Вокруг шум (Noise Around)

bug-makers

Task: a noise PNG with LSB-hidden song lyrics and flag; organizers also provided the original clean image. Solution: diff the two images to find ±1 LSB changes confined to the Red channel on a 18-px column grid, then use autocorrelation to discover a 7-cell stride and decode every 7th grid LSB as big-endian UTF-8.