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DES.py
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DES.py
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#This program is written by Uday Sagar Shiramshetty, studying 3rd year CSE, at MANIT-Bhopal
#It is written according to the python 3 syntax. Just run this program and follow the instructions
#for encryption and decryption
#Any comments may be addressed to udaysagar.2177@gmail.com
from DESCommon import DES, generate_keys
from DESUtil import to_binary, add_pads_if_necessary, hex_to_bin, bin_to_hex, bin_to_text
try:
input = raw_input
except NameError:
pass
def get_bits(plaintext):
text_bits = []
for i in plaintext:
text_bits.extend(to_binary(ord(i)))
return text_bits
def encrypt(plaintext, key_text):
keys = generate_keys(key_text)
text_bits = get_bits(plaintext)
text_bits = add_pads_if_necessary(text_bits)
final_cipher = ''
for i in range(0, len(text_bits), 64):
final_cipher += DES(text_bits, i, (i+64), keys)
# conversion of binary cipher into hex-decimal form
hex_cipher = ''
i = 0
while i < len(final_cipher):
hex_cipher += bin_to_hex(final_cipher[i:i+4])
i = i+4
return hex_cipher
def decrypt(cipher, key_text):
keys = generate_keys(key_text)
text_bits = []
ciphertext = ''
for i in cipher:
# conversion of hex-decimal form to binary form
ciphertext += hex_to_bin(i)
for i in ciphertext:
text_bits.append(int(i))
text_bits = add_pads_if_necessary(text_bits)
keys.reverse()
bin_mess = ''
for i in range(0, len(text_bits), 64):
bin_mess += DES(text_bits, i, (i+64), keys)
i = 0
text_mess = ''
while i < len(bin_mess):
text_mess += bin_to_text(bin_mess[i:i+8])
i = i+8
return text_mess.rstrip('\x00')
def main():
print('Enter the choice')
print('1. ENCRYPT A MESSAGE')
print('2. DECRYPT A MESSAGE')
choice = int(input())
key_text = str(input('Enter the key\n'))
if(len(key_text) < 8):
print('Key must be 8 characters in length. Exiting...')
return
if(choice == 1):
plaintext = str(input('Enter the message(in Text-form)\n'))
cipher = encrypt(plaintext, key_text)
print('the cipher is(in hex-decimal form)')
print(cipher)
else:
cipher = str(input('Enter the message(in hex-decimal form)\n'))
plaintext = decrypt(cipher, key_text)
print('the original text is')
print(plaintext)
print('exiting...')
return
if __name__ == "__main__":
main()