ESP32 is one of the most popular microcontrollers in the IoT world, mainly because it combines strong processing power with built-in WiFi and Bluetooth at a very affordable cost. Beginners often focus on getting WiFi connectivity working as quickly as possible, but security is usually ignored in early projects. Unfortunately, insecure ESP32 devices are easy targets for attackers and can lead to data leaks, unauthorized control, or even large-scale botnet abuse.

This blog is a beginner-friendly yet deep dive into ESP32 WiFi security. We will cover how WiFi communication works on ESP32, common attack vectors, firmware security basics, encryption, secure OTA updates, and practical steps you can apply today. Even if you are new to embedded systems, this guide will help you build safer ESP32-based IoT devices.

Why ESP32 WiFi Security Matters

Every ESP32 connected to WiFi becomes part of a network. That network could be your home, your office, or a production environment. Once connected to the internet, your device is exposed to:

• Unauthorized access attempts
• Packet sniffing
• Man in the middle attacks
• Firmware tampering
• Credential theft
• Remote command injection

Many real-world IoT attacks happened not because the hardware was weak, but because security was never enabled. ESP32 actually provides strong security features, but they must be configured correctly.

How ESP32 Connects to WiFi (Beginner Overview)

Before securing WiFi, it is important to understand how the ESP32 connects.

Basic WiFi flow:

• ESP32 scans for available networks
• It authenticates using the SSID and password
• It obtains an IP address via DHCP
• It starts sending and receiving data

A simple ESP-IDF example looks like this:

wifi_config_t wifi_config = {    .sta = {        .ssid = "MyWiFi",        .password = "mypassword",    },};esp_wifi_set_mode(WIFI_MODE_STA);esp_wifi_set_config(WIFI_IF_STA, &wifi_config);esp_wifi_start();

This works, but it is not secure by default.

Common WiFi Security Mistakes Beginners Make

Understanding mistakes helps you avoid them.

1. Hardcoding WiFi Credentials

Hardcoding the SSID and password in the firmware makes extraction easy if someone reads the flash.

2. Using Open or Weak WiFi Networks

Open networks or WEP-based networks offer almost no protection.

3. No Encryption for Data Transfer

Sending data over HTTP instead of HTTPS exposes it to sniffing.

4. Disabling Certificate Verification

Many beginners disable TLS verification to fix connection errors, which defeats security entirely.

5. No OTA Security

Unsigned OTA updates allow attackers to install malicious firmware.

WiFi Network Security Basics for ESP32

Use WPA2 or WPA3 Only

Always connect ESP32 devices to networks secured with WPA2 or WPA3. Avoid open networks in production environments.

Avoid Reusing WiFi Credentials

If possible, use device provisioning instead of embedding credentials permanently.

Secure WiFi Provisioning

Better provisioning methods include:

• BLE based provisioning
• Temporary Access Point with one-time password
• QR code-based provisioning

ESP-IDF provides a secure WiFi provisioning framework that encrypts credentials during setup.

Official documentation: docs.espressif.com

Securing ESP32 Firmware Basics

WiFi security is useless if the firmware itself is compromised.

Secure Boot

Secure Boot ensures only trusted firmware runs on the device. The ESP32 verifies the firmware signature during startup.

Benefits:

• Prevents malicious firmware injection
• Stops unauthorized firmware modification

ESP-IDF Secure Boot docs: docs.espressif.com

Flash Encryption and WiFi Credentials Protection

ESP32 stores WiFi credentials in flash memory. Without flash encryption, anyone with physical access can extract them.

What Flash Encryption Does

• Encrypts firmware stored in flash
• Encrypts WiFi credentials
• Protects API keys and tokens

Once enabled, flash contents are unreadable outside the ESP32.

Flash encryption docs: docs.espressif.com

Secure Communication Over WiFi

Always Use TLS

All data sent over WiFi should be encrypted using TLS.

Protocols to use:

• HTTPS instead of HTTP
• MQTT over TLS instead of plain MQTT

Example HTTPS request using ESP-IDF:

esp_http_client_config_t config = {    .url = "<https://api.example.com/data>",    .cert_pem = server_cert_pem,};esp_http_client_handle_t client = esp_http_client_init(&config);esp_http_client_perform(client);

Certificate Validation Is Mandatory

Never disable certificate verification. If memory is limited, use:

• Certificate pinning
• ECC certificates instead of RSA

Device Identity and Authentication

Every ESP32 device must be uniquely identifiable.

Bad Practice

• One API key shared across all devices

Good Practice

• Unique device ID
• Per device token
• Certificates per device

This prevents one compromised device from affecting others.

OTA Updates and WiFi Security

OTA updates are powerful and dangerous.

Secure OTA Checklist

• Use HTTPS for OTA download
• Verify firmware signature
• Enable rollback protection
• Reject unsigned firmware

ESP-IDF OTA security guide: docs.espressif.com

OTA without signature verification is one of the biggest IoT security risks.

Common ESP32 WiFi Attack Vectors

Man in the Middle Attack

Occurs when data is intercepted between the ESP32 and the server. Prevented by proper TLS validation.

Evil Twin WiFi Attack

The attacker creates a fake WiFi network with the same SSID. Mitigated by WPA2 and certificate validation.

Prevented by flash encryption and disabling debug interfaces.

Replay Attacks

Prevented using timestamps, nonces, and server-side validation.

Logging and Debugging Without Leaking Data

Avoid printing sensitive data in logs.

Never log:

• WiFi passwords
• Tokens
• Certificates

Disable verbose logging in production builds.

Beginner Friendly Security Checklist

Before deploying an ESP32 device:

• Use WPA2 or WPA3 WiFi
• Enable Secure Boot
• Enable Flash Encryption
• Use HTTPS or MQTT over TLS
• Validate certificates
• Secure OTA updates
• Disable debug interfaces
• Use a unique device identity

FAQs (Frequently Asked Questions)

Is ESP32 secure enough for commercial products?

Yes, if Secure Boot, flash encryption, and TLS are properly enabled. Many commercial IoT products use ESP32.

Yes, if flash encryption is disabled. With flash encryption enabled, extraction becomes extremely difficult.

Is HTTPS heavy for ESP32?

HTTPS consumes more memory, but ESP32 hardware acceleration and ECC certificates make it practical for most use cases.

Should beginners enable Secure Boot?

Yes. It is better to learn with security enabled than to add it later.

Is MQTT secure on ESP32?

MQTT itself is not secure, but MQTT over TLS is secure and widely used in IoT.

Can OTA updates be hacked?

Yes, if firmware signatures are not verified. Secure OTA prevents this.

Conclusion

ESP32 WiFi security is not optional anymore. Even beginner projects can become real-world targets once connected to the internet. The good news is that ESP32 provides excellent security features out of the box. By understanding WiFi communication, enabling encryption, securing firmware, and using proper OTA practices, you can build IoT devices that are resilient and trustworthy.

Start with small steps. Enable TLS, protect credentials, and avoid shortcuts. Over time, security will become a natural part of your ESP32 development workflow.

Author: Yasir Nawaz

Embedded Systems and Cyber Security Engineer

Resume:

View my professional resume at sudoyasir.space

Email:

y451rmahar@gmail.com

LinkedIn:

/in/sudoyasir

GitHub:

github.com/sudoyasir

If you found this article helpful, connect with me on LinkedIn or explore my open source projects on GitHub for more ESP32, IoT security, Linux, and embedded systems content.