Create an encrypted disk image: it mounts like a disk, and is password-protected. Put your files in there and make as many copies as you want; give them to whomever.
The disk image can be a single file, or a bundle (Sparse Bundle Disk Image). Like app bundles, Finder will show them as a single thing, but in reality it's a directory with multiple files (called "bands"). Because it's sparse, it grows as you put stuff in it. Because it's a bundle, it can be backed up more efficiently. With a single monolithic file, changing a single bit "on the disk" modifies that file and the whole thing has to be backed up again. With a bundle, only the bands that change have to be copied. Also, a bundle may be stored on a disk formatted with FAT32, because the bands are much smaller than the single-file size limit; yet it can still store a dozen-GB file.
On the external drive, create one disk image or many, organized however you want. The size of the images should allow for future expansion; you can move the images to larger and larger external drives over time. Make backups of your files. Unmount/eject the external drive, and the bundles it contains are unmounted at the same time.
Give the drive to the friend, who can then copy the .sparsebundle
"files". If they're savvy, they can do an rsync
on subsequent backups to minimize the copying. Note that if they put their copy onto a disk that is backed up by Time Machine, the bundle will also be backed up efficiently.
for Windows you could use a password-protected
.zip
archive -- I don't know of anything like that for Mac though – Nate Koppenhaver – 2011-11-03T03:40:24.880