: Located at offset 0x0E . This is the checksum of the uncompressed data. Compressed Size (4 bytes) : Offset 0x12 . Uncompressed Size (4 bytes) : Offset 0x16 .
: 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 C32zip
: If the file is encrypted or the data is missing, check the uncompressed size . If the size is very small (e.g., 4-6 bytes), you can use a script to find which alphanumeric string produces the CRC32 hash found in the header. : Located at offset 0x0E
: 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. Uncompressed Size (4 bytes) : Offset 0x16
To solve these "C32" related zip challenges, one must understand the ZIP file format : : Starts with the signature 50 4B 03 04 .
: The "Extra Field" length and content are often manipulated to hide data or throw off automated parsers.