1. Download cafeteria photo from CTF website.
2. Crop logo on the glass. (I did it by gimp)
5. Check EXIF data of all images by ExifTool:
6. in this line you see nickname of image creator:
Comment : Designed by: nooneonemore.For: http://suctf.com/cce1/d393.
7. Make md5sum by this command in GNU/Linux shell:
echo -n "nooneonemore" | md5sum