finished command line arguments for decryption

Author: D10f

route-cipher.py

@@ -0,0 +1,182 @@
+#!/usr/bin/env python3
+
+"""
+reoute-cipher.py
+"""
+
+from pathlib import Path
+from copy import deepcopy
+from argparse import ArgumentParser
+import logging
+import sys
+
+# TEST_CIPHERTEXT = '16 12 8 4 0 1 5 9 13 17 18 14 10 6 2 3 7 11 15 19'
+# TEST_COLS = 4
+# TEST_ROWS = 5
+# TEST_KEY = '-1 2 -3 4' # negative reads upwards, positive downwards
+
+logger = None
+
+def main():
+  args = parse_arguments()
+  logger = init_logger(args.verbose)
+  
+  if args.file:
+    logger.info(f'Reading from file at {args.file.resolve()}')
+    with open(args.file) as f:
+      ciphertext = f.read()
+  else:
+    ciphertext = args.message
+
+  validate_length(ciphertext, args.rows, args.columns)
+
+  translation_matrix = create_matrix(
+    ciphertext,
+    args.key,
+    args.columns,
+    args.rows
+  )
+
+  print(logger.getEffectiveLevel())
+
+  if logger.getEffectiveLevel() >= 10:
+    print_matrix(translation_matrix)
+
+  plaintext = decrypt(translation_matrix, args.rows)
+
+  print(plaintext)
+
+
+def validate_length(ciphertext, rows, cols):
+  """
+  Checks that the input columns and rows are valid respective to the
+  ciphertext length.
+  """
+  factors = []
+  len_cipher = len(ciphertext.split())
+
+  # Exclude 1x1 grids as that would be ciphertext
+  for i in range(2, len_cipher):
+    if len_cipher % i == 0:
+      factors.append(i)
+  
+  if rows * cols != len_cipher:
+    print("Error - Input columns and rows not factors of length of ciphertext.")
+    sys.exit(1)
+
+
+def validate_key(key, cols):
+  """Turn key into list of integers and checks it for validity"""
+
+  key_int = [int(k) for k in key.split()]
+  lowest = min(key_int)
+  highest = max(key_int)
+
+  if 0 in key_int:
+    print('Invalid key - 0 is not a valid value')
+    sys.exit(1)
+
+  if (
+    len(key_int) != cols or \
+    lowest < -cols or \
+    highest > cols
+  ):
+    print('Invalid key - Invalid number of of columns and/or rows')
+
+  return key_int
+
+
+def decrypt(matrix, rows):
+  plaintext = ''
+  matrix_copy = deepcopy(matrix)
+  
+  for _ in range(rows):
+    for col in matrix_copy:
+      word = str(col.pop())
+      plaintext += word + ' '
+
+  return plaintext
+
+
+def create_matrix(ciphertext, key, cols, rows):
+  """Turns a given ciphertext into a matrix of size cols x rows"""
+
+  ciphertext_list = ciphertext.split()
+  translation_matrix = [None] * cols
+  start = 0
+  stop  = rows
+
+  for k in validate_key(key, cols):
+
+    col_items = ciphertext_list[start:stop]
+
+    # Reverse order of ciphertext based on sign on key
+    if int(k) > 0:
+      col_items = list(reversed(col_items))
+
+    # Subtract one for python's 0 index
+    translation_matrix[abs(int(k)) - 1] = col_items
+    
+    # Increase counters for next iteration
+    start += rows
+    stop += rows
+
+  return translation_matrix
+
+
+def print_matrix(matrix):
+  print('Translation Matrix', *matrix, sep='\n')
+
+
+def init_logger(verbosity):
+  logger = logging.getLogger(__name__)
+  if verbosity == 1:
+    logger.setLevel(logging.INFO)
+  if verbosity > 1:
+    logger.setLevel(logging.DEBUG)
+  return logger
+
+
+def parse_arguments():
+  parser = ArgumentParser()
+
+  parser.add_argument('-k', '--key',
+    help='key used to encrypt/decrypt the message'
+  )
+  parser.add_argument('-c', '--columns',
+    help='Number of "columns" to use to create the route cipher',
+    type=int
+  )
+  parser.add_argument('-r', '--rows',
+    help='Number of "rows" to use to create the route cipher',
+    type=int
+  )
+
+  operations = parser.add_mutually_exclusive_group(required=True)
+  operations.add_argument('-e', '--encrypt',
+    help='run script with encryption instructions',
+    action='store_true'
+  )
+  operations.add_argument('-d', '--decrypt',
+    help='run script with decryption instructions',
+    action='store_true'
+  )
+
+  source = parser.add_mutually_exclusive_group(required=True)
+  source.add_argument('-m', '--message',
+    help='string to either encrypt or decrypt'
+  )
+  source.add_argument('-f', '--file',
+    help='path to file containing the ciphertext',
+    type=Path
+  )
+
+  parser.add_argument('-v', '--verbose',
+    help='prints additional information to terminal output',
+    action='count'
+  )
+  return parser.parse_args()
+
+
+if __name__ == '__main__':
+  main()