Lantern Radio, a small community station on the edge of town, went off air at three in the morning after a night of strange transmissions: Morse where the ident should be, keypad tones on the request line, a test card that wouldn’t go away, and interference that sounded like a broken organ. You have what the station kept: off-air recordings, camera stills, a capture from the studio-to-transmitter link and the engineers’ notes. The image and audio evidence needs looking at, not just reading, and a few questions reward reading slowly. Three findings unlock the next step of the trail.
Audio, intermediate, 150 points. At 02:13 the carrier came back, but instead of the station ident the off-air monitor recorded a tone keyed on and off. Decode it. It sends a codeword and a number: submit flag{codeword_number} in lower case, like flag{example_1234}.
Crypto, intermediate, 200 points. Straight after the Morse, a flat voice read out a message, and the monitor’s transcription service took it down letter by letter. It’s not English as it stands. The codeword the Morse sent is the key. Read the message; the flag is in it.
Audio, intermediate, 200 points. At 01:52 the request line rang. The call logger recorded it: it rings, someone picks up, and then nobody speaks, there are only keypad tones. Work out what the caller keyed in. It carries the flag, and something you’ll need later.
Audio, advanced, 300 points. The numbers broadcast promised “more follows on the outro”. This is the outro music the playout system sent at 02:58, just before the transmitter went dark. It sounds normal. Find what it carries; the request-line caller gave you the key.
Visual, intermediate, 200 points. When the station went dark, the website’s player showed this test card. It looks like every test card. The file is bigger than a card like this should be, and the engineers say their notes were “kept with the card”. Find the notes; the flag is the verification code in them.
Visual, advanced, 250 points. The transmitter site’s webcam saved this still at 02:57, three minutes before the carrier dropped. Only a mast, a light and stars. Someone who had the camera’s upload password used it to leave a message for whoever came looking. Find it.
Visual, advanced, 250 points. The studio’s security camera kept this frame from 02:40, when Studio 2 should have been empty. It looks like a dark, empty room. Something was written on it, one shade from the background. Read it, and submit it in lower case.
Visual, advanced, 300 points. This poster for the Night Sessions show was swapped onto the station’s website the evening before. The designer swears the file isn’t hers: it’s a palette image now, and hers wasn’t. Find what the new version hides. Submit it in lower case.
Audio, advanced, 400 points. Between programmes the off-air monitor caught a few seconds of what sounds like a broken organ. It was transmitted on purpose. Look at it rather than listen; the flag is drawn in it. Submit it in lower case.
Network, advanced, 250 points. The studio switch mirrors the studio-to-transmitter link (STL) to a capture box, which kept this tcpdump -x listing of the control session that switched the transmitter off. The segments are out of order and some came twice. Rebuild what the studio side sent to the transmitter on port 5004. The flag is in it, along with something the next challenge needs.
Crypto, advanced, 350 points. The capture box also saved the STL’s data frames from the same minutes. The link “encrypts” them with a short repeating XOR key that nobody wrote down. You know how every frame begins. Recover the key, read the frames, and find the flag.
Reasoning traps, intermediate, 150 points. Read the evening engineer’s handover note carefully. How did the night engineer get from the studio to the transmitter hut, and what is the latest time she could leave the studio and still start her shift on time? Use only what the note says. Submit flag{walk_HHMM} or flag{drive_HHMM}, with a 24-hour time and no colon, like flag{drive_0915}.
Reasoning traps, intermediate, 150 points. When the studio lost its link, the backup automation played a reel of tape. From the automation log, at what time did the tape run out, and how many minutes of programme did it play? Submit flag{HHMM_MINUTES}, a 24-hour time without the colon and a whole number of minutes, like flag{0415_37}.
Reasoning traps, intermediate, 200 points. Read the outage report. For how many minutes did listeners hear nothing at all, and on what day of the week did the outage end? Submit flag{MINUTES_weekday}, the day in lower case, like flag{12_friday}.
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