How Does HTTPS Work? Step-by-Step Guide to Secure Web Communication (2025)

Learn how HTTPS works, from TLS handshakes to encryption methods. Understand how data is encrypted, decrypted, and transmitted securely across the internet in this simplified 2025 guide.

Network Security May 26, 2025 58 Add to Reading List

How Does HTTPS Work? Step-by-Step Guide to Secure Web Communication (2025)

What Is HTTPS and How Is It Different from HTTP?
Step-by-Step: How HTTPS Works
Why HTTPS Switches to Symmetric Encryption
HTTPS vs HTTP: Performance Overhead
What Happens If HTTPS Is Not Used?
Does HTTPS Mean a Website Is Safe?
How Does a Browser Show HTTPS Is Active?
Is TLS 1.3 Better Than TLS 1.2?
Conclusion
Frequently Asked Questions (FAQs)

In today’s internet-driven world, privacy and security are not optional — they are essential. Whether you're shopping online, logging into your bank, or submitting a form, your data needs to be protected from prying eyes. That’s where HTTPS (Hypertext Transfer Protocol Secure) comes in. It secures data transmission over the web using a combination of TLS (Transport Layer Security) and cryptographic protocols.

But how exactly does HTTPS work under the hood? What makes it secure, and why is it the standard for all modern websites? Let’s break it down step by step.

What Is HTTPS and How Is It Different from HTTP?

HTTPS is the secure version of HTTP. While HTTP transmits data in plain text, HTTPS uses encryption to protect data from interception. This encryption is made possible through TLS (formerly SSL) — ensuring that even if data is intercepted, it is unreadable.

Protocol	Encryption	Security Level
HTTP	No	Low (Vulnerable to MITM)
HTTPS	Yes (TLS)	High (Encrypted, Authenticated)

Step-by-Step: How HTTPS Works

Here’s a breakdown of what happens behind the scenes when you visit a website using HTTPS:

Step 1: Establishing a TCP Connection

Before any encryption begins, the client (browser) and server initiate a TCP (Transmission Control Protocol) connection. This step sets the foundation for further secure communication.

Step 2: TLS Handshake – Client Hello & Server Hello

Once connected, the client sends a "Client Hello" message to the server, which includes:

Supported TLS versions
List of cipher suites (encryption algorithms)
A random number
Optional extensions like Server Name Indication (SNI)

The server responds with a "Server Hello", choosing:

The TLS version and cipher suite
Another random number
SSL/TLS certificate (contains domain, public key, issuer, expiry date)

This handshake lets both parties agree on how to encrypt the connection.

Step 3: SSL/TLS Certificate Validation

The client validates the server's certificate using:

Certificate Authority (CA) verification
Checking hostname, expiry date, and digital signature

If everything checks out, the browser trusts the server and continues to establish encryption.

Step 4: Session Key Exchange via Public-Key Cryptography

Once the certificate is validated:

The client creates a session key (a random symmetric key)
It encrypts the session key using the server’s public key
The server uses its private key to decrypt the session key

This establishes a shared secret between both parties.

Step 5: Secure Communication Using Symmetric Encryption

With the shared session key, both client and server now:

Encrypt and decrypt data symmetrically
Exchange data over a bi-directional, secure channel

Symmetric encryption is fast and efficient — ideal for sustained communication during web sessions.

Why HTTPS Switches to Symmetric Encryption

Though asymmetric encryption is more secure for the initial handshake, it's not practical for long sessions. Here's why HTTPS switches to symmetric encryption post-handshake:

1. Performance Optimization

Asymmetric encryption is computationally expensive, increasing load on servers during prolonged exchanges. Symmetric encryption, on the other hand, is light and fast.

2. Bidirectional Encryption

Asymmetric encryption is mostly one-way. It encrypts with the public key but can only be decrypted by the private key. Symmetric encryption allows both ends to encrypt and decrypt, supporting two-way communication.

HTTPS vs HTTP: Performance Overhead

Yes, HTTPS is slightly heavier than HTTP due to:

TLS handshake overhead
Certificate validation
Cryptographic computations

However, modern TLS versions (like TLS 1.3) have reduced this significantly. According to benchmarks:

The initial load time might be ~10ms slower on average
After that, session resumption eliminates handshake delays
Browsers and CDNs cache certificates, minimizing repeated work

Bottom Line: The performance cost is minimal and negligible compared to the security gains.

What Happens If HTTPS Is Not Used?

Without HTTPS:

Passwords, payment data, personal info are sent in plain text
Anyone on the same network can intercept and read the data
Users are vulnerable to man-in-the-middle (MITM) attacks
Google Chrome flags such sites as “Not Secure,” reducing trust

Does HTTPS Mean a Website Is Safe?

Not necessarily.

HTTPS ensures secure data transmission, but it doesn't validate what the website does with your data. A phishing site can still use HTTPS to look legitimate. Hence, always look at:

Domain name correctness
SSL certificate validity
The website’s reputation and reviews

How Does a Browser Show HTTPS Is Active?

When a secure HTTPS connection is established, browsers display:

Padlock icon in the address bar
HTTPS in the URL
Sometimes, the organization name for EV certificates

You can click the padlock to view certificate details.

Is TLS 1.3 Better Than TLS 1.2?

Yes. TLS 1.3:

Reduces handshake time (1 round trip instead of 2)
Removes outdated algorithms (like SHA-1, RC4)
Increases privacy by encrypting more parts of the handshake

All modern browsers and servers now support TLS 1.3 by default.

Conclusion: Why HTTPS Matters More Than Ever

In the age of digital privacy, HTTPS is no longer optional — it’s mandatory. It not only protects user data from prying eyes but also builds trust, search ranking, and credibility for websites. From online banking to casual browsing, HTTPS ensures your connection is private and authenticated.

As attackers evolve, HTTPS and its underlying TLS encryption protocols continue to adapt — giving users and developers the confidence that the web can be a safer place for all.

FAQs

What is HTTPS and why is it important?

HTTPS (Hypertext Transfer Protocol Secure) is essential for secure web browsing. It encrypts data between the client and server using TLS, protecting sensitive information from being intercepted.

How does HTTPS encrypt data?

HTTPS uses asymmetric encryption during the handshake and switches to symmetric encryption for actual data transfer. This ensures fast and secure communication.

What is a TLS handshake?

A TLS handshake is the process where the client and server exchange cryptographic information to establish a secure connection using a shared session key.

What is the difference between symmetric and asymmetric encryption?

Symmetric encryption uses one shared key for both encryption and decryption, while asymmetric encryption uses a public key to encrypt and a private key to decrypt.

Why does HTTPS use symmetric encryption after the handshake?

HTTPS uses symmetric encryption post-handshake because it's faster and more efficient for ongoing data transmission, reducing server load and latency.

How does a browser validate an SSL certificate?

A browser validates an SSL certificate by checking its digital signature, expiration date, issuing Certificate Authority (CA), and domain name matching.

Is HTTPS completely secure?

HTTPS provides strong encryption, but it doesn’t guarantee a website is safe from phishing or malware. Always verify the domain and site reputation.

Does HTTPS affect website performance?

While HTTPS adds a slight performance overhead due to encryption, modern TLS protocols like TLS 1.3 have optimized performance to negligible levels.

How can I check if a website uses HTTPS?

Look for a padlock icon in the address bar and “https://” at the start of the URL. Clicking the padlock reveals certificate information.

What is a digital certificate in HTTPS?

A digital certificate verifies the server’s identity. It includes the domain name, public key, issuer, and validity dates, signed by a trusted Certificate Authority.

Can HTTPS prevent man-in-the-middle attacks?

Yes, HTTPS encrypts communication, preventing attackers from intercepting or altering data in transit, which is key to avoiding man-in-the-middle (MITM) attacks.

What happens if a website doesn't use HTTPS?

Without HTTPS, data is sent in plain text and is vulnerable to interception, especially on public Wi-Fi or untrusted networks.

How is the session key generated in HTTPS?

The session key is randomly generated by the client and encrypted with the server’s public key during the handshake, then decrypted by the server.

What is the role of the Certificate Authority (CA)?

CAs issue SSL/TLS certificates and vouch for the authenticity of the domain, ensuring the website owner is verified and trustworthy.

What are cipher suites in HTTPS?

Cipher suites are combinations of encryption algorithms used to secure communication in TLS/HTTPS connections.

What version of TLS is currently recommended?

TLS 1.3 is the latest and most secure version, offering improved speed, stronger encryption, and better privacy than previous versions.

Is HTTPS mandatory for all websites?

While not legally required, HTTPS is strongly recommended. Search engines penalize non-HTTPS sites, and browsers mark them as "Not Secure."

Can HTTPS be used on mobile apps and APIs?

Yes, HTTPS is widely used in mobile applications and APIs to ensure secure client-server communication.

What is HTTPS Everywhere?

HTTPS Everywhere is a browser extension that forces websites to use HTTPS if available, improving security by default.

How do hackers bypass HTTPS?

While HTTPS is secure, hackers can exploit weaknesses like expired certificates, DNS spoofing, or phishing with valid certificates.

Can HTTPS be trusted on public Wi-Fi?

Yes, HTTPS secures your data even on public Wi-Fi, as long as you verify the certificate and domain before entering sensitive information.

What is forward secrecy in HTTPS?

Forward secrecy ensures that session keys are not compromised even if a server’s private key is later exposed. It's a feature in modern TLS configurations.