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Goals

ASCII values

0-31 are invalid
32-255 = 224 valid chars

Requirements

  • read from a preset text file
  • provide the option to encrypt or decrypt
    • if encrypt, request a password and generate the encryption key
    • ord() characters and use encryption key to shift letters
    • save to a new file
    • if decrypt, request a password and generate the encryption key
    • use encryption key to shift letters and chr() characters
    • save to a new file

Additional Goals

  • Use a GUI (probably Tkinter) to select the input and output file (NOTE: tkFileDialog requires Tkinter, but is not part of the module)
  • Use another form of encryption OR add onto the shift encryption (use Checkcryption as inspiration)
  • NOTE: non-ASCII chars throw a TypeError in ord(), and a ValueError in chr()

Encryption Method

Key Generation

  • One to one, password to key
  • Require the password to be all ASCII, min 3 chars
  • Split into sets of 3
    • ord() and the 1st/2nd/3rd char in each set has its own numeric equivalent, append to in-progress key
  • Divide the sum of the digits by the number of digits (val1), then find the remainder of that number divided by 10 (val2)
  • Add val2 after the floor division halfway point of the in-progress key

Text Encoding

  • ord() every character into a list
  • Modulo divide key[-3:] by 224 and right shift by that number, looping as necessary
  • Add 3*key[0] to every key[3]^th space in the original, looping as necessary
  • Add digits of key repeatedly until the number is single digit, and then insert random.randint(0,223)+32 to every ^th position (this may not run, that's ok)
  • chr() back to a string and save

Text Decoding

  • ord() every character into a list
  • Add digits of key repeatedly until the number is single digit, then run something similar to the following code (tested and verified):
a=[1,1,2,1,1,2,1,1,2,1]

for i in range(n): # n = number of times it can possible occur (division math req.)
    del a[2*(i+1)] # 2 = the single digit number from the key
  • Subtract 3*key[0] from every key[1]^th space in the original, reverse looping as necessary
  • Modulo divide key[-3:] by 224 and left shift by that number, looping as necessary
  • chr() back to a string and save

https://pythonprogramming.net/object-oriented-programming-crash-course-tkinter/