Blog | G5 Cyber Security

BLE Secure Connections

G5 Cyber Security

TL;DR

This guide shows you how to set up a secure connection using Bluetooth Low Energy (BLE) 4.2 or later. We’ll focus on the key steps for pairing and encrypting communication, making your BLE devices much safer.

Setting Up Secure Connections

  1. Understand the Basics: BLE security relies on several technologies:
    • Pairing: Establishing a trusted relationship between two devices.
    • Encryption: Scrambling data so it can’t be read by others.
    • Bonding: Storing pairing information for future connections (optional, but recommended).
  2. Check Hardware and Software Support: Make sure both your BLE devices support Bluetooth 4.2 or later. This is essential for Secure Connections.
    • Most modern smartphones and development boards (like Nordic nRF52 series, ESP32) do.
    • Verify the chipset documentation.
  3. Implement Pairing: The pairing process involves exchanging security information.
    1. Initiate Pairing: One device (the initiator) starts the connection request. This is usually done through a user interface button or automatically when devices come into range.
    2. Exchange Security Keys: The devices exchange random numbers and use them to generate shared keys. 
      // Example - simplified pairing initiation (pseudocode)
bledata.startPairing();
    3. Confirm Pairing: Both devices need a way to confirm the pairing is legitimate. This can be done with:
      • Passkey Entry: A user enters a code displayed on both screens.
      • Just Works Pairing: No confirmation needed (less secure, use only for trusted environments).
      • Numeric Comparison: Devices display numbers and the user confirms they match.
  4. Enable Encryption: Once paired, encryption should be automatically enabled.
    • BLE uses AES-CCM encryption for secure data transfer.
    • Ensure your BLE stack is configured to use encryption after pairing.
    // Example - enable encryption (pseudocode)
bledata.enableEncryption();
  5. Implement Bonding (Recommended): Bonding stores the security keys so you don’t have to pair every time.
    1. Store Keys Securely: The keys must be stored in a secure location on both devices, like flash memory with protection against unauthorized access.
    2. Retrieve Keys: When reconnecting, the devices can use the stored keys to re-establish the connection without repeating the pairing process. 
      // Example - bonding (pseudocode)
bledata.bond(); // Store security information
bledata.restoreBondedDevice(); // Retrieve from storage on reconnection
  6. Security Considerations:
    • Man-in-the-Middle Attacks: Be aware of potential attacks where an attacker intercepts the pairing process. Use strong authentication methods (passkey entry or numeric comparison).
    • Key Storage Security: Protect the stored keys from being compromised.
    • Regular Updates: Keep your BLE stack and firmware up to date to benefit from security patches.
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