CS35L27-Covert-Channel-Analysis/report/technical-details.md

Technical Details

Extended Command Activity Breakdown

Command 0x81:

• Total occurrences: 1,432
• Near I2C address 0x40: High correlation
• Example contexts show byte 0x40 nearby
• Frequency: Very high (possibly every few seconds during use)

Command 0xC7:

• Total occurrences: 968
• Near I2C address 0x40: High correlation
• Example contexts show byte 0x40 nearby
• Frequency: High (possibly system event triggered)

Usage Pattern:

• Both commands appear throughout traces
• Not concentrated in boot or specific time
• Suggests ongoing use during operation

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GPIO Activity Breakdown

Bit 0x38 (209 operations):

• SETB: ~70 times
• CLR: ~139 times
• Pattern: More CLR than SETB (2:1 ratio)
• Interpretation: Possibly "active-low" control signal
• Frequency: Very high

Bit 0x34 (35 operations):

• Mix of SETB/CLR
• Frequency: Moderate
• Could be: Secondary control or status

Bit 0x3A (23 operations):

• Correlates: GPIO2 interrupt (from IODeviceTree)
• Frequency: Lower than others
• Likely: Interrupt signaling (expected)

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I2S Pattern Analysis

"I2SBHkZStack" String:

• Appears in audio subsystem traces
• "Stack" suggests software layer
• "BH" meaning unknown
• Could be: "Bidirectional Host" or "Base Host"

Value 0x03 Near I2S:

• 18 occurrences of pattern
• Cannot confirm: If this is mode register write
• Cannot confirm: Timing or context
• Need: Protocol analyzer or kernel trace