I am looking to give some files to my accountant, who is not computer-savvy. I am going to put the files on a flash drive encrypted. I assume, accountant has no software other than standard Windows for decryption. I cannot rely on accountant being smart enough to download and install tools like truecrypt or 7-zip. I am also assuming accountant will be reluctant to run self-extracting executable, or at least I hope he is not that careless.
At this time, the best that option that comes to my mind will be to pack the files into a password protected zip file. This will, however divulge the file names, which I also want to hide, so I will have to zip the files twice - once into an non-encrypted archive, and second time into a secure one. I think there is a header encryption in newest zip format, but I could not find free tools that would do it (7-zip doesn't). Also I don't know if Windows is capable of decrypting such archive.
Can anybody think of a better option?