The Windows and Mac ports of GPG usually only include the basic options, but the standard command line GPG for Linux has the --throw-keyid option which enters zeros for the key id. In that case, your PGP client will try every private key that you own until it is able to decrypt the message or fails. Anyone to whom the message is not encrypted won't know who the recipients are, even if they have their public keys. In that way, you could encrypt the message to multiple recipients and they won't know who the others are, although they would know how many recipients there are. Edit: I should point out that I'm talking about the GUIs. When you extract GPG4USB, you will get gpg.exe in a subfolder called bin. It is a direct port of the Linux command line client with all of the options, so this will work gpg.exe --throw-keyid --armor -r Recipient1 -r Recipient2 -e address.txt Encrypted and anonymous.