0 weekly points · Practice mode
Ravi swiped into the last train of the night and never came out. All we recovered is his ticket stub, the platform PA recording from that train, and the gate controller's glossary file.
Rumour is the PA system was carrying more than announcements. The gate logged more than one passenger that night.
Objective
Find what Ravi was carrying.
#Investigation notes
Hint
The technician who inspected the PA line says the left and right speakers were wired out of phase that night. Whatever else was on the line only ever showed up in the difference between them.
The gate controller writes every log frame the same way: the first two bytes are always the ASCII letters NM. If your decoded bytes don't start with NM, something is off in how you turn the signal into bits.
Warning
Not every flag-shaped string in these files is real, and a wrong decryption can still produce something that looks like a flag. Only the passenger whose serial matches Ravi's stub is his.
#Files
| File | Description |
|---|---|
announcement.wav | Platform PA recording from the train |
ticket.png | Ravi's ticket stub |
gate_glossary.txt | The gate controller's glossary file |
Flag
The flag format is rvcectf{...}. Submit the entire string, braces included.
Files
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