Soft Combining Decrypted BLE Packets for CRC Validation
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Solution Overview
Problem
Traditional Bluetooth Low Energy (BLE) protocols lack effective error correction mechanisms to validate the combination of decrypted data packets, especially when transmitted and retransmitted packets are encrypted using different encryption parameters, leading to reduced communication quality and increased power consumption.
Innovation Solution
The proposed solution involves decrypting data packets, soft combining the decrypted payloads, generating a cyclic redundancy check (CRC) based on the soft combined payloads, and determining whether the generated CRC passes a CRC check against a first CRC, thereby validating the combination of transmitted and retransmitted packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional BLE protocol uses retransmission to correct errors, then error correction is achieved, but communication quality deteriorates because packets encrypted with different parameters cannot be validated
Solution Approach 1:
The patent segments the validation process into two independent parts: CRC validation on encrypted packets and MIC validation on decrypted packets. This allows each validation to operate independently without requiring packet matching, thus resolving the issue where different encryption parameters prevent validation. The CRC check validates the encrypted packet integrity while the MIC check validates the decrypted payload integrity, enabling error correction to work effectively across retransmitted packets with different encryption parameters.
2Adaptability or versatility
If retransmitted packets use different encryption parameters, then security and adaptability are improved, but packet validation fails because packets appear different despite having the same payload
Solution Approach 1:
The patent introduces Message Integrity Check (MIC) as an intermediary validation mechanism that operates on the decrypted payload rather than the encrypted packet. The MIC is calculated from the decrypted payload and authentication data, providing a validation layer that is independent of the encryption parameters used. This intermediary approach allows packets with different encryption parameters to be validated correctly, as the MIC validation occurs after decryption when the payload content is what matters, not the encryption parameters used to encrypt it.
3Device complexity
If error correction is not implemented, then device complexity is reduced, but bit error rate increases leading to poor communication quality
Solution Approach 1:
The patent implements preliminary error detection and correction actions by performing CRC validation on received packets before attempting to process the payload. The receiving device validates each received packet using CRC on the encrypted data and MIC on the decrypted data, identifying erroneous packets before they corrupt the communication flow. This preliminary validation enables the system to request retransmission of only the erroneous packets rather than requiring complex forward error correction codes, thus achieving low bit error rates with relatively simple device complexity.
Data Source
AI summary
The apparatus receives a first PDU and a first CRC that is based on the first PDU. The first PDU is encrypted based on a first nonce. The apparatus decrypts the first PDU to obtain a first payload and a first cipher stream. The apparatus soft combines the decrypted first payload with a decrypted set of payloads. The set of payloads have been encrypted based on at least one nonce different than the first nonce. The apparatus generates a second CRC based on the soft combined decrypted payloads and based on the first cipher stream. The apparatus determines whether the generated second CRC for the soft combined decrypted payloads passes a CRC check against the first CRC.