Side Channel Attacks: Your Device Data Is Leaking

By Vijay Kumar Sanugondla, Embedded Engineer at EurthTech

When we think about security in embedded systems, our minds go straight to encryption protocols, secure bootloaders, or maybe tamper detection mechanisms. But what if your device is leaking secrets—not through firmware, but through electricity, timing, or even RF noise?

Welcome to the world of side-channel attacks—where the attacker doesn’t break your cryptography, they simply listen to how your hardware executes it.

In this blog, we explore how these attacks work, why even certified systems are vulnerable, and how we—as embedded engineers—can design with better defense in mind.

Side-Channel Attacks: The Invisible Threat

At their core, side-channel attacks don’t exploit code—they exploit behavior. Every time a microcontroller performs an operation, it leaves traces: changes in power consumption, electromagnetic emissions, response times, even heat or light patterns.

These leaks can be subtle—often invisible during normal operation—but under the right tools, they’re like footprints in fresh snow.

Let’s take a familiar example: a smart card performing AES encryption. You might assume it’s secure. But using Differential Power Analysis (DPA), an attacker can collect hundreds of power traces while encryption is happening. By comparing how power consumption varies based on input data, they can statistically reverse-engineer the encryption key.

In our lab, we’ve simulated similar attacks on off-the-shelf wearable and access control systems—and in many cases, the weakest link wasn’t the algorithm, it was the hardware.

Real-World Breaches We've Studied

Smart Locks: Timing-Based Key Recovery

In one product teardown, a BLE-based smart lock implemented a custom challenge-response protocol. Researchers found that the device’s response time varied slightly depending on the bit patterns in the challenge. Using repeated requests and microsecond-level timing analysis, they reconstructed parts of the secret key—without touching the firmware.

Medical Wearables: EM Leakage

Another project involved analyzing a glucose monitoring system that transmitted encrypted data wirelessly. We placed near-field EM probes close to the chip and noticed repeatable emission patterns during data transmission. With EM analysis, it was possible to infer internal processing states of the encryption engine.

Industrial IoT Controllers: Power Correlation

In a factory-deployed controller using ECC to sign messages, we used high-speed oscilloscopes to capture power usage during signing. Applying correlation techniques to this data revealed enough to begin reconstructing private key material. A few hours of analysis exposed a vulnerability that could compromise the entire industrial control network.

These attacks don’t require firmware access, network exploits, or physical tampering—they only need a window into how your silicon breathes.

Why Embedded Devices Are Especially Vulnerable

Ironically, the very design decisions we make to improve power efficiency in IoT devices can make side-channel analysis easier:

• Predictable sleep/wake cycles make power analysis more deterministic.

• Low-noise power rails amplify signal-to-noise ratio during crypto operations.

• Cost-optimized unshielded PCBs leak more EM signals into the air.

Most developers never think to design against these channels, because unlike memory leaks or firmware bugs, side channels don’t crash your code—they whisper behind your back.

Classes of Side-Channel Attacks: An

We often group SCAs by the kind of leak they exploit:

• Simple Power Analysis (SPA): Visual examination of current traces during operations—can reveal patterns like number of loop iterations, PIN entry logic, or conditional branches.

• Differential Power Analysis (DPA): Statistical analysis of multiple power traces to extract keys from crypto engines like AES or RSA.

• Timing Attacks: Exploiting variations in execution time of authentication routines to learn secret information.

• Electromagnetic Analysis (EMA): Using near-field probes to capture RF emissions during sensitive operations, which correlate with processor activity.

Each method has its own tools and complexity—but all of them are real, and many are inexpensive to perform.

Defending Against Side-Channel Attacks

Side-channel resistance isn’t about a single fix—it’s a layered defense that spans hardware, firmware, and validation.

Hardware-Level Countermeasures:

• Shielding and Filtering: Metal cans, ferrite beads, and careful grounding to limit EM leakage.

• Constant-Time Crypto Accelerators: Use hardware blocks that complete operations in fixed cycles, regardless of input.

• Randomized Clocking: Introduce jitter or pseudo-randomness in clock edges to prevent synchronization.

• Power Line Balancing: Implement dual-rail logic or use matched capacitive loads to obscure signature power traces.

Firmware Techniques:

• Constant-Time Algorithms: Avoid code branches or timing differences based on secret values.

• Dummy Computations: Insert fake logic paths to obfuscate real execution flows.

• Random Delays and Obfuscation: Inject non-determinism in function timings.

• Secure Key Handling: Use hardware-based secure elements (TPMs, Secure Enclaves) wherever possible.

Testing and Validation:

Before any deployment, your lab should simulate what an attacker might do:

• Oscilloscopes and Power Profilers for trace capture

• Near-Field EM Probes for emission sniffing

• Analysis Platforms like ChipWhisperer to run DPA or correlation models

At EurthTech, we include these tests in our Security Review Suite for critical firmware clients—especially for medical, automotive, and access control projects.

Certifications That Include Side-Channel Protection

Security certifications are beginning to recognize SCAs as a mainstream threat. For sensitive or regulated devices, consider alignment with:

Certification	Focus	SCA Protection?
FIPS 140-3	Cryptographic modules	Yes – EM + physical
Common Criteria (EAL4+)	Secure embedded systems	Yes – includes side-channel evaluations
EMVCo	Payment terminals	Yes – essential for smart cards & NFC

If you’re aiming for medical, defense, payment, or industrial certifications, this isn’t optional anymore—it’s expected.

Designing for Side-Channel Resistance from Day One

The worst mistake you can make is to treat security as something you patch later. SCAs don’t wait for your firmware updates—they live in your physical design and in your signal integrity choices.

Build defense into your architecture:

• Pick MCUs with hardware crypto accelerators and shielding options.

• Isolate secure functions in code and layout.

• Reduce trace lengths and avoid unintentional antennas in PCB layout.

• Simulate attacker profiles during system validation—not after first release.

In one EurthTech audit, we found that simply moving the antenna away from the crypto section of the board reduced EM leakage by 80%. That’s the kind of fix that can’t be patched later.

Final Thoughts: Security You Can’t Ignore

Side-channel attacks are a silent but growing threat. They bypass firewalls, certificates, and firmware controls—not through hacking, but through listening.

As embedded systems engineers, we need to think beyond code and protocols. We must secure the physics. Whether you're building wearables, secure modules, or factory gateways, side-channel defense is no longer advanced—it’s essential.

At EurthTech, our embedded security services help companies build systems that don’t just work—but hold their ground when probed, analyzed, and attacked.

💬 Have a design that handles sensitive data?

📩 Let’s run it through our Embedded Security Checklist — before someone else runs theirs.