C32zip -

: The "Extra Field" length and content are often manipulated to hide data or throw off automated parsers.

To solve these "C32" related zip challenges, one must understand the ZIP file format : : Starts with the signature 50 4B 03 04 . C32zip

: Once lengths and CRC values are consistent, standard tools like 7z or unzip will be able to process the file correctly. CTFtime.org / PlaidCTF 2017 / zipper / Writeup : The "Extra Field" length and content are

In this specific challenge, players are given a ZIP file ( zipp.zip ) that appears broken. Upon inspection with a hex editor, several issues are discovered that prevent standard extraction: CTFtime

: Use binwalk or file to confirm it is a ZIP. Try to unzip it; if it fails with "filename too long" or "offset error," the headers are tampered with.

: The filename length field in the local file header is set to an impossibly large value (e.g., 9001 or 0x2329 ), causing extraction tools to fail or truncate the filename.

: Offset 0x1A . This is the value often tampered with in CTF challenges like "zipper". Solving Steps (Long Write-up Style)