You can use pack and unpack to transform it into something unintelligible from an "average human" standpoint. With those tools, you could convert it to 0's and 1's if you wanted, or uuencoding, though most likely you would just pack it from text to 'binary' format, and unpack it later. For that matter, you could even ROT-13 it with tr/A-Za-z/N-ZA-Mn-za-m/;

But that's not the ultimate in security. More like, simple obscurity. Don't put credit card numbers and missile launch codes into the file.