XOR Defender

Write a command line ruby application that can either encrypt or decrypt a text file, given a key.

Important Files:

• xor_defend.rb: a command line application that encodes/decodes a file given a key and prints the results to STDOUT
  • uses xor_helper.rb for encoding/decoding logic
  • do NOT make any edits to this file
• xor_helper.rb: this contains the actual logic for encoding/decoding
  • you need to add code in this file to make everything work
• test.txt: a sample test file for input (you may try your own)

Requirements (follow carefully)

• Download the following files: xor_defend.rb, xor_helper.rb, test.txt (you can click on them and download the 'RAW' version)
• [30 pts] Implement the encode method in xor_helper.rb
  • Do not add any code outside this method
  • [10 pts] Note that the key may have several characters. Rotate through the characters of your key as you encode each character of the text document.
• [10 pts] Coding style
  • Do not use any for/while/until loops; use only map/reduce/each on enumerable types (Array, Hash)
  • Aim for readability of code over cleverness
  • Test your code against the test.txt file

Testing

To check if your solution works, you can try to encode the test.txt file to another output file, and then encode that one more time to see if you get the same contents as `test.txt.

You should be able to test it as follows from the command line:

• See the contents of the test file

  $ cat test.txt

• Encode the test file and redirect output to another file

  $ ruby xor_defend.rb test.txt mykey > out.txt

• See contents of output file

  $ cat out.txt

• Re-encode output file to see if screen output matches orignal test file

  $ ruby xor_defend.rb out.txt mykey

If everything works, you may submit your solution

Submit Solution

• Each person on your team should do this homework (you may work together) and upload a gist, but only need to submit one solution for grading per team.
• Upload your team's final xor_helper.rb file to gist.github.com
• Submit the URL of your gist (xor_helper.rb) to Canvas