I use nRF51-DK and nRF51-Dongle for a BLE sniffer.
Always the sniffer fails and marked with an error "Encrypted packet decrypted incorrectly (bad MIC)".
It can not be used for a long time.
From nRF Sniffer User Guide v1.2:
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The Sniffer starts showing “Malformed packets” after a while when sniffing an encrypted link. This is a know limitation with the Sniffer, which will be improved in future releases. See the release notes for details.
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When support improved sniffer ? Please let me know.
Thanks.