Q:

Multiple password encrypt/protect a single file

This one is tough to Google. I'm trying to find a solution or API to encrypt/protect a file with multiple passwords. The passwords would be handed out to users separately.
I looked at DotNetZip and the usual Zip and Rar solutions (including PKWare) for a way to multi-password protect a file.
All suggestions are welcome! I wouldn't be posting this question if it was either impossible or uncommon. Thanks!

A:

You can use passphrase-based OpenPGP encryption. It lets you specify several independent passphrases and supports compression. OpenPGPBlackbox package of our SecureBlackbox product does this (among a number of other features) and it's available for .NET, Java and VCL. 

