Binary Digits — Binary-Encoded JPEG Image

Challenge Overview

A file containing a long string of 1s and 0s — 71,192 characters total. The length is a multiple of 8, suggesting each group of 8 bits represents one byte of encoded data.

Analysis and Extraction

Converting each 8-bit group to its corresponding byte value and writing the result to a file:

with open("digits.bin", "r") as f:
    data = f.read().strip()

byte_array = bytearray()
for i in range(0, len(data) - len(data) % 8, 8):
    byte_array.append(int(data[i:i+8], 2))

with open("decoded.jpg", "wb") as f:
    f.write(byte_array)

File Type Identification

The first decoded bytes were FF D8 FF E0 followed by JFIF — the JPEG magic header. Running file decoded.jpg confirmed a valid JPEG image. Opening it revealed a white image with the flag printed in red text.

Magic Headers Reference