ruby,file-io,binary , XOR binary file in Ruby

Question:

Tag: ruby,file-io,binary

I'm trying to create a "xor" function in Ruby that takes in input a binary file and an hex value and generates a xored binary file in output.

File.open("myfile.exe.xor",'w') do |f_xor|
f_xor.puts File.open("myfile.exe", 'rb').to_i ^ 0xFF
end


This code seems not to return the correct xored file as the expected MD5 is different. I've been using a XOR command line tool for Linux so far but I want to switch to an OS-agnostic version to also deploy the code on Windows.

Could you help me understand what's wrong?

Calling to_i on a file handle returns the low-level identifier for it, a singular number, nothing more.

If you want to operate on the bytes themselves:

File.open(input_file, 'rb') do |f|
File.open(output_file, 'wb') do |o|
o.write(
byte ^ xor_value
end.pack("C*")
)
end
end


The key here is to apply the XOR operation on each of the bytes in the file, then write out that result. Using puts is a mistake since it appends a linefeed.

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