-layer data. It uses port 443 by default and follows an architecture of “encrypted tunnel + plaintext protocol”—SSL/TLS handles underlying encrypted data transmission, while HTTP manages upper-layer application logic interactions. Together, they form the security standard for modern web communications.

3.1 Why HTTPS Is Indispensable Today: Four Core Values

• Privacy Protection: Sensitive user data such as login credentials and payment information is transmitted encrypted. Even if intercepted, the data cannot be decrypted.
• Trust Endorsement: Verifies website identity through digital certificates issued by trusted CAs (Certificate Authorities), eliminating phishing sites.
• SEO Advantage: Google lists HTTPS as a ranking signal. Under the same conditions, HTTPS websites receive over 30% more traffic than HTTP sites.
• Compliance Requirements: Regulations such as the EU’s GDPR and China’s Personal Information Protection Law mandate HTTPS for processing sensitive data. Violations can result in fines of up to 4% of global annual turnover.

3.2 Full HTTPS Communication Process (From URL Entry to Webpage Rendering)

1. The browser initiates a TCP three-way handshake to the server’s port 443 to establish a basic connection.
2. Both parties perform a TLS 1.3 handshake to negotiate encryption rules and generate a session key.
3. The browser sends an encrypted HTTP request (e.g., GET /index.html).
4. The server decrypts the request with the session key, processes it, and returns an encrypted HTTP response.
5. The browser decrypts the response, parses it, and renders the webpage.
6. After data transmission is complete, SSL/TLS closes the secure connection, and TCP releases the connection through a four-way handshake.

3.3 Practical HTTPS Deployment Guide (Beginner-Friendly)

💡 Recommended Tools: Let’s Encrypt (free certificates), Certbot (automated deployment), Nginx/Apache (server configuration)

1. Certificate Application and Verification: Use an ACME protocol client (e.g., Certbot) to connect to Let’s Encrypt and verify domain ownership through DNS-01 or HTTP-01 challenges. For DNS verification, add a TXT record to domain resolution; for HTTP verification, place a specific verification file on the server. Once verified, you can obtain PEM-format files containing the certificate chain (server certificate, intermediate certificate) with a 90-day validity period. Configure a crontab task for automatic renewal (e.g., “0 0 1 * * certbot renew”).
2. Server Configuration Optimization: For Nginx, in addition to basic SSL configuration, add security enhancements:plaintextssl_protocols TLSv1.2 TLSv1.3; ssl_prefer_server_ciphers on; ssl_ciphers "EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH"; ssl_session_cache shared:SSL:10m; ssl_session_timeout 10m; Here, ssl_protocols explicitly disables older TLS versions, and ssl_ciphers prioritizes forward secrecy algorithms.
3. HSTS and Redirect Configuration: Add an HSTS response header in the Nginx configuration and set up a 301 permanent redirect from HTTP to HTTPS:plaintextserver {listen 80; server_name example.com; return 301 https://$host$request_uri;} add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always; HSTS forces browsers to use HTTPS directly for subsequent visits, preventing SSL stripping attacks.
4. Post-Deployment Testing and Tuning: Use the SSL Labs Test tool for a security score, aiming for an A+ rating. Common optimization points include enabling OCSP Stapling to reduce certificate verification time, configuring HTTP/2 to improve concurrency performance, and disabling SSL session tickets to avoid key reuse risks.

IV. Common Misconceptions: Pitfalls to Avoid with HTTPS

Q1: Does HTTPS Use Asymmetric Encryption for All Data Transmission?

No. Asymmetric encryption is only used to exchange keys during the handshake phase. Actual data transmission relies on symmetric encryption—using asymmetric encryption for all data would slow down webpage loading by more than 10 times due to its low speed.

Q2: Is HTTPS 100% Secure?

No. HTTPS security depends on end-to-end secure configuration, with three key risk points requiring careful prevention:

• Certificate Trust Chain Issues: Self-signed certificates or incorrectly configured intermediate certificates will cause browsers to distrust the site. A company once experienced a 4-hour HTTPS service outage in 2024 due to an expired intermediate certificate.
• Vulnerable Cipher Suites: Websites using TLS 1.0 or RC4 algorithms are prone to cracking. An e-commerce platform in 2024 suffered a data breach affecting 100,000 users due to enabling weak cipher suites.
• Configuration Defects: Not enabling HSTS may expose the site to SSL stripping attacks, while an incomplete certificate chain increases verification time.Regular security scans (e.g., using OpenVAS) and configuration audits are necessary to ensure the HTTPS environment complies with OWASP security standards.

Q3: Are Free Certificates Less Secure Than Paid Ones?

No difference in security. Free certificates from Let’s Encrypt offer the same encryption strength as paid certificates from Symantec. The only differences are that paid certificates provide enterprise identity verification (EV certificates) and technical support—free certificates are sufficient for personal blogs or small-to-medium enterprises.

V. Conclusion: The Evolution and Future of Web Security Protocols

The evolution from HTTP to HTTPS reflects the transformation of internet security architecture from “function-first” to a “zero-trust” model. As quantum computing technology advances, post-quantum cryptography (PQC) has begun to integrate with the TLS protocol. NIST-recommended algorithms like CRYSTALS-Kyber are gradually becoming standard for key encapsulation to defend against future quantum computing attacks on RSA/ECC algorithms.

For enterprises and developers, HTTPS is not only a compliance requirement but also a core infrastructure for building user trust and ensuring business continuity. A regular security operation and maintenance mechanism should be established, including certificate lifecycle management, encryption algorithm upgrades, and security vulnerability response, to maintain communication security amid technological iterations.

The next time you see the small lock icon in your browser’s address bar, remember: it represents a security barrier jointly constructed by TCP/IP’s reliable transmission, SSL/TLS’s encryption protection, and HTTP’s application interaction. Whether building a website or browsing the web, security is always the top priority of the internet.