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c-transposition.py
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c-transposition.py
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import time
import math
# Encryption and Decryption functions for Columnar Transposition
def columnar_transposition_encrypt(text, key):
cipher = ""
k_indx = 0
msg_len = float(len(text))
msg_lst = list(text)
key_lst = sorted(list(key))
col = len(key)
row = int(math.ceil(msg_len / col))
fill_null = int((row * col) - msg_len)
msg_lst.extend('_' * fill_null)
matrix = [msg_lst[i: i + col] for i in range(0, len(msg_lst), col)]
for _ in range(col):
curr_idx = key.index(key_lst[k_indx])
cipher += ''.join([row[curr_idx] for row in matrix])
k_indx += 1
return cipher
def columnar_transposition_decrypt(text, key):
msg = ""
k_indx = 0
msg_indx = 0
msg_len = float(len(text))
msg_lst = list(text)
col = len(key)
row = int(math.ceil(msg_len / col))
key_lst = sorted(list(key))
dec_cipher = []
for _ in range(row):
dec_cipher += [[None] * col]
for _ in range(col):
curr_idx = key.index(key_lst[k_indx])
for j in range(row):
dec_cipher[j][curr_idx] = msg_lst[msg_indx]
msg_indx += 1
k_indx += 1
try:
msg = ''.join(sum(dec_cipher, []))
except TypeError:
raise TypeError("This program cannot", "handle repeating words.")
null_count = msg.count('_')
if null_count > 0:
return msg[:-null_count]
return msg
def main_columnar_transposition():
key = input("Enter the Columnar Transposition key: ")
message = input("Enter the message to encrypt: ")
# Encryption
start_time = time.time()
encrypted_message = columnar_transposition_encrypt(message, key)
encryption_time = time.time() - start_time
print(f"Encrypted message: {encrypted_message}")
print(f"Encryption time: {encryption_time:.6f} seconds")
decrypt_choice = input("Do you want to decrypt the message? (y/n): ")
if decrypt_choice.lower() == 'y':
encrypted_message = input("Enter the encrypted message: ")
# Decryption
start_time = time.time()
decrypted_message = columnar_transposition_decrypt(encrypted_message, key)
decryption_time = time.time() - start_time
print(f"Decrypted message: {decrypted_message}")
print(f"Decryption time: {decryption_time:.6f} seconds")
avg_time = (encryption_time + decryption_time) / 2 if decrypt_choice.lower() == 'y' else encryption_time
print(f"Average time for encryption and decryption: {avg_time:.6f} seconds")
if __name__ == "__main__":
main_columnar_transposition()