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STATUS_BTH_ATT_INSUFFICIENT_AUTHENTICATION
Authentication requirements, not merely an unavailable attribute
STATUS_BTH_ATT_INSUFFICIENT_AUTHENTICATION is ATT error 0x05. The server has identified the target attribute and requires a security state that the current connection does not satisfy.
Do not equate this mechanically with “not encrypted.” Bluetooth distinguishes authentication, encryption, and encryption-key-size conditions. The Generic Access Profile also notes that the interpretation depends on the existing link state: an encrypted link with an unauthenticated pairing can still fail an operation that requires stronger protection.
What to check
- Keep the ATT opcode and handle with the pairing or bond state, encryption state, authenticated-pairing requirement, and any user-interaction result.
- Determine the attribute's required security level from the device profile or firmware, then initiate the appropriate pairing or reconnection flow instead of retrying the same ATT request blindly.
- Do not treat this as an authorization policy result; authorization is reported separately by ATT error 0x08.
References
- Bluetooth SIG: Attribute Protocol (ATT)
- Bluetooth SIG: Generic Access Profile security requirements
- Microsoft: Bluetooth GATT client
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