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E_BLUETOOTH_ATT_INSUFFICIENT_AUTHENTICATION
Encryption can be active without satisfying authentication
E_BLUETOOTH_ATT_INSUFFICIENT_AUTHENTICATION is ATT error 0x05. In Bluetooth security terminology, authentication usually concerns the assurance established by pairing, including whether the association method provides man-in-the-middle protection. A link encrypted with an unauthenticated key can therefore still be rejected.
The correct response depends on the attribute security requirements and the capabilities of both devices. Reconnecting with the same bond does not strengthen it. The client may need to remove and recreate the bond using passkey entry, numeric comparison, or another association model accepted by the peripheral.
How to diagnose the security mismatch
- Record whether the link is merely encrypted or also authenticated at the required security level.
- Check the I/O capabilities that selected the pairing association model.
- Remove stale bonds on both peers before testing a different pairing method.
- Distinguish this code from Insufficient Authorization, which represents a server policy decision after identity is known.
References
- Bluetooth Core: Security Manager and association models
- Bluetooth Core: Insufficient Authentication
- Apple Core Bluetooth: ATT security errors
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