def cryptanalysis_xshift(ciphertext):
# your code here
wordList = utilities.text_to_words(ciphertext)
single = list()
for word in wordList:
if len(word) == 1 and word not in single:
single.append(word)
shiftStringList = utilities.get_shiftStringList()
for s in single:
for shiftString in shiftStringList:
now_c = shiftString.index(s)
ori_c = shiftString.index('I')
dis = now_c - ori_c if now_c > ori_c else now_c - ori_c + 52
plaintext = d_xshift(ciphertext, (shiftString, dis))
if utilities.is_plaintext(plaintext, 'engmix.txt', 0.90):
utilities.text_to_file(plaintext, 'plaintext_Jiayao_Pang_q2.txt')
return (shiftString, dis), plaintext
key = ('', 0)
plaintext = ''
return key, plaintext
def cryptanalysis_substitution(ciphertext):
key = '''smzokelxrcitbudnhwfpyaqvjg':"!-; ,#?.''' # <--- change this line with your key
key = utilities.adjust_key(key) # <--- keep this line
# add lines to decrypt the ciphertext
plaintext = d_substitution(ciphertext, key)
# remember to write your plaintext to file
utilities.text_to_file(plaintext, 'plaintext_Jiayao_Pang_q3.txt')
return key, plaintext
def cryptanalysis_vigenere(ciphertext):
# yoru code here
FriedmanL = utilities.getKeyL_friedman(ciphertext)
ShiftL = utilities.getKeyL_shift(ciphertext)
non_alpha = utilities.get_nonalpha(ciphertext)
if ShiftL != 1:
# try every possible size
start = min(FriedmanL, ShiftL)
if start >= 3:
start -= 1
end = max(FriedmanL, ShiftL) + 2
modified = utilities.remove_nonalpha(ciphertext)
for size in range(start, end):
plaintext = ''
shiftList = []
blocks = utilities.text_to_blocks(modified, size)
baskets = utilities.blocks_to_baskets(blocks)
for element in baskets:
# get the list of chi_squared for every shift
chiList = [round(utilities.get_chiSquared(utilities.d_shift(element, (i, 'l'))), 4)
for i in range(26)]
shiftList.append(chiList.index(min(chiList)))
for i in range(len(baskets)):
baskets[i] = utilities.d_shift(baskets[i], (shiftList[i], 'l'))
result = utilities.blocks_to_baskets(baskets)
for e in result:
plaintext += e
plaintext = utilities.insert_nonalpha(plaintext, non_alpha)
if utilities.is_plaintext(plaintext, 'engmix.txt', 0.90):
plain = utilities.remove_nonalpha(plaintext)[:size]
key = ''
v_square = utilities.get_vigenereSquare()
counter = 0
for pChar in plain:
pIndex = v_square[0].index(pChar)
kIndex = v_square[pIndex].index(blocks[0][counter])
counter += 1
key += v_square[0][kIndex]
utilities.text_to_file(plaintext, 'plaintext_Jiayao_Pang_q4.txt')
return key, plaintext
key = 0
plaintext = ''
return key, plaintext
def q4A(ciphertext):
# your code here
print(
'Provide your description here:\n'
'The ciphertext is all numbers --> the second step would be Polybius.\n'
'After decryption of Polybius, I start to decrypt the new cipher with easier ways.\n'
'First Atbash --> is_plaintext() is False\n'
'Second Shift Cryptanalysis --> False.\n'
'Third Columnar Transposition(only with key \'ba\') --> True\n'
'The result is: Columnar Transposition + Polybius') # <----- edit this
plaintext, (key2, key1) = q4.d_type1(ciphertext)
utilities.text_to_file(plaintext, 'q4A_plaintext.txt')
return plaintext, (key1, key2)
def q4C(ciphertext):
# your code here
print(
'Provide your description here:\n'
'All the characters of the ciphertext are upper case --> It must be Hill Cipher.\n'
'I have writen a simple cryptanalysis function.\n'
'I constructed all the 2by2 matrix which are invertible. And after I got each new cipher,\n'
'I tried all the possible 3 ways:\n'
' Atbash & Columnar Transposition & Shift\n'
' It can\'t be Polybius since there is no numbers.'
'The cryptanalysis has failed for the first 2 ways but returned the right text for Shift Cipher.\n'
'The result is: Shift + Hill') # <----- edit this
plaintext, (key2, key1) = q4.d_type3(ciphertext)
utilities.text_to_file(plaintext, 'q4C_plaintext.txt')
return plaintext, (key1, key2)
def q4B(ciphertext):
# your code here
print(
'Provide your description here:\n'
'There are so many \'q\'s in the ciphertext. The only way of encryption with\n'
'padding q is Columnar Transposition.\n'
'The new cipher can not be Polybius (not numbers).\n'
'It can not be Hill cipher since Columnar Transposition does not change cases of letters.\n'
'So, I still start from the easier ways.\n'
'First Atbash --> is_plaintext() is False\n'
'Second Shift Cryptanalysis --> True.\n'
'The result is: Shift + Columnar Transposition') # <----- edit this
plaintext, (key2, key1) = q4.d_type2(ciphertext)
utilities.text_to_file(plaintext, 'q4B_plaintext.txt')
return plaintext, (key1, key2)
def task3():
print('{}'.format('-' * 40))
print("Start of Task 3: Scytale Cipher Testing")
print()
print('--------- Testing Encryption:')
for i in range(3, 7):
plainfile = 'plaintext1' + str(i - 2) + '.txt'
plaintext = utilities.file_to_text(plainfile)
ciphertext = A1_solution.e_scytale(plaintext, i)
print('key = {}'.format(i))
print('ciphertext: ')
print(ciphertext)
utilities.text_to_file(ciphertext, 'ciphertext3' + str(i - 2) + '.txt')
print()
print('-------- Testing Decryption: ')
for i in range(3, 7):
ciphertext = utilities.file_to_text('ciphertext3' + str(i - 2) +
'.txt')
plaintext = A1_solution.d_scytale(ciphertext, i)
print('key = {}'.format(i))
print('plaintext: ')
print(plaintext)
print()
print('-------- Testing Cryptanalysis: ')
for i in range(5, 7):
file = 'ciphertext3' + str(i) + '.txt'
ciphertext = utilities.file_to_text(file)
key, plaintext = A1_solution.cryptanalysis_scytale(ciphertext)
print('key = {}'.format(key), end=' , ')
if plaintext == utilities.file_to_text('plaintext31.txt'):
print('Plaintext verified')
else:
print('Plaintext mismatch')
print()
print('End of Task 3: Scytale Cipher Testing')
print('{}'.format('-' * 40))
print()
return
def task2():
print('{}'.format('-' * 40))
print("Start of Task 2: Extended Atbash Testing")
print()
print('-------- Testing Encryption: ')
plaintext = utilities.file_to_text('plaintext14.txt')
for i in range(5):
ciphertext = A1_solution.e_eatbash(plaintext, i + 5)
print('key = {}'.format(i))
print('ciphertext: ')
print(ciphertext)
utilities.text_to_file(ciphertext, 'ciphertext2' + str(i + 1) + '.txt')
print()
print('-------- Testing Decryption: ')
for i in range(5):
ciphertext = utilities.file_to_text('ciphertext2' + str(i + 1) +
'.txt')
plaintext = A1_solution.d_eatbash(ciphertext, i)
print('key = {}'.format(i))
print('plaintext: ')
print(plaintext)
print()
print('-------- Testing Cryptanalysis: ')
for i in range(5):
file = 'ciphertext2' + str(i + 1) + '.txt'
ciphertext = utilities.file_to_text(file)
key, plaintext = A1_solution.cryptanalysis_eatbash(ciphertext)
print('key = {}'.format(key), end=' , ')
if plaintext == utilities.file_to_text('plaintext14.txt'):
print('Plaintext verified')
else:
print('Plaintext mismatch')
print()
print('End of Task 2: Extended Atbash Testing')
print('{}'.format('-' * 40))
print()
return
def cryptanalysis_xcrypt(ciphertext):
# your code here
if ciphertext[-1] == 'q':
lastIndex = ciphertext.rfind('q')
Index = ciphertext.rfind('q', 0, lastIndex)
possibleKey = len(ciphertext) / (lastIndex - Index)
plaintext = d_xcrypt(ciphertext, possibleKey)
if utilities.is_plaintext(plaintext, 'engmix.txt', 0.90):
utilities.text_to_file(plaintext, 'plaintext_Jiayao_Pang_q1.txt')
return int(possibleKey), plaintext
found = False
for i in range(1, 501):
plaintext = d_xcrypt(ciphertext, i)
if utilities.is_plaintext(plaintext, 'engmix.txt', 0.90):
found = True
break
if found is False:
return 0, ''
utilities.text_to_file(plaintext, 'plaintext_Jiayao_Pang_q1.txt')
return i, plaintext
def task4():
print('{}'.format('-' * 40))
print("Start of Task 4: Polybius Square Cipher Testing")
print()
print('-------- Testing get_polybius_square:')
print('start = "A", size = 5: {}'.format(
A1_solution.get_polybius_square('A', 5)))
print('start = "R", size = 6: {}'.format(
A1_solution.get_polybius_square('R', 6)))
print('start = "@", size = 7: {}'.format(
A1_solution.get_polybius_square('@', 7)))
print('start = "A", size = 5: {}'.format(
A1_solution.get_polybius_square('A', 5)))
print('start = " ", size = 8: {}'.format(
A1_solution.get_polybius_square(' ', 8)))
print('start = "+", size = 9: {}'.format(
A1_solution.get_polybius_square('+', 9)))
print('start = " ", size = 10: {}'.format(
A1_solution.get_polybius_square(' ', 10)))
print()
print('-------- Testing Encryption:')
start = ['D', 'A', ' ', '+', 'B']
for i in range(1, 6):
plainfile = 'plaintext4' + str(i) + '.txt'
plaintext = utilities.file_to_text(plainfile)
key = (start[i - 1], i + 5)
ciphertext = A1_solution.e_polybius(plaintext, key)
print('key = {}'.format(key))
print('ciphertext: ')
print(ciphertext)
utilities.text_to_file(ciphertext, 'ciphertext4' + str(i) + '.txt')
print()
print('-------- Testing Decryption: ')
for i in range(1, 6):
ciphertext = utilities.file_to_text('ciphertext4' + str(i) + '.txt')
key = (start[i - 1], i + 5)
plaintext = A1_solution.d_polybius(ciphertext, key)
print('key = {}'.format(key))
print('plaintext: ')
print(plaintext)
print()
print('-------- Testing Cryptanalysis: ')
size = [6, 9, 8]
for i in range(6, 9):
file = 'ciphertext4' + str(i) + '.txt'
ciphertext = utilities.file_to_text(file)
key, plaintext = A1_solution.cryptanalysis_polybius(
ciphertext, size[i - 6])
print('key = {} --> {}'.format(
key, A1_solution.get_polybius_square(key[0], key[1])),
end=' , ')
if plaintext == utilities.file_to_text('plaintext46.txt'):
print('Plaintext verified')
else:
print('Plaintext mismatch')
print()
print('End of Task 4: Polybius Square Cipher Testing')
print('{}'.format('-' * 40))
print()
return