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Fixed warning string for Key B = 0 (#1639)

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* Fixed warning string for Key B = 0

* Update affine_cipher.py

* Update affine_cipher.py

* decrypt_message(encrypt_message())

Co-authored-by: Christian Clauss <cclauss@me.com>
This commit is contained in:
Saransh Gupta 2019-12-21 04:22:43 +05:30 committed by Christian Clauss
parent c67776da59
commit 1d9266eca0
1 changed files with 48 additions and 41 deletions
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89
ciphers/affine_cipher.py
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@ -1,56 +1,63 @@
import sys, random, cryptomath_module as cryptoMath import random
import sys
SYMBOLS = r""" !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~""" import cryptomath_module as cryptomath
SYMBOLS = (r""" !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`"""
r"""abcdefghijklmnopqrstuvwxyz{|}~""")
def main(): def main():
message = input("Enter message: ") """
key = int(input("Enter key [2000 - 9000]: ")) >>> key = get_random_key()
mode = input("Encrypt/Decrypt [E/D]: ") >>> msg = "This is a test!"
>>> decrypt_message(key, encrypt_message(key, msg)) == msg
True
"""
message = input("Enter message: ").strip()
key = int(input("Enter key [2000 - 9000]: ").strip())
mode = input("Encrypt/Decrypt [E/D]: ").strip().lower()
if mode.lower().startswith("e"): if mode.startswith("e"):
mode = "encrypt" mode = "encrypt"
translated = encryptMessage(key, message) translated = encrypt_message(key, message)
elif mode.lower().startswith("d"): elif mode.startswith("d"):
mode = "decrypt" mode = "decrypt"
translated = decryptMessage(key, message) translated = decrypt_message(key, message)
print("\n%sed text: \n%s" % (mode.title(), translated)) print(f"\n{mode.title()}ed text: \n{translated}")
def getKeyParts(key): def check_keys(keyA, keyB, mode):
keyA = key // len(SYMBOLS) if mode == "encrypt":
keyB = key % len(SYMBOLS) if keyA == 1:
return (keyA, keyB) sys.exit(
"The affine cipher becomes weak when key "
"A is set to 1. Choose different key"
def checkKeys(keyA, keyB, mode): )
if keyA == 1 and mode == "encrypt": if keyB == 0:
sys.exit( sys.exit(
"The affine cipher becomes weak when key A is set to 1. Choose different key" "The affine cipher becomes weak when key "
) "B is set to 0. Choose different key"
if keyB == 0 and mode == "encrypt": )
sys.exit(
"The affine cipher becomes weak when key A is set to 1. Choose different key"
)
if keyA < 0 or keyB < 0 or keyB > len(SYMBOLS) - 1: if keyA < 0 or keyB < 0 or keyB > len(SYMBOLS) - 1:
sys.exit( sys.exit(
"Key A must be greater than 0 and key B must be between 0 and %s." "Key A must be greater than 0 and key B must "
% (len(SYMBOLS) - 1) f"be between 0 and {len(SYMBOLS) - 1}."
) )
if cryptoMath.gcd(keyA, len(SYMBOLS)) != 1: if cryptomath.gcd(keyA, len(SYMBOLS)) != 1:
sys.exit( sys.exit(
"Key A %s and the symbol set size %s are not relatively prime. Choose a different key." f"Key A {keyA} and the symbol set size {len(SYMBOLS)} "
% (keyA, len(SYMBOLS)) "are not relatively prime. Choose a different key."
) )
def encryptMessage(key, message): def encrypt_message(key: int, message: str) -> str:
""" """
>>> encryptMessage(4545, 'The affine cipher is a type of monoalphabetic substitution cipher.') >>> encrypt_message(4545, 'The affine cipher is a type of monoalphabetic substitution cipher.')
'VL}p MM{I}p~{HL}Gp{vp pFsH}pxMpyxIx JHL O}F{~pvuOvF{FuF{xIp~{HL}Gi' 'VL}p MM{I}p~{HL}Gp{vp pFsH}pxMpyxIx JHL O}F{~pvuOvF{FuF{xIp~{HL}Gi'
""" """
keyA, keyB = getKeyParts(key) keyA, keyB = divmod(key, len(SYMBOLS))
checkKeys(keyA, keyB, "encrypt") check_keys(keyA, keyB, "encrypt")
cipherText = "" cipherText = ""
for symbol in message: for symbol in message:
if symbol in SYMBOLS: if symbol in SYMBOLS:
@ -61,15 +68,15 @@ def encryptMessage(key, message):
return cipherText return cipherText
def decryptMessage(key, message): def decrypt_message(key: int, message: str) -> str:
""" """
>>> decryptMessage(4545, 'VL}p MM{I}p~{HL}Gp{vp pFsH}pxMpyxIx JHL O}F{~pvuOvF{FuF{xIp~{HL}Gi') >>> decrypt_message(4545, 'VL}p MM{I}p~{HL}Gp{vp pFsH}pxMpyxIx JHL O}F{~pvuOvF{FuF{xIp~{HL}Gi')
'The affine cipher is a type of monoalphabetic substitution cipher.' 'The affine cipher is a type of monoalphabetic substitution cipher.'
""" """
keyA, keyB = getKeyParts(key) keyA, keyB = divmod(key, len(SYMBOLS))
checkKeys(keyA, keyB, "decrypt") check_keys(keyA, keyB, "decrypt")
plainText = "" plainText = ""
modInverseOfkeyA = cryptoMath.findModInverse(keyA, len(SYMBOLS)) modInverseOfkeyA = cryptomath.findModInverse(keyA, len(SYMBOLS))
for symbol in message: for symbol in message:
if symbol in SYMBOLS: if symbol in SYMBOLS:
symIndex = SYMBOLS.find(symbol) symIndex = SYMBOLS.find(symbol)
@ -79,11 +86,11 @@ def decryptMessage(key, message):
return plainText return plainText
def getRandomKey(): def get_random_key():
while True: while True:
keyA = random.randint(2, len(SYMBOLS)) keyA = random.randint(2, len(SYMBOLS))
keyB = random.randint(2, len(SYMBOLS)) keyB = random.randint(2, len(SYMBOLS))
if cryptoMath.gcd(keyA, len(SYMBOLS)) == 1: if cryptomath.gcd(keyA, len(SYMBOLS)) == 1:
return keyA * len(SYMBOLS) + keyB return keyA * len(SYMBOLS) + keyB