We started with a BLE integration task.
We ended up reverse-engineering an encrypted security protocol.

Kerong’s BLE smart locks operate nothing like consumer Bluetooth devices.

Why? Because beneath the BLE layer sits a multi-stage security architecture.

It involves many security nuances like encrypted PIN transformation, device authentication handshakes, dynamic session keys, and more.

If any part of the sequence is even slightly wrong, the lock simply refuses to respond.

This article will share details about the technical obstacles encountered while integrating Kerong’s BLE smart lock. Plus, we will also explain how its multi-layer security model transforms a “simple BLE feature” into a full-scale protocol engineering challenge.

Why BLE Smart Locks Are Complex

At first, Kerong’s locks appear to be standard BLE devices.

They advertise, accept connections, and expose characteristics like any other Bluetooth-enabled hardware.

That similarity is where all the illusion ends.

In consumer IoT products, BLE is often used as a convenience layer.

It can send a command, receive a response, and you’re done.

Kerong’s locks, however, treat BLE as nothing more than a transport tunnel for a heavily secured protocol running underneath.

These locks are built for environments where physical access equals operational risk. This includes:

• Industrial lockers
• Self-service kiosks
• Smart city infrastructure
• Secure equipment cabinets

In these scenarios, unauthorized access can lead to asset theft, service disruption, or infrastructure compromise.

As a result, the lock firmware is designed around security enforcement.

Kerong BLE locks incorporate:

• Encrypted PIN-based access control instead of plain credential checks
• Mutual authentication mechanisms to verify both lock and controller
• Session-based encryption that changes across interactions
• Command-level validation where every operation is cryptographically verified

This means you are not “sending a BLE unlock command.”

You are participating in a secure, stateful communication protocol where BLE is simply the carrier.

Understanding this distinction is critical.

Without it, teams approach the integration like a typical BLE project. And it can quickly run into silent failures, rejected commands, and devices that appear connected but never respond.

The Challenge: 4-Layer Security Structure

The biggest misconception during integration was assuming the lock would accept correctly formatted BLE commands once connected.

In reality, Kerong locks enforce a multi-stage security workflow where every command must pass through four tightly controlled layers before the device will execute any physical action.

Miss one step, miscalculate one value, or encrypt one field incorrectly. And the lock simply ignores the request.

1. Device Authentication Handshake

Before any sensitive operation is allowed, the lock validates the identity of the connecting controller.

This is not a simple BLE pairing process.

Instead, the lock expects a structured authentication exchange that proves the client understands the device’s protocol and can participate in secure communication.

Until this handshake succeeds, operational commands are not even considered.

This layer prevents unauthorized apps or rogue BLE devices from directly interacting with the lock.

2. Encrypted Password / PIN Verification

Kerong locks do not accept raw PIN values.

The configured PIN must first be transformed using a proprietary encryption routine.

This encrypted output is then used as part of the authentication sequence.

If the encryption is even slightly off the lock treats the request as invalid.

Because this transformation process is not publicly documented in detail, reproducing it correctly requires deep analysis and careful validation.

3. Session Key Exchange

Once device identity and credentials are validated, the lock establishes a temporary session key.

This key is used to encrypt and decrypt all the communication during the session.

It ensures that even if BLE traffic is intercepted, the commands cannot be replayed or interpreted without the session context.

This step effectively turns the BLE connection into a secure, short-lived encrypted tunnel.

4. Command Authorization & Execution

Only after the previous three layers succeed does the lock evaluate operational commands such as:

• Unlock
• Lock
• Power Off

Each command must be packaged in a precisely structured, encrypted packet that includes session-specific data and validation fields. The lock checks:

• Packet structure
• Encryption correctness
• Session alignment
• Command authorization rules

If any element fails validation, the lock does not return an error code. It simply discards the packet. Quite simple yet so important.

This “silent rejection” behavior is one of the most challenging aspects of integration. Why? Because it provides no direct feedback about what went wrong.

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Sending Secure Commands to the Lock

Once the security architecture was understood, the next challenge was translating it into a working command pipeline.

At this stage, success depended less on BLE knowledge and more on precise protocol implementation.

Sending a single operational command required a strict sequence of transformations and validations before any data was written to the device.

Step 1: Transform the Lock Password Using Kerong’s Encryption

The lock’s PIN could not be used directly.

It first had to be processed through Kerong’s proprietary encryption routine to generate a secure credential representation.

This value became a foundational input for the authentication and session workflow.

Any deviation in how this encryption was performed resulted in total command failure later in the chain.

Step 2: Establish and Apply Session Encryption

After authentication, communication shifted into a session-protected state.

A negotiated session key was used to encrypt command payloads and decrypt responses from the lock.

This meant every outgoing packet had to be encrypted dynamically using session-specific parameters.

Hardcoded or reused payloads would immediately fail validation.

Step 3: Construct the Command Packet at the Byte Level

Commands were not simple opcodes like “0x01 = unlock.”

Each instruction had to be embedded into a structured packet containing:

• Command identifiers
• Length fields
• Encrypted credential data
• Session validation values
• Integrity or checksum bytes

The packet had to match the lock’s expected format exactly. This includes field order, byte alignment, and value encoding all mattered.

A single misplaced byte caused the lock to discard the entire request.

Step 4: Send Through the Correct BLE Characteristic

Even with a perfectly constructed packet, sending it to the wrong BLE characteristic resulted in failure.

The lock exposes multiple services and characteristics, but only specific ones are used for secure command transmission.

Understanding the correct communication channel was just as important as building the packet itself.

Step 5: Handle and Validate the Lock’s Response

When a command was accepted, the lock returned an encrypted response packet. This response also had to be:

• Decrypted using the active session key
• Parsed according to the protocol structure
• Validated to confirm the command executed successfully

Because invalid requests often triggered no response at all, successful integration required building internal validation and logging mechanisms to distinguish between:

• Transmission failures
• Encryption mismatches
• Session desynchronization
• Structurally invalid packets

Why Debugging Was So Difficult

The most time-consuming part of the integration was not sending commands. It was diagnosing why they failed.

Unlike many BLE devices that return error codes, Kerong locks frequently respond to invalid packets with complete silence. No rejection message, no status flag, just no action.

This forced debugging down to the lowest level: inspecting raw packet bytes, verifying encryption outputs, and replaying communication flows until every field matched the lock’s expectations exactly.

Mapping the Challenges to Kerong’s Product Architecture

The integration hurdles weren’t the result of poor design or overengineering.

They stem directly from the type of environments Kerong builds its locking systems for.

Kerong’s products are not consumer smart locks designed for convenience and rapid app integration.

They are components in controlled-access infrastructure. It is exactly where a compromised lock can lead to operational disruption or security breaches.

Their ecosystem spans multiple hardware categories, including:

• Bluetooth cabinet locks
• Passive electronic locks
• NFC-enabled locking systems
• Motor-driven secure latches

Across these product lines, the underlying philosophy is consistent: access control must be cryptographically enforced, not just wirelessly triggered.

Security as a System, Not a Feature

Kerong locks are typically deployed as part of larger managed systems such as:

• Smart locker networks
• Equipment control cabinets
• Public infrastructure terminals
• Distributed asset storage systems

In these use cases, locks are not isolated devices. They are endpoints in a broader security architecture that may include centralized controllers, access management software, and audit systems.

Because of this, their devices incorporate:

• Encrypted PIN storage that prevents credential extraction even if hardware is accessed
• Challenge–response authentication models to verify authorized controllers
• Session-based communication protocols to prevent replay attacks
• Secure electronic key frameworks that tie digital credentials to physical actions

Breakthrough in Integration

After multiple failed command attempts and long debugging cycles, it became clear that high-level assumptions were the problem.

The only way forward was to treat the lock as a closed security protocol and analyze it at the packet level.

Progress began when the integration effort shifted from “trying different commands” to systematically decoding how the lock actually communicates.

Analyzing BLE Traffic

One of the most important steps was capturing and inspecting BLE traffic between the lock and its official control applications. By observing real communication flows, it became possible to identify:

• Authentication sequences
• Encrypted data patterns
• Command packet structures
• Response formats

This provided a reference model for how valid communication was supposed to look.

Reverse-Engineering Encryption Behavior

The next challenge was understanding how the lock transformed credentials and validated commands. By comparing known inputs with observed encrypted outputs, patterns in the encryption workflow began to emerge.

This helped reconstruct:

• The PIN transformation process
• How session keys influenced packet payload
• Which parts of the packet were static vs. dynamically generated

Even small breakthroughs here dramatically improved command success rates.

Rebuilding the Protocol Step by Step

Rather than attempting full commands immediately, the communication flow was rebuilt incrementally:

1. Successfully completing the authentication handshake
2. Verifying encrypted credential acceptance
3. Establishing a stable session key exchange
4. Sending minimally structured test packets
5. Gradually introducing full command payloads

This staged approach made it easier to isolate which layer was causing failures.

Manually Crafting and Testing Command Packets

Automated retries were less useful than deliberate packet construction. Each field in the command structure was validated individually:

• Byte ordering
• Length indicators
• Encryption boundaries
• Integrity or checksum segments

Packets were adjusted and retested until the lock began returning consistent, encrypted acknowledgments instead of silence.

Achieving Reliable Command Execution

Once authentication, encryption, and packet structure were aligned, the lock began responding predictably. Commands such as:

• Unlock
• Lock
• Power Off

executed consistently, and responses could be decrypted and verified within the active session context.

What initially appeared to be an unresponsive BLE device was finally behaving like a secure system that had been correctly understood.

Key Takeaways

Alrigth, we’ll keep this super short. Here’s what you should always keep in mind:

• Enterprise BLE locks are security systems first, Bluetooth devices second
• Commands must pass through multiple encrypted authentication layers
• A single incorrect byte can lead to silent command rejection
• Limited documentation often makes packet-level analysis necessary
• Integrating high-security hardware requires deep protocol and BLE expertise, not just app development skills

Conclusion

What started as a straightforward BLE task quickly turned into a deep dive into secure protocol engineering.

Kerong’s smart locks make one thing clear: in enterprise environments, convenience takes a back seat to security.

Every command, every session, and every byte is treated as a potential risk surface and the device behaves accordingly.

As more infrastructure moves toward smart hardware, integrations like this will become more of the norm.

And if you want to work with teams experienced in IoT app development and Bluetooth Low Energy (BLE) technology, you can get in touch with DevsTree – where secure device communication is built with precision, performance, and reliability.