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Sand Castles on the Beach
Challenge
We found this very mysterious image, it doesn’t look complete and there seems to be something hidden on it… does this mean anything to you? sandcastle.png. This flag is not in the standard flag format, add IceCTF{} to the message when you’ve found it. The flag is all lowercase, and contains no special characters.
Solution
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$ exiftool sandcastle.png [15-08-16 14:04:42]
ExifTool Version Number : 10.10
File Name : sandcastle.png
Directory : .
File Size : 381 kB
File Modification Date/Time : 2016:08:12 22:24:08+02:00
File Access Date/Time : 2016:08:12 22:24:08+02:00
File Inode Change Date/Time : 2016:08:12 22:24:08+02:00
File Permissions : rwxrwxrwx
File Type : PNG
File Type Extension : png
MIME Type : image/png
Image Width : 616
Image Height : 428
Bit Depth : 8
Color Type : RGB
Compression : Deflate/Inflate
Filter : Adaptive
Interlace : Noninterlaced
Pixels Per Unit X : 3780
Pixels Per Unit Y : 3780
Pixel Units : meters
Modify Date : 2016:06:19 11:14:52
Comment : 58-7-9.210-13-2.67-3-16.85-17-15.305-18-4.83-12-18.75-8-15.47-4-2.83-20-11.208-6-6.85-11-6.75-7-3.106-9-14
Image Size : 616x428
Megapixels : 0.264
the comment in the exifdata looks like it could be a book cipher, we identified the image to be part of the cover to the fourth edition of Cryptography and Network Security by William Stallings.
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58-7-9.210-13-2.67-3-16.85-17-15.305-18-4.83-12-18.75-8-15.47-4-2.83-20-11.208-6-6.85-11-6.75-7-3.106-9-14
page-line-character?
page-line-word (and then first letter of word)?
58-7-9
210-13-2
67-3-16
85-17-15
305-18-4
83-12-18
75-8-15
47-4-2
83-20-11
208-6-6
85-11-6
75-7-3
106-9-14
Flag