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E_BLUETOOTH_ATT_INSUFFICIENT_ENCRYPTION
The request reached the attribute before link security was established
E_BLUETOOTH_ATT_INSUFFICIENT_ENCRYPTION maps ATT error 0x0F. The server policy allows access only after link-layer encryption is enabled. The devices may be unpaired, may have lost their bond, or may be connected before the host has initiated encryption using stored keys.
This code should not be conflated with Insufficient Authentication or Insufficient Encryption Key Size. Encryption may solve this specific error, but an authenticated association or a longer key can still be required by the same attribute on the next attempt.
Check the connection security transition
- Observe whether pairing or encryption starts before the protected GATT operation.
- Verify that both peers retain matching bond information and keys.
- Wait for the platform security procedure to complete before retrying the read or write.
- If encryption repeatedly drops, investigate the link and bond state rather than changing attribute permissions.
References
- Bluetooth Core: LE encryption and bonding
- Bluetooth Core: Insufficient Encryption
- Microsoft: Windows Bluetooth LE APIs
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