def encrypt(message, key):
""" apply the null cipher, where the key tells at what index the letters of the plaintext should be hidden in each
word* of the encrypted text. the 'words' generated by this function will be 5-letter long strings of randomly-chosen letters
for instance here, are valid encryptions:
- for key=0, HIGH could be encrypted as HITOW IPSLO GOPES HYTER
- for key=2, NOON could be encrypted as TUNDE ODOWT ROOWT PUNDT
"""
message = pre_treat_message(message) # convert to uppercase and remove punctuation
word_substitutes = [] # store the words here
# assemble the disguised message by going through each letter of the plaintext
# and replacing it with a random 5-letter string that has that character in the key position
for c in message:
if c not in ALPHABET: # for our implementation, we won't bother trying to encrypt values not in ALPHABET
continue
# which index of the 5-letter string should match the plaintext?
index_of_plaintext = key % 5 # use the modulo operator so that we can "wrap" large keys into an index that exists in the 5-letter string
# generate a 5-letter string that has random values for all positions except for index_of_plaintext
word_substitute = ''
for i in range(0,5):
if i == index_of_plaintext:
word_substitute += c
else:
# add a randomly-picked letter to word_substitute
replace with code that randomly picks a letter and appends it to word_substitute
word_substitutes.append(word_substitute)
return ' '.join(word_substitutes) # return the words as a single string, with words separated by a space
def decrypt(message, key):
""" apply the null cipher, where the key tells at what index the letters of the plaintext are hidden in each
5-letter 'word' of the encrypted text
"""
message = pre_treat_message(message) # convert to uppercase and remove punctuation
words_in_message = message.split()
return ''.join(word[key % 5] for word in words_in_message)
def decrypt(message, key):
""" apply the null cipher, where the key tells at what index the letters of the plaintext are hidden in each
5-letter 'word' of the encrypted text
"""
message = pre_treat_message(message) # convert to uppercase and remove punctuation
words_in_message = message.split()
decrypted_message = ''
for word in words_in_message:
decrypted_message += word[key % 5] # find the letter whose index is equal to the key
return decrypted_message
def decrypt(message, key):
""" apply the null cipher, where the key tells at what index the letters of the plaintext are hidden in each
5-letter 'word' of the encrypted text
"""
message = pre_treat_message(message) # convert to uppercase and remove punctuation
words_in_message = message.split()
decrypted_message = ''
for word in words_in_message:
decrypted_message += word[replace with logic that computes the index of the plaintext letter] # find the letter whose index is equal to the key
return decrypted_message
def decrypt(message):
message = pre_treat_message(message)
decrypted_message = ''
# assemble the plaintext message by decrypting the message one letter at a time
for c in message:
if c not in ALPHABET:
decrypted_message += c
continue
# find the corresponding decrypted letter and append it to decrypted_message
replace with the logic for decrypting the letter return decrypted_message
def decrypt(message):
message = pre_treat_message(message)
decrypted_message = ''
# assemble the plaintext message by decrypting the message one letter at a time
for c in message:
if c not in ALPHABET:
decrypted_message += c
continue
# find the corresponding decrypted letter and append it to decrypted_message
decrypted_message += ALPHABET[len(ALPHABET)-1-ALPHABET.find(c)]
return decrypted_message
def decrypt(message, key):
message = pre_treat_message(message)
decrypted_message = ''
# assemble the plaintext message by decrypting the message one letter at a time
for c in message:
if c not in ALPHABET:
decrypted_message += c
continue
# find the corresponding decrypted letter and append it to decrypted_message
replace with the logic for decrypting the letter
return decrypted_message
def encrypt(message, key):
message = pre_treat_message(message)
encrypted_message = ''
# assemble the encrypted message by replacing the letters one at a time
for c in message:
if c not in ALPHABET:
encrypted_message += c
continue
index_in_alphabet = ALPHABET.find(c)
shifted_index = replace with the code that finds the index of the letter to use # calculate the index of the substitute letter
encrypted_message += ALPHABET[shifted_index]
return encrypted_message
def decrypt(message):
message = pre_treat_message(message)
decrypted_message = ''
# assemble the plaintext message by decrypting the message one letter at a time
for c in message:
if c not in ALPHABET:
decrypted_message += c
continue
# find the corresponding decrypted letter and append it to decrypted_message
index_in_alphabet = ALPHABET.find(c)
shifted_index = 25 - index_in_alphabet
decrypted_message += ALPHABET[shifted_index]
return decrypted_message
