Sensor Logs

Flag: XploitXβ{s1l3nt_0rb1t_c4rr13s_th3_3ncrypt3d_3ch0_1n_th3_fr4m3}

Unzipping the archive gives a second zip with four logs. Three of them (auth.log, network.log, system.log) each have a flag-looking string, but they're all decoys.

The interesting file is sensor_07.log. It starts out as text, then turns into binary after a --LOG_PAYLOAD-- marker. The binary part is a simple container where each entry is a 3-letter tag, a 4-byte length, then the data. It holds a PNG, a WAV, and a short TXT entry with _c4rr13s_th3_3ncrypt3d.

The WAV is just noise with a 58 Hz hum, and I found nothing in it. The PNG is a plain star field, but the red-channel LSBs in its top four rows carry data. Reading every third pixel gives:

XploitXβ{s1l3nt_0rb1t|_3ch0_1n_th3_fr4m3}|FAKE=XploitXβ{l0g_1s_cl34n}

The part after FAKE= is another decoy. The | in the real flag is a gap, and the TXT entry fits it: "silent orbit carries the encrypted echo in the frame."

import numpy as np
from PIL import Image

im = np.array(Image.open("a.png").convert("RGB")).astype(int)
bits = (im[:4, ::3, 0] == 13).astype(int).flatten()
data = bytes(int("".join(map(str, bits[i:i+8])), 2) for i in range(0, len(bits) - 7, 8))
print(data.decode("utf-8", "ignore"))

The | gap and the TXT entry filling it is my reading, so I haven't confirmed it against the checker. If it's rejected, try XploitXβ{s1l3nt_0rb1t_3ch0_1n_th3_fr4m3}.