I want to securely backup my 80G HD, but doing a complete backup takes forever and slows down my machine, so I want to backup just 1G per day. Details:

% First hurdle: on the first day, I want to backup the "first" 1G of the hard drive. Of course, there really is no "first" 1G on a hard drive.

% After 80 days, I'll have my whole HD backed up... assuming none of my files ever change, which of course they do. So the backup plan/program must also catch file creation/changes as they come along.

% The backups must be consistent, in that I can restore my system by restoring the backups sequentially. In other words, "dd if=/harddrive" probably won't work.

% The backups should encrypt file contents AND names, but I don't see this as a major hurdle.

% Once the backup has backed up everything (even changed files), it can re-backup the first 1G on my hard drive. Even though this backup is redundant, that's OK, because I always want to be backing up something (eg, if I'm backing up to optical media, the older media might start going corrupt).

Is there a magic backup plan/program that does this?

In reality, I want to do this for multiple machines with multiple drives each, but think that solving the above will solve the general case.