Mercurial > public > m209
changeset 16:1448d698f9e4
Refactor the encrypt procedure into a class.
| author | Brian Neal <bgneal@gmail.com> |
|---|---|
| date | Sat, 08 Jun 2013 12:55:07 -0500 |
| parents | 2e2692fb7de6 |
| children | c8027f88443f |
| files | m209/procedure.py m209/tests/test_procedure.py |
| diffstat | 2 files changed, 101 insertions(+), 93 deletions(-) [+] |
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--- a/m209/procedure.py Fri Jun 07 22:30:33 2013 -0500 +++ b/m209/procedure.py Sat Jun 08 12:55:07 2013 -0500 @@ -21,7 +21,7 @@ import random from . import M209Error -from .converter import M209_ALPHABET_SET, M209_ALPHABET_LIST +from .converter import M209, M209_ALPHABET_SET, M209_ALPHABET_LIST from .key_wheel import KeyWheelError @@ -29,108 +29,120 @@ pass -def encrypt(m_209, plaintext, group=True, spaces=True, key_list=None, - key_list_ind=None, ext_msg_ind=None, sys_ind=None): - """Encrypts a plaintext message using standard procedure. The encrypted text - with the required message indicators are returned as one string. +class StdEncryptProcedure: + """This class encapsulates the "standard" encrypt procedure for the M-209 as + found in the training film T.F. 11 - 1400. - The encrypt function accepts these parameters: - - m_209 - A M209 converter instance - plaintext - Input string of text to be encrypted - group - If True, the resulting encrypted text will be grouped into 5-letter - groups with a space between each group. If False, no spaces will be - present in the output. - spaces - If True, space characters in the input plaintext will automatically - be replaced with 'Z' characters before encrypting. - key_list - If not None, this must be a KeyList instance and it will be - used to setup the m_209 machine. If None, it is assumed the M209 is - already setup in the desired configuration. - key_list_ind - If key_list is None, then this parameter must be supplied, - and it is the key list indicator that was used to setup the M209. - ext_msg_ind - This is the external message indicator, which, if supplied, - must be a valid 6 letter string of key wheel settings. If not supplied, - one will be generated randomly. - sys_ind - This is the system indicator, which must be a string of length - 1 in the range 'A'-'Z', inclusive. If None, one is chosen at random. - - It is an error to supply both key_list and key_list_ind options. Supply one - or the other. A ProcedureError will be raised if both are supplied or if - neither are supplied. + The procedure can be configured with an optional M-209, and optional key + list to be used for the day. If the M-209 is not supplied, one will be + created internally. Before an encrypt() operation can be performed, a key + list must be supplied. This can be done at construction time or via the + set_key_list() method. """ - # Ensure we have a key list indicator and there is no ambiguity: + def __init__(self, m_209=None, key_list=None): + self.m_209 = m_209 if m_209 else M209() - if (key_list and key_list_ind) or (not key_list and not key_list_ind): - raise ProcedureError("encrypt requires either key_list or key_list_ind but not both") + if key_list: + self.set_key_list(key_list) - # Setup M209 machine if necessary + def set_key_list(self, key_list): + """Use the supplied key list for all future encrypt operations. - if key_list: - m_209.set_drum_lugs(key_list.lugs) - m_209.set_all_pins(key_list.pin_list) - key_list_ind = key_list.indicator + Configure the M209 with the key list parameters. - if len(key_list_ind) != 2: - raise ProcedureError("key list indicator must be two letters") + """ + if len(key_list.indicator) != 2: + raise ProcedureError("invalid key list indicator") - m_209.letter_counter = 0 + self.key_list = key_list + self.m_209.set_drum_lugs(key_list.lugs) + self.m_209.set_all_pins(key_list.pin_list) - # Set key wheels to external message indicator - if ext_msg_ind: - try: - m_209.set_key_wheels(ext_msg_ind) - except M209Error as ex: - raise M209Error("invalid external message indicator {} - {}".format( - ext_msg_ind, ex)) - else: - ext_msg_ind = m_209.set_random_key_wheels() + def encrypt(self, plaintext, group=True, spaces=True, ext_msg_ind=None, sys_ind=None): + """Encrypts a plaintext message using standard procedure. The encrypted text + with the required message indicators are returned as one string. - # Ensure we have a valid system indicator - if sys_ind: - if sys_ind not in M209_ALPHABET_SET: - raise ProcedureError("invalid system indicator {}".format(sys_ind)) - else: - sys_ind = random.choice(M209_ALPHABET_LIST) + The encrypt function accepts these parameters: - # Generate internal message indicator + plaintext - Input string of text to be encrypted + group - If True, the resulting encrypted text will be grouped into 5-letter + groups with a space between each group. If False, no spaces will be + present in the output. + spaces - If True, space characters in the input plaintext will automatically + be replaced with 'Z' characters before encrypting. + ext_msg_ind - This is the external message indicator, which, if supplied, + must be a valid 6 letter string of key wheel settings. If not supplied, + one will be generated randomly. + sys_ind - This is the system indicator, which must be a string of length + 1 in the range 'A'-'Z', inclusive. If None, one is chosen at random. - int_msg_ind = m_209.encrypt(sys_ind * 12, group=False, spaces=False) + A ProcedureError will be raised if the procedure does not have a key + list to work with. - # Set wheels to internal message indicator from left to right. We must skip - # letters that aren't valid for a given key wheel. - it = iter(int_msg_ind) - n = 0 - while n != 6: - try: - m_209.set_key_wheel(n, next(it)) - except KeyWheelError: - pass - except StopIteration: - assert False, "Ran out of letters building internal message indicator" + """ + # Ensure we have a key list indicator and there is no ambiguity: + + if not self.key_list: + raise ProcedureError("encrypt requires a key list") + + self.m_209.letter_counter = 0 + + # Set key wheels to external message indicator + if ext_msg_ind: + try: + self.m_209.set_key_wheels(ext_msg_ind) + except M209Error as ex: + raise M209Error("invalid external message indicator {} - {}".format( + ext_msg_ind, ex)) else: - n += 1 + ext_msg_ind = self.m_209.set_random_key_wheels() - # Now encipher the message on the M209 - ciphertext = m_209.encrypt(plaintext, group=group, spaces=spaces) + # Ensure we have a valid system indicator + if sys_ind: + if sys_ind not in M209_ALPHABET_SET: + raise ProcedureError("invalid system indicator {}".format(sys_ind)) + else: + sys_ind = random.choice(M209_ALPHABET_LIST) - # If we are grouping, and the final group in the ciphertext has less than - # 5 letters, pad with X's to make a complete group: - if group: - total_len = len(ciphertext) - num_groups = total_len // 5 - num_spaces = num_groups - 1 if num_groups >= 2 else 0 - x_count = 5 - (total_len - num_spaces) % 5 - if 0 < x_count < 5: - ciphertext = ciphertext + 'X' * x_count + # Generate internal message indicator - # Add the message indicators to pad each end of the message + int_msg_ind = self.m_209.encrypt(sys_ind * 12, group=False) - pad1 = sys_ind * 2 + ext_msg_ind[:3] - pad2 = ext_msg_ind[3:] + key_list_ind + # Set wheels to internal message indicator from left to right. We must skip + # letters that aren't valid for a given key wheel. + it = iter(int_msg_ind) + n = 0 + while n != 6: + try: + self.m_209.set_key_wheel(n, next(it)) + except KeyWheelError: + pass + except StopIteration: + assert False, "Ran out of letters building internal message indicator" + else: + n += 1 - msg_parts = [pad1, pad2, ciphertext, pad1, pad2] + # Now encipher the message on the M209 + ciphertext = self.m_209.encrypt(plaintext, group=group, spaces=spaces) - # Assemble the final message; group if requested - sep = ' ' if group else '' - return sep.join(msg_parts) + # If we are grouping, and the final group in the ciphertext has less than + # 5 letters, pad with X's to make a complete group: + if group: + total_len = len(ciphertext) + num_groups = total_len // 5 + num_spaces = num_groups - 1 if num_groups >= 2 else 0 + x_count = 5 - (total_len - num_spaces) % 5 + if 0 < x_count < 5: + ciphertext = ciphertext + 'X' * x_count + + # Add the message indicators to pad each end of the message + + pad1 = sys_ind * 2 + ext_msg_ind[:3] + pad2 = ext_msg_ind[3:] + self.key_list.indicator + + msg_parts = [pad1, pad2, ciphertext, pad1, pad2] + + # Assemble the final message; group if requested + sep = ' ' if group else '' + return sep.join(msg_parts)
--- a/m209/tests/test_procedure.py Fri Jun 07 22:30:33 2013 -0500 +++ b/m209/tests/test_procedure.py Sat Jun 08 12:55:07 2013 -0500 @@ -7,8 +7,7 @@ import unittest from ..keylist import KeyList -from ..procedure import encrypt -from ..converter import M209 +from ..procedure import StdEncryptProcedure PLAINTEXT = 'ATTACK AT DAWN' @@ -29,11 +28,8 @@ 'ACDFHIMN' ], letter_check = 'TNMYS CRMKK UHLKW LDQHM RQOLW R') - self.m_209 = M209() + self.proc = StdEncryptProcedure(key_list=self.fm) def test_encrypt(self): - - result = encrypt(self.m_209, PLAINTEXT, key_list=self.fm, - ext_msg_ind='ABCDEF', sys_ind='G') - + result = self.proc.encrypt(PLAINTEXT, ext_msg_ind='ABCDEF', sys_ind='G') self.assertEqual(result, CIPHERTEXT)