How to encrypt a .zip file?

Question

Is it possible to encrypt a Zip file? I know encryption is used to make .txt files unreadable until decrypted with a key. Although I want to do the same with a .zip file.
I have multiple files I want users to download from the internet through my program I'm creating, so I thought I'll compress them files in a .zip and then encrypt the Zip for added security. (I don't want users to access the file within the .zip without a serial code)
I was going to keep the 'serial key' in a database online which the program would get.

Am going about this in the wrong way?

Answer 1

DotNetZip和SharpZipLib都支持加密拉链内容并且是免费的。

Answer 2

Use the dotnetzip library to perform your zipping/unzipping operations.

It supports AES encryption. From the website:

The library supports zip passwords, Unicode, ZIP64, stream input and output, AES encryption, multiple compression levels, self-extracting archives, spanned archives, and more.

Answer 3

Yes you can use third party zip libraries as shown by other answers, but keep in mind that your method of protecting files is rudimentary... it would not be terribly difficult to observe your program operating and recover the files after your program helpfully decrypts them. If you are storing the key as a constant in the program, that is pretty trivial to extract as well.

Software protection is a complex field, and it's very difficult to prevent determined users from viewing data that is stored on systems they control. Commercial software goes to great lengths to prevent this, and the solutions are quite complicated. (eg try hooking a debugger to Skype and see what happens)