How to "disguise" (encrypt?) a (zip) file?

[kb]

Hi, I have written a file packer for a game engine. The packer uses Zip compression (based on the zlib library), and so any packed files can easily be opened with WinZip, EnZip etc. However, I would like to give them better protection. Currently they can be password protected (and the password is encrypted), so people can open the zip file but not extract any of the contents. However, I was wondering if there was any way to make the Zip file unreadable to WinZip etc and only readable to my program. Any suggestions would be much appreciated. Many thanks, KB

[Tomasz Sowinski]

Create an unprotected .zip with dummy name containing all files and zip it again with a password. Users will be able to see one filename in protected .zip. Tomasz Sowinski -- http://www.shooltz.com

** Putt knot yore thrust inn spel chequers. **

[Jon Hulatt]

or, mangle the data as you write it to the file. very simple way would be to pick a random DWORD, and xor every 4 bytes with it. This should screw the thing up enough that winzip won't make head or tail of it. Then, as you read it, xor again with the same number to get back to where you started. STL is a religeon. Enquiries to Reverend Christian Graus

[kb]

Thanks both for your replies - I think I may well try to change the way it writes, as Jon Hulatt suggests. This will obviously mean writing my own packer utility too (I was using WinZip to pack and then my own program only needed to unpack), but that shouldn't be too bad. Thanks again, KB

[Jon Hulatt]

no need. pack with winzip, just write a quick program that opens your zip file and writes a new mangled one. STL is a religeon. Enquiries to Reverend Christian Graus

[Mike Nordell]

I added exactly this capability to zziplib some time ago.