cryptopuzzle.py

"""
Symmetric encryption tool
"""
from base64 import b64encode
import sys

def main():
  usage = "Usage: {sys.argv[0]} [test | encrypt | decrypt | crack]"

  # If no argument, print the command usage
  if len(sys.argv) != 2:
    print(usage)
    return

  # Run the correct function based on the command
  cmd = sys.argv[1]
  if cmd == "test":
    runTests()
  elif cmd == "encrypt":
    runEncrypt()
  elif cmd == "decrypt":
    runDecrypt()
  elif cmd == "crack":
    runCrack()
  else:
    # Unknown command, just print usage
    print(usage)

def runTests():
  challenge1()
  challenge2()
  challenge3()
  challenge4()
  challenge5()

def runEncrypt():
  # TODO
  pass

def runDecrypt():
  # TODO
  pass

def runCrack():
  challenge8()
  challenge9()

def encrypt(msg, key):
  # TODO
  pass

def decrypt(ctxt, key):
  # TODO
  pass

def expandKey(key, size):
  # TODO
  pass

def xor(bytes1, bytes2):
  # TODO
  pass

def challenge1():
  print("Challenge 1")
  bytes1 = bytes.fromhex("7f3a4f1351f85b0344223e1177e14707190c0e311f4ca633f5f3e9352372")
  bytes2 = bytes.fromhex("07e32c180dfa56496a461627542115132a4c284050495b23e2245b093159")
  expectedResult = bytes.fromhex("78d9630b5c020d4a2e64283623c05214334026714f05fd1017d7b23c122b")
  result = xor(bytes1,bytes2)
  print("bytes1+bytes2=", result.hex())
  assert(result == expectedResult)
  print("Passed!\n")

def challenge2():
  print("Challenge 2")
  A = bytes.fromhex("e72d1d1f103807590f4339575e00381074485d2d580249f744052605e11d")
  B = bytes.fromhex("07e32c180dfa56496a461627542115132a4c284050495b23e2245b093159")
  C = xor(A,B)

  # TODO: Write some print and/ assert statements
  print("A+C=", None)
  print("B  =", None)
  # assert(False)

  print("C+B=", None)
  print("A  =", None)
  # assert(False)

  # print("Passed!\n")

def challenge3():
  print("Challenge 3")
  # Here we use a encode() to turn a string (not hex string) into
  # a sequence of bytes
  key = "FETCH".encode()
  longkey = expandKey(key, 18)
  print(f"longkey={longkey}")
  assert(longkey == "FETCHFETCHFETCHFET".encode())
  print("Passed!\n")

def challenge4():
  print("Challenge 4")
  key = "GRETCHEN".encode()
  message = "They say her hair is so big because it's full of secrets".encode()
  ciphertext = encrypt(message, key)
  expectedCiphertext = bytes.fromhex("133a202d633b2437673a20266320242735722c27633b2a6e253b2274212d262f322120742a3c623d673430382f682a2867212037312d313d")
  print(f"ciphertext={ciphertext.hex()}")
  assert(ciphertext == expectedCiphertext)
  print("Passed!\n")

def challenge5():
  print("Challenge 5")
  key = "GROOL".encode()
  message = "She doesn't even go here.".encode()

  ciphertext = encrypt(message, key)
  print(f"ciphertext={ciphertext.hex()}")

  recoveredMessage = decrypt(ciphertext, key)
  print(f"recoveredMessage={recoveredMessage}")

  assert(recoveredMessage == message)
  print("Passed!\n")

def challenge8():
  print("Challenge 8")
  ciphertext = bytes.fromhex("18763c713f3e25713071233436243d3023713c3e3c7d7118763c713071323e3e3d713c3e3c70")

  # TODO
  assert(False)
  print("\n")

def challenge9():
  print("Challenge 9")
  ciphertext = bytes.fromhex("022b611928212f2b3e2120376a3661392865362b2c37613e242b2a60")

  # TODO
  assert(False)

# Run!
if __name__ == '__main__':
  main()