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baconscipher.py
def encipher(plaintext, target_text):
"""
Encipher plaintext to target text with binary 0
as lower case and binary 1 as upper case
"""
# remove all non-alphabetic characters
# from plaintext and convert to upper case
plaintext = ''.join([c for c in plaintext if c.isalpha()]).upper()
# get a string of 0s and 1s representing the
# formatting of the enciphered message letters
binary_string = _string_to_bit_pattern(plaintext)
# format the target text letters as upper or lower case
# according to the bit pattern
enciphered = _cased_text_from_bit_pattern(target_text, binary_string)
return enciphered
def decipher(enciphered):
"""
Decipher enciphered text assuming lower case letters
represent binary 0 and upper case letters represent binary 1
"""
print("\nDeciphering\n===========\n")
# remove everything except letters
enciphered = ''.join([c for c in enciphered if c.isalpha()])
length = len(enciphered)
letter_quintet = ""
bit_pattern = ""
deciphered = []
for i in range(0, length, 5):
# grab next 5 letters
letter_quintet = enciphered[i: i+5]
# get corresponding string of 5 bits
bit_pattern = _letter_quintet_to_bit_pattern(letter_quintet)
# get letter corresponding to bit pattern
letter = chr(int(bit_pattern, 2) + 65)
print(f"{letter_quintet} {bit_pattern} {letter}")
deciphered.append(letter)
return "".join(deciphered)
#------------------------------------------------------------
# "PRIVATE" FUNCTIONS
#------------------------------------------------------------
def _string_to_bit_pattern(string):
"""
Convert string of letters to string of
corresponding 5-bit patterns
"""
binary_list = []
bit_pattern = ""
for letter in string:
# get ASCII code, subtract 65 and format as 5 bit string
bit_pattern = format(ord(letter) - 65, '05b')
binary_list.append(bit_pattern)
return "".join(binary_list)
def _cased_text_from_bit_pattern(target_text, binary_pattern):
"""
Set case of target text according to string of 5-bit patterns
0 => lower case
1 => upper case
Non-alpha characters are skipped
"""
cased_text = []
index = 0
for bit in binary_pattern:
while not target_text[index].isalpha():
cased_text.append(target_text[index])
index += 1
if bit == "0":
cased_text.append(target_text[index].lower())
else:
cased_text.append(target_text[index].upper())
index += 1
return "".join(cased_text)
def _letter_quintet_to_bit_pattern(letter_quintet):
"""
Convert string of 5 letters to corresponding bit pattern
Lower case => 0
Upper case => 1
"""
bit_pattern = []
for c in letter_quintet:
if(c >= "a" and c <= "z"):
bit_pattern.append("0")
elif(c >= "A" and c <= "Z"):
bit_pattern.append("1")
return "".join(bit_pattern)
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