Init. import

GAME/nas/Stegano/stego_task_solve.py

@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+import wave
+import struct
+import zlib
+import numpy as np
+
+SR = 44100
+SKIP_SEC = 1.0
+STEP = 2
+IN_WAV = "some_secret.wav"
+
+def read_wav_int16(path: str):
+    with wave.open(path, "rb") as wf:
+        assert wf.getnchannels() == 2
+        assert wf.getsampwidth() == 2
+        sr = wf.getframerate()
+        frames = wf.readframes(wf.getnframes())
+    arr = np.frombuffer(frames, dtype=np.int16).reshape(-1, 2)
+    return sr, arr
+
+def bits_to_bytes_big_endian(bits: np.ndarray) -> bytes:
+    # Длина должна быть кратна 8
+    n = (bits.size + 7) // 8 * 8
+    if n != bits.size:
+        bits = np.pad(bits, (0, n - bits.size), constant_values=0)
+    by = np.packbits(bits.astype(np.uint8), bitorder='big').tobytes()
+    return by
+
+def extract_header_and_length(right: np.ndarray, sr: int):
+    skip = int(sr * SKIP_SEC)
+    # Считываем первые 12 байт (заголовок: 4 + 4 + 4)
+    header_bits_count = 12 * 8
+    idxs = skip + np.arange(header_bits_count) * STEP
+    bits = (right[idxs] & 1).astype(np.uint8)
+    header = bits_to_bytes_big_endian(bits)
+    magic = header[:4]
+    if magic != b"STAG":
+        raise ValueError("Магия заголовка не совпала — это не тот контейнер.")
+    length = struct.unpack(">I", header[4:8])[0]
+    crc = struct.unpack(">I", header[8:12])[0]
+    return length, crc
+
+def extract_all(sr: int, stereo: np.ndarray):
+    right = stereo[:, 1]
+    length, crc_expected = extract_header_and_length(right, sr)
+    total_bytes = 12 + length
+    total_bits = total_bytes * 8
+    skip = int(sr * SKIP_SEC)
+    idxs = skip + np.arange(total_bits) * STEP
+    bits = (right[idxs] & 1).astype(np.uint8)
+    data = bits_to_bytes_big_endian(bits)
+    header = data[:12]
+    payload = data[12:12+length]
+    crc_actual = zlib.crc32(payload) & 0xFFFFFFFF
+    if crc_actual != crc_expected:
+        raise ValueError("CRC не сошлась — данные повреждены или неверные параметры извлечения.")
+    flag = zlib.decompress(payload).decode("utf-8")
+    return flag
+
+def main():
+    sr, stereo = read_wav_int16(IN_WAV)
+    flag = extract_all(sr, stereo)
+    print("[+] DATA [ ", flag, " ]")
+
+if __name__ == "__main__":
+    main()