Printf() to get the string representation of the So you need to use the "%u" formatter of sprintf() or On 64bit installationsĪll crc32() results will be positive integers though. Result in negative integers on 32bit platforms. No errors detected in compressed data of Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functions Classes and Objects Namespaces Enumerations Errors Exceptions Fibers Generators Attributes References Explained Predefined Variables Predefined Exceptions Predefined Interfaces and Classes Context options and parameters Supported Protocols and Wrappers Security Introduction General considerations Installed as CGI binary Installed as an Apache module Session Security Filesystem Security Database Security Error Reporting User Submitted Data Hiding PHP Keeping Current Features HTTP authentication with PHP Cookies Sessions Dealing with XForms Handling file uploads Using remote files Connection handling Persistent Database Connections Command line usage Garbage Collection DTrace Dynamic Tracing Function Reference Affecting PHP's Behaviour Audio Formats Manipulation Authentication Services Command Line Specific Extensions Compression and Archive Extensions Cryptography Extensions Database Extensions Date and Time Related Extensions File System Related Extensions Human Language and Character Encoding Support Image Processing and Generation Mail Related Extensions Mathematical Extensions Non-Text MIME Output Process Control Extensions Other Basic Extensions Other Services Search Engine Extensions Server Specific Extensions Session Extensions Text Processing Variable and Type Related Extensions Web Services Windows Only Extensions XML Manipulation GUI Extensions Keyboard Shortcuts ? This help j Next menu item k Previous menu item g p Previous man page g n Next man page G Scroll to bottom g g Scroll to top g h Goto homepage g s Goto searchīecause PHP's integer type is signed many crc32 checksums will When I extract that member to stdout & pipe though hexdump, we find it contains the two bytes string "ss" (hex 73 73) $ unzip -p tmp.zip | hexdump -Cįinally, as already mentioned in another comment, you can check that the CRC value is correct by running unzip -t $ unzip -t tmp.zip Length Method Size Cmpr Date Time CRC-32 Name It contains a single member 123.dat $ unzip -lv tmp.zip To work that out, I converted your hex dump back into a zip file, tmp.zip.
In your case the payload is the two byte sequence "ss". The CRC32 value in a zip is calculated by running the CRC32 algorithm against the complete uncompressed payload. Those bytes are the first few bytes of the zip file.
The byte sequence you are running against the online CRC calculator are not uncompressed bytes.
What am I doing wrong? The CRC-32 of the ZIP is the calculation of all the bytes (0-13) before, no? I went to this CRC-32 online calculator and added the following un-compressed row from the file: 50 4B 03 04 14 00 00 00 00 00 38 81 1C 51 I read that in a ZIP file the CRC-32 data is in bytes 14 to 17: Offset Bytes DescriptionĠ 4 Local file header signature = 0x04034b50 (read as a little-endian number) I want to validate that my ZIP file has a correct CRC-32 checksum.
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