mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-10-05 21:29:29 +00:00
583a614fef
* Deleted greatest_common_divisor def from many files and instead imported the method from Maths folder * Deleted greatest_common_divisor def from many files and instead imported the method from Maths folder, also fixed comments * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Deleted greatest_common_divisor def from many files and instead imported the method from Maths folder, also fixed comments * Imports organized * recursive gcd function implementation rolledback * more gcd duplicates removed * more gcd duplicates removed * Update maths/carmichael_number.py * updated files * moved a file to another location --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
110 lines
3.4 KiB
Python
110 lines
3.4 KiB
Python
import random
|
|
import sys
|
|
|
|
from maths.greatest_common_divisor import gcd_by_iterative
|
|
|
|
from . import cryptomath_module as cryptomath
|
|
|
|
SYMBOLS = (
|
|
r""" !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`"""
|
|
r"""abcdefghijklmnopqrstuvwxyz{|}~"""
|
|
)
|
|
|
|
|
|
def check_keys(key_a: int, key_b: int, mode: str) -> None:
|
|
if mode == "encrypt":
|
|
if key_a == 1:
|
|
sys.exit(
|
|
"The affine cipher becomes weak when key "
|
|
"A is set to 1. Choose different key"
|
|
)
|
|
if key_b == 0:
|
|
sys.exit(
|
|
"The affine cipher becomes weak when key "
|
|
"B is set to 0. Choose different key"
|
|
)
|
|
if key_a < 0 or key_b < 0 or key_b > len(SYMBOLS) - 1:
|
|
sys.exit(
|
|
"Key A must be greater than 0 and key B must "
|
|
f"be between 0 and {len(SYMBOLS) - 1}."
|
|
)
|
|
if gcd_by_iterative(key_a, len(SYMBOLS)) != 1:
|
|
sys.exit(
|
|
f"Key A {key_a} and the symbol set size {len(SYMBOLS)} "
|
|
"are not relatively prime. Choose a different key."
|
|
)
|
|
|
|
|
|
def encrypt_message(key: int, message: str) -> str:
|
|
"""
|
|
>>> 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'
|
|
"""
|
|
key_a, key_b = divmod(key, len(SYMBOLS))
|
|
check_keys(key_a, key_b, "encrypt")
|
|
cipher_text = ""
|
|
for symbol in message:
|
|
if symbol in SYMBOLS:
|
|
sym_index = SYMBOLS.find(symbol)
|
|
cipher_text += SYMBOLS[(sym_index * key_a + key_b) % len(SYMBOLS)]
|
|
else:
|
|
cipher_text += symbol
|
|
return cipher_text
|
|
|
|
|
|
def decrypt_message(key: int, message: str) -> str:
|
|
"""
|
|
>>> 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.'
|
|
"""
|
|
key_a, key_b = divmod(key, len(SYMBOLS))
|
|
check_keys(key_a, key_b, "decrypt")
|
|
plain_text = ""
|
|
mod_inverse_of_key_a = cryptomath.find_mod_inverse(key_a, len(SYMBOLS))
|
|
for symbol in message:
|
|
if symbol in SYMBOLS:
|
|
sym_index = SYMBOLS.find(symbol)
|
|
plain_text += SYMBOLS[
|
|
(sym_index - key_b) * mod_inverse_of_key_a % len(SYMBOLS)
|
|
]
|
|
else:
|
|
plain_text += symbol
|
|
return plain_text
|
|
|
|
|
|
def get_random_key() -> int:
|
|
while True:
|
|
key_b = random.randint(2, len(SYMBOLS))
|
|
key_b = random.randint(2, len(SYMBOLS))
|
|
if gcd_by_iterative(key_b, len(SYMBOLS)) == 1 and key_b % len(SYMBOLS) != 0:
|
|
return key_b * len(SYMBOLS) + key_b
|
|
|
|
|
|
def main() -> None:
|
|
"""
|
|
>>> key = get_random_key()
|
|
>>> 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.startswith("e"):
|
|
mode = "encrypt"
|
|
translated = encrypt_message(key, message)
|
|
elif mode.startswith("d"):
|
|
mode = "decrypt"
|
|
translated = decrypt_message(key, message)
|
|
print(f"\n{mode.title()}ed text: \n{translated}")
|
|
|
|
|
|
if __name__ == "__main__":
|
|
import doctest
|
|
|
|
doctest.testmod()
|
|
# main()
|