Clear it in 3 steps
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Start the environment
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Investigate the target
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Submit the flag
All challenges
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Network Analysis - Custom Protocol Decoding
Mission
Traffic from a system using a small custom binary protocol was captured. Download the packet capture (traffic.pcap), analyze the frame structure on TCP port 9999, and decode the payload to recover the flag.
Hints
Hint 1 Show
Each message is magic(2 bytes "KG") | length(1 byte) | body(length bytes)
Hint 2 Show
The body is XORed with a fixed one-byte key; infer it from the client HELLO message
Hint 3 Show
The key is 0x42; XOR the server response frame body with 0x42 to get the flag