How do I prevent OS X from modifying a text file?

How do I prevent OS X from modifying a text file?

I emailed a text file with \n line terminations to a friend who uses OS X.
In the process, the \n's turned into \r\n's. I presume that OS X did the
nasty deed. Is there anything I can put into the file to fool OS X into
not fiddling with my file?
(I need the file intact because the first line is an MD5 signature to
verify the rest of the file. The file is destined for an embedded system
via a flash stick)
I'll propose solution number 1: Create the file with \r\n to begin with.