def d_SDES(ciphertext, key, mode):
# your code here
modes = ['ECB', 'CBC', 'OFB']
if mode not in modes:
print('Error(d_SDES): undefined mode', end='')
return ''
if not isinstance(ciphertext, str) or len(ciphertext) == 0:
print('Error(d_SDES): Invalid input', end='')
return ''
if len(key) == 0:
if SDES.get_SDES_value('p') == '' or SDES.get_SDES_value(
'q') == '' or SDES.get_SDES_value('key_size') == '':
print('Error(d_SDES): Invalid key', end='')
return ''
key = SDES.generate_key_SDES()
if not utilities.is_binary(key):
print('Error(d_SDES): Invalid key', end='')
return ''
if len(key) != int(SDES.get_SDES_value('key_size')):
print('Error(d_SDES): Invalid key', end='')
return ''
if mode == modes[0]:
return SDES.d_SDES_ECB(ciphertext, key)
elif mode == modes[1]:
return SDES.d_SDES_CBC(ciphertext, key)
else:
return SDES.d_SDES_OFB(ciphertext, key)
def F(Ri,ki):
if utilities.is_binary(ki) and len(Ri)%2 == 0 and len(ki)%2== 0:
expander = expand(Ri)
xor_output = utilities.xor(expander,ki)
mid = len(xor_output)//2
bx1 = xor_output[:mid]
bx2 = xor_output[mid:]
sx1 = sbox1(bx1)
sx2 = sbox2(bx2)
Ri2 = sx1+sx2
return Ri2
elif not utilities.is_binary(ki) or len(ki)%2!= 0:
print('Error(F): invalid key',end='')
return ''
elif len(Ri)%2 != 0:
print('Error(F): invalid input',end='')
return ''
def feistel(bi, ki):
# your code here
if not utilities.is_binary(ki) or len(ki) != int(
get_SDES_value('key_size')) - 1:
print('Error(feistel): Invalid key', end='')
return ''
if not utilities.is_binary(bi) or len(bi) != int(
get_SDES_value('block_size')):
print('Error(feistel): Invalid block', end='')
return ''
after_F = F(bi[int(len(bi) / 2):], ki)
after_xor = utilities.xor(after_F, bi[:int(len(bi) / 2)])
bi2 = bi[int(len(bi) / 2):] + after_xor
return bi2
def expand(R):
# your code here
if not utilities.is_binary(R) or len(R) < 6 or len(R) % 2 != 0:
print('Error(expand): invalid input', end='')
return ''
mid = int(len(R) / 2)
t1 = R[mid - 1]
t2 = R[mid]
output = R[:mid - 1] + t2 + t1 + t2 + t1 + R[mid + 1:]
return output
def decode(b,codeType):
if not utilities.is_binary(b):
print('Error(decode): invalid input',end ='')
return ''
if codeType == 'ASCII':
c = chr(utilities.bin_to_dec(b))
elif codeType == 'B6':
b6 = utilities.get_B6Code()
c = b6[utilities.bin_to_dec(b)]
else:
print('Error(decode): Unsupported Coding Type',end ='')
return ''
return c
def expand(R):
if not utilities.is_binary(R) or len(R)%2 != 0 or utilities.bin_to_dec(R)<6:
print('Error(expand): invalid input',end='')
return ''
else:
mid = int(len(R)/2)-1
i = mid
start = R[0:i]
middle = R[i+1]+R[i]+R[i+1]+R[i]
end = R[i+2:]
output = start+middle+end
return output
def decode_B6(b):
# your code here
if not utilities.is_binary(b):
print('Error(decode_B6): invalid input', end='')
return ''
if len(b) != 6:
print('Error(decode_B6): invalid input', end='')
return ''
b6_code = utilities.get_B6Code()
c = b6_code[utilities.bin_to_dec(b)]
return c
def d_SDES_ECB(ciphertext, key):
# your code here
if not isinstance(ciphertext, str) or len(ciphertext) == 0:
print('Error(d_SDES_ECB): Invalid input', end='')
return ''
if get_SDES_value('encoding_type') == '' or get_SDES_value(
'block_size') == '' or get_SDES_value('key_size') == '':
print('Error(d_SDES_ECB): Invalid configuration', end='')
return ''
if len(key) == 0:
if get_SDES_value('p') == '' or get_SDES_value(
'q') == '' or get_SDES_value('key_size') == '':
print('Error(d_SDES_ECB): Invalid key', end='')
return ''
key = generate_key_SDES()
if not utilities.is_binary(key):
print('Error(d_SDES_ECB): Invalid key', end='')
return ''
if len(key) != int(get_SDES_value('key_size')):
print('Error(d_SDES_ECB): Invalid key', end='')
return ''
undefined = utilities.get_undefined(ciphertext, utilities.get_B6Code())
text = utilities.remove_undefined(ciphertext, utilities.get_B6Code())
size = int(int(get_SDES_value('block_size')) / 6)
blocks = utilities.text_to_blocks(text, size)
plaintext = ''
for block in blocks:
plain_block = ''
for b in block:
plain_block += encode_B6(b)
rounds = int(get_SDES_value('rounds'))
for i in range(rounds):
plain_block = feistel(plain_block, get_subKey(key, rounds - i))
plain_block = plain_block[int(
len(plain_block) / 2):] + plain_block[:int(len(plain_block) / 2)]
b_blocks = utilities.text_to_blocks(plain_block, 6)
for b_b in b_blocks:
plaintext += decode_B6(b_b)
while plaintext[-1] == 'Q':
plaintext = plaintext[:-1]
plaintext = utilities.insert_undefinedList(plaintext, undefined)
return plaintext
def e_SDES_ECB(plaintext, key):
# your code here
if not isinstance(plaintext, str) or len(plaintext) == 0:
print('Error(e_SDES_ECB): Invalid input', end='')
return ''
if get_SDES_value('encoding_type') == '' or get_SDES_value(
'block_size') == '' or get_SDES_value('key_size') == '':
print('Error(e_SDES_ECB): Invalid configuration', end='')
return ''
if len(key) == 0:
if get_SDES_value('p') == '' or get_SDES_value(
'q') == '' or get_SDES_value('key_size') == '':
print('Error(e_SDES_ECB): Invalid key', end='')
return ''
key = generate_key_SDES()
if not utilities.is_binary(key):
print('Error(e_SDES_ECB): Invalid key', end='')
return ''
if len(key) != int(get_SDES_value('key_size')):
print('Error(e_SDES_ECB): Invalid key', end='')
return ''
undefined = utilities.get_undefined(plaintext, utilities.get_B6Code())
text = utilities.remove_undefined(plaintext, utilities.get_B6Code())
size = int(int(get_SDES_value('block_size')) / 6)
blocks = utilities.text_to_blocks(text, size)
while len(blocks[-1]) != size:
blocks[-1] += 'Q'
ciphertext = ''
for block in blocks:
cipher_block = ''
for b in block:
cipher_block += encode_B6(b)
for i in range(int(get_SDES_value('rounds'))):
cipher_block = feistel(cipher_block, get_subKey(key, i + 1))
cipher_block = cipher_block[
int(len(cipher_block) /
2):] + cipher_block[:int(len(cipher_block) / 2)]
b_blocks = utilities.text_to_blocks(cipher_block, 6)
for b_b in b_blocks:
ciphertext += decode_B6(b_b)
ciphertext = utilities.insert_undefinedList(ciphertext, undefined)
return ciphertext
def get_subKey(key,i):
key_size = int(get_SDES_value('key_size'))
if not utilities.is_binary(key) or len(key) != key_size:
print('Error(get_subKey): Invalid key',end='')
return ''
elif not isinstance(i, int) or i <= 0:
print('Error(get_subKey): invalid i',end='')
return ''
else:
i-=1
leftA = key[0:i]
leftB = key[i:]
subKey = leftB+leftA
subKey = subKey[:len(subKey)-1]
return subKey
def F(Ri, ki):
# your code here
if not utilities.is_binary(ki):
print('Error(F): invalid key', end='')
return ''
if len(ki) != int(get_SDES_value('key_size')) - 1:
print('Error(F): invalid key', end='')
return ''
if not utilities.is_binary(Ri):
print('Error(F): invalid input', end='')
return ''
if len(Ri) != int(get_SDES_value('block_size')) / 2:
print('Error(F): invalid input', end='')
return ''
expanded = expand(Ri)
xored = utilities.xor(expanded, ki)
b1 = sbox1(xored[:int(len(xored) / 2)])
b2 = sbox2(xored[int(len(xored) / 2):])
Ri2 = b1 + b2
return Ri2
def feistel(bi,ki):
if len(bi)%2!= 0:
print('Error(feistel): Invalid block',end='')
return ''
elif not utilities.is_binary(ki) or len(ki)%2!= 0:
print('Error(feistel): Invalid key',end='')
return ''
else:
# print(bi, ki)
m = int(len(bi)//2)
Li = bi[:m]
Ri = bi[m:]
Li1 = Ri
Ri1 = utilities.xor(Li, F(Ri,ki))
bi2 = Li1 + Ri1
return bi2
def decode(b, codeType):
# your code here
if not utilities.is_binary(b):
print('Error(decode): invalid input', end='')
return ''
if not isinstance(codeType, str):
print('Error(decode): Unsupported Coding Type', end='')
return ''
if str(codeType) != 'B6' and str(codeType) != 'ASCII':
print('Error(decode): Unsupported Coding Type', end='')
return ''
if codeType == 'ASCII':
c = chr(utilities.bin_to_dec(b))
else:
c = decode_B6(b)
return c
def get_subKey(key, i):
# your code here
if not utilities.is_binary(key):
print('Error(get_subKey): Invalid key', end='')
return ''
if len(key) != int(get_SDES_value('key_size')):
print('Error(get_subKey): Invalid key', end='')
return ''
if not isinstance(i, int):
print('Error(get_subKey): invalid i', end='')
return ''
if i <= 0:
print('Error(get_subKey): invalid i', end='')
return ''
if i == 1:
subKey = key[:-1]
else:
subKey = key[i - 1:] + key[:i - 2]
return subKey
def sbox2(R):
# your code here
if get_SDES_value('block_size') == '':
print('Error(sbox2): undefined block size', end='')
return ''
if not utilities.is_binary(R):
print('Error(sbox2): invalid input', end='')
return ''
if len(R) != int(int(get_SDES_value('block_size')) / 4 + 1):
print('Error(sbox2): invalid input', end='')
return ''
sbox2_file = open(sbox2File, 'r')
sbox2_list = sbox2_file.read().split('\n')
if len(R) - 1 > len(sbox2_list):
print('Error(sbox2): undefined sbox2', end='')
return ''
box_2d = []
for box in sbox2_list:
box = box[box.find(':') + 1:]
box_2d.append(box.split(','))
row = int(utilities.bin_to_dec(R[0]))
column = int(utilities.bin_to_dec(R[1:]))
temp = 2**(len(R) - 1)
try:
output = box_2d[len(R) - 2][row * temp + column]
except IndexError:
print('Error(sbox2): undefined sbox2', end='')
return ''
return output
