Add junk bytes to and of file

[Basher52]

Is there a way to add a small piece of junk after a file that later can easily be removed?
I use google as my backup server and before I email myself I split it up, but I want to 'cat' some kind of "junk" after each file so they cant easily just cat them together again and the the "true" file in there.

[Void Main]

Can you be a little more specific? Maybe provide an example? Not exactly sure what you mean by "junk".

[Basher52]

well...
I split up the big backup files into smaller and send them to the backup server, but I want to add some kind of junk and by that I mean whatever, just so if anyone but me tries to 'cat' the files together again, it won't get a working RAR file.
The junk can be anything at all just so the 'cat' of these files won't create a working RAR file making it harder to decrypt it.

[Void Main]

dd should work just fine for that.

[Basher52]

yeah you're right. thx for reminding me