The first file contained the start of the PNG, while the last file ( part2_375.7z ) contained the .
: Opening the first archive ( part2_0.7z ) in a hex editor revealed a PNG header ( 89 50 4E 47 ) and an IHDR chunk buried within the file structure itself, rather than in the extracted contents. The Pattern :
The PNG file was striped and hidden in the trailing bytes of the 7z archives, just before the footer. Parade_Buster-Final.7z
: Standard extraction and concatenation of the junk files failed to yield a valid binary.
The offset for the hidden PNG data could be calculated by comparing the reported "Packed Size" from the 7z -slt l command with the actual file structure. The first file contained the start of the
Concatenating these extracted bytes from all files produced a final, valid image file named , which contained the flag for the challenge. CTFtime.org / TastelessCTF 2020 / 7/12 / Writeup
The challenge provided a set of 376 individual 7zip archives (e.g., part2_0.7z through part2_375.7z ). Inside these archives were multiple "junk" files (e.g., junk_0.bin ), which initially appeared to be the primary data for extraction. Analysis & Solution : Standard extraction and concatenation of the junk
: To solve this, a script was used to loop through all 376 files, extract a specific block of bytes (typically 0x11 bytes) from each, and concatenate them. Final Result
