For my programming class, I've been instructed to create two programs, each using the same two helper functions: alphabet_position(letter) and rotate_character(char, rot). One function uses the Caesar cipher to encrypt a message with a number of rotations, each given from the command line. The second program is meant to put more use to my Caesar program by turning it into the Vigenere Cipher. Both programs are meant to ignore (i.e., not rotate) special characters and I don't think numbers matter either. However, if the input letter is capitalized, the rotated output letter should be as well.
I've run into several issues with my code: My Caesar program only prints some capital letters. For example, with the arguments Hello, World! and 4, I receive an output of Lipps, svph! and I cannot figure out why that last capital letter isn't printing. When I attempt to pass in pYthon with 26 rotations, my program prints nothing.
My Vigenere program is also doing an odd thing with capital letters: with the passed arguments being Hello, World! and boom, I receive Iszxp, mr!.
Assignment is due in 48 hours and I'm kind of freaking out. 😬 Any and all help, criticism, etc. is welcome!
def alphabet_position(letter):
"""receives a letter and returns the 0-based numerical position of that letter within the alphabet."""
letter = letter.lower()
alphabet = "abcdefghijklmnopqrstuvwxyz"
numerical_pos = alphabet.find(letter)
return numerical_pos
def rotate_character(char, rot):
"""receives a character and an int 'rot', and rotates char by rot number of places to the right."""
alphabet = "abcdefghijklmnopqrstuvwxyz"
alpha_dict = dict(enumerate(alphabet))
new_char = ""
# ignore and return non-alphabetic characters
if char not in alphabet:
return char
# temporarily convert case to locate in alphabet
temp_char = char.lower()
if temp_char in alphabet:
# get original position of letter
orig_pos = alphabet_position(temp_char)
# take char, add rot to its index, mod 25 - 1
new_pos = (int(orig_pos) + int(rot))
if new_pos > 25:
new_pos = (new_pos % 25) - 1
elif new_pos < 0:
# avoid negative index error when rot is 26
new_char = char
# converting new_pos back to alpha
else:
new_char = alpha_dict[new_pos]
# if original char was upper/lower, return corresponding case for new_char
if char.islower():
new_char.lower()
else:
new_char.upper()
return new_char
from helpers import alphabet_position, rotate_character
# ------
# caesar cipher
# ------
def encrypt(text, rot):
new_text = ""
for char in text:
new_char = rotate_character(char, rot)
new_text += str(new_char)
return new_text
def main():
input_text = input("Enter a sentence to encrypt: ")
input_rot = int(input("Number of rotations: "))
print(encrypt(input_text, input_rot))
if __name__ == "__main__":
main()
from helpers import alphabet_position, rotate_character
# ------
# vigenere cipher
# ------
def encrypt(text, rot):
lower_alphabet = "abcdefghijklmnopqrstuvwxyz"
upper_alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
keystream = 0
encrypted = ""
rot.lower()
for i in range(len(text)):
keychar = keystream % len(rot)
if text[i] in lower_alphabet:
new_char = rotate_character(text[i], alphabet_position(rot[keychar]))
new_char.lower()
encrypted += new_char
keystream += 1
elif text[i] in upper_alphabet:
new_char = rotate_character(text[i], alphabet_position(rot[keychar]))
new_char.upper()
encrypted += new_char
keystream += 1
else:
encrypted += text[i]
# stuck around here... vigenere isn't printing shifted capital letters and I
# can't figure out why.
return encrypted
def main():
input_text = input("Enter a sentence to encrypt: ")
input_rot = input("Enter your keyword: ")
print(encrypt(input_text, input_rot))
if __name__ == "__main__":
main()
Edit: helper functions edited to make code cleaner... Now it's only printing the one capital letter when I input pYthon with 4 rotations in Caesar. I'm lost.
Related
def asciiShift(character, aShift):
asciiNum = ord(character) + (int(aShift))%26
return asciiNum
def stringShift(string, shift):
k=0
newstring = ''
string_len = len(string)
while k<string_len:
newstring = newstring + string[int(((int(shift)%int(string_len))+k))%int(string_len)]
k=k+1
if k==string_len:
break
return newstring
def encrypt(message, aShift, sShift):
i=0
length = len(message)
asciiChars = []
while i<length:
asciiChars.append(asciiShift(message[i].upper(), aShift))
i=i+1
if i==length:
break
string = ''
j=0
while j<length:
string = string + str(chr(asciiChars[j]))
j=j+1
shifted_string = stringShift(string, sShift)
print(shifted_string)
def decrypt(message):
x=0
mlength = len(message)
mstring = ''
while x<mlength:
d=0
while d<mlength:
mstring = mstring + message[int(x+d)%(mlength)]
d=d+1
e=0
mstring = mstring.upper()
mlist = []
while e<mlength:
mlist.append(ord(mstring[e]))
e=e+1
f=0
while f<26:
g=0
newstring = ''
while g<mlength:
newstring = newstring + chr(mlist[g] + f%26)
g=g+1
print(newstring)
f=f+1
x=x+1
if x==mlength:
break
# todo list
# shift string around (use.upper())
# convert shifted string to ascii number list
# add numbers from 0-25 to the ascii number list
# print out the results
typeConfirm = input("Encrypt or Decrypt? (E/D): ")
if typeConfirm[0].upper() == 'D':
decryptBool = True
elif typeConfirm[0].upper()== 'E':
decryptBool = False
else:
print("You probably said an incorrect choice or read the question incorrectly. Exiting program for now...")
exit()
if decryptBool == True:
decrypt_msg = input("What is the encoded message?: ")
decrypt(decrypt_msg)
else:
message = input("What is your message?: ")
aShift = input("ASCII shift?: ")
sShift = input("String shift?: ")
a=0
b=len(message)
while a<b:
if message[a] == '~':
print("Sorry, the encryptor doesn't support any special characters (other than the ones on a normal keyboard, or these characters that are on a keyboard: '~', '{', and '}' only these 3 characters in the quotation marks don't work. Sorry for the inconvenience!")
exit()
elif message[a] == '{':
print("Sorry, the encryptor doesn't support any special characters (other than the ones on a normal keyboard, or these characters that are on a keyboard: '~', '{', and '}' only these 3 characters in the quotation marks don't work. Sorry for the inconvenience!")
exit()
elif message[a] == '}':
print("Sorry, the encryptor doesn't support any special characters that aren't on a normal office keyboard. However, these characters that are on a keyboard don't work: '~', '{', and '}' only these 3 characters in the quotation marks don't work. Sorry for the inconvenience!")
exit()
a=a+1
if a==b:
break
encrypt(message, aShift, sShift)
I made this code so far, however for some reason, the decrypter doesn't work with the outputs of the encrypter. (As in, the brute force doesn't output the input at all)
For context, the purpose of this program would be to encrypt a string by converting all the characters to ascii code, and adding a number to it. Then, the new number would be turned back into a character, and the string would be shifted by a certain amount. For ex, "ABC" shift 1 -> [66, 67, 68] -> "BCD" shift 2 -> "DBC"
If someone could help point out why it isn't working (or if there's a better solution, ex. "you wrote this area wrong", or "the encryptor result is faulty", etc.), it would be much appreciated!
Since you indicated you just want to start out with performing a brute force algorithm to decrypt an encrypted phrase or word, the intuitive solution seemed to be to create complimentary functions for the ASCII shift and string shift functions that perform a shift in the opposite direction for the decryption function. Then, build the decryption function such that it is almost a duplicate of the encryption function except it loops through the possible shifting utilizing the complimentary functions.
Following is a revised version of your code you can experiment with.
def asciiShift(character, aShift):
asciiNum = ord(character) + (int(aShift))%26
return asciiNum
def asciiShiftx(character, aShift):
asciiNum = ord(character) - (int(aShift))%26
return asciiNum
def stringShift(string, shift):
k=0
newstring = ''
string_len = len(string)
while k<string_len:
newstring = newstring + string[int(((int(shift)%int(string_len))+k))%int(string_len)]
k=k+1
if k==string_len:
break
return newstring
def stringShiftx(string, shift):
k=0
newstring = ''
string_len = len(string)
while k<string_len:
newstring = newstring + string[int(((int(shift * -1)%int(string_len))+k))%int(string_len)]
k=k+1
if k==string_len:
break
return newstring
def encrypt(message, aShift, sShift):
i=0
length = len(message)
asciiChars = []
while i<length:
asciiChars.append(asciiShift(message[i].upper(), aShift))
i=i+1
if i==length:
break
string = ''
j=0
while j<length:
string = string + str(chr(asciiChars[j]))
j=j+1
shifted_string = stringShift(string, sShift)
print(shifted_string)
def decrypt(message):
for z1 in range(26):
for z2 in range(26):
i=0
lengthx = len(message)
asciiChars = []
while i<lengthx:
asciiChars.append(asciiShiftx(message[i].upper(), z1))
i=i+1
if i==lengthx:
break
string = ''
j=0
while j<lengthx:
string = string + str(chr(asciiChars[j]))
j=j+1
shifted_string = stringShiftx(string, z2)
print('ASCII shift: ', z1, 'String shift: ', z2, shifted_string)
typeConfirm = input("Encrypt or Decrypt? (E/D): ")
if typeConfirm[0].upper() == 'D':
decryptBool = True
elif typeConfirm[0].upper()== 'E':
decryptBool = False
else:
print("You probably said an incorrect choice or read the question incorrectly. Exiting program for now...")
exit()
if decryptBool == True:
decrypt_msg = input("What is the encoded message?: ")
decrypt(decrypt_msg)
else:
message = input("What is your message?: ")
aShift = input("ASCII shift?: ")
sShift = input("String shift?: ")
a=0
b=len(message)
while a<b:
if message[a] == '~':
print("Sorry, the encryptor doesn't support any special characters (other than the ones on a normal keyboard, or these characters that are on a keyboard: '~', '{', and '}' only these 3 characters in the quotation marks don't work. Sorry for the inconvenience!")
exit()
elif message[a] == '{':
print("Sorry, the encryptor doesn't support any special characters (other than the ones on a normal keyboard, or these characters that are on a keyboard: '~', '{', and '}' only these 3 characters in the quotation marks don't work. Sorry for the inconvenience!")
exit()
elif message[a] == '}':
print("Sorry, the encryptor doesn't support any special characters that aren't on a normal office keyboard. However, these characters that are on a keyboard don't work: '~', '{', and '}' only these 3 characters in the quotation marks don't work. Sorry for the inconvenience!")
exit()
a=a+1
if a==b:
break
encrypt(message, aShift, sShift)
I tested this out by encrypting a short phrase ("HELLO THERE") with an ASCII shift of "4" and a string shift of "22".
#Una:~/Python_Programs/Encrypt$ python3 Encrypt.py
Encrypt or Decrypt? (E/D): E
What is your message?: HELLO THERE
ASCII shift?: 4
String shift?: 22
LIPPS$XLIVI
Then, I called the program again and asked it to decrypt the encrypted phrase ("LIPPS$XLIVI"). I will skip to the portion of the terminal output where one can see the original text.
#Una:~/Python_Programs/Encrypt$ python3 Encrypt.py
Encrypt or Decrypt? (E/D): D
What is the encoded message?: LIPPS$XLIVI
. . .
ASCII shift: 4 String shift: 18 O THEREHELL
ASCII shift: 4 String shift: 19 LO THEREHEL
ASCII shift: 4 String shift: 20 LLO THEREHE
ASCII shift: 4 String shift: 21 ELLO THEREH
ASCII shift: 4 String shift: 22 HELLO THERE
ASCII shift: 4 String shift: 23 EHELLO THER
ASCII shift: 4 String shift: 24 REHELLO THE
ASCII shift: 4 String shift: 25 EREHELLO TH
As would make sense the complimentary shift values match the original shift values where one sees the correct decrypted phrase.
Anyway, experiment with that. Hope that helps.
Regards.
I want to write a python function that automatically finds the key of any encrypted text and decrypt the text. I want to use the caesar cipher encryption algorithm.
This code is such that, you will enter the rot but I want the code to be able to find the rot by automatically by itself.
import string
from time import sleep
alphabet = string.ascii_lowercase # "abcdefghijklmnopqrstuvwxyz"
def decrypt(text, rot):
decrypted_text = ""
ct = open("rfc8446.txt", "r")
for cipher in text:
if cipher in alphabet: # check if character is an alphabet
position = alphabet.find(cipher) # find the index position of each text
new_position = (position - rot) % 25 # find the new index position to decrypt
new_character = alphabet[new_position] #
decrypted_text += new_character
else:
decrypted_text += cipher
print(decrypted_text)
text = "hnbcnamjh vh krtn unoc vn knqrwm"
rot = 7
decrypt(text, rot)
this will give you all possible solutions, simply by looping for all rotations.
import string
from time import sleep
def decrypt(text):
for rot in range(26):
alphabet = string.ascii_lowercase # "abcdefghijklmnopqrstuvwxyz"
decrypted_text = ""
for cipher in text:
if cipher in alphabet:
position = alphabet.find(cipher)
new_position = (position - rot) % 25
new_character = alphabet[new_position]
decrypted_text += new_character
else:
decrypted_text += cipher
print(decrypted_text)
text = "hnbcnamjh vh krtn unoc vn knqrwm"
decrypt(text)
however finding the good one is way more complicated since you need to identify which solution "looks" english, using stuff like text plausibility matrices
I am currently working on a school project where I need to build a decrypter for the Vigenere Cipher. The deciphering is working out just fine, but I have a problem which is that every letter is lowercase. I know the reason for this is that my used the casefold() method for my initial string. I did it so I can compare it to the alphabet a-z. Now here is my question: How can I modify the code in so that it will return the corresponding letter in uppercase?
def decipher(key):
original = "Rpoe, Xknf cne Rosvuhcl"
string = original
Alphabet ="abcdefghijklmnopqrstuvwxyz"
dec_message = ""
key = key.lower()
string = string.casefold()
textlength = len(string)
exp_key = key
exp_key_length = len(exp_key)
while exp_key_length < textlength:
exp_key = exp_key + key
exp_key_length = len(exp_key)
key_position = 0
for letter in string:
if letter in Alphabet:
position = Alphabet.find(letter)
key_char = exp_key[key_position]
key_char_position = Alphabet.find(key_char)
key_position += 1
new_position = position - key_char_position
if new_position > 26:
new_position = new_position + 26
new_character = Alphabet[new_position]
dec_message = dec_message + new_character
else:
dec_message = dec_message + letter
print(dec_message)
print(original)
return(dec_message)
decipher("ABC")
I tried to use a for loop so I can look at each letter in the encrypted string and then .upper the letter at the corresponding position in the dec_message string, however, that didn´t work.
The encrypted text is: Rome, Wine and Portugal
I am in an into to Programming class and the assignment is in part to shift the letters of a valid password by +1 if it is a letter or number and -1 if it is a !##$ special character. I have most of it working with my below code but I always get the wrong output for the special characters. If I use to the code of anything high like 128 then I get the wrong symbol.
I am using the code from an encryption program from the other week and slowly changing things but I feel like this is too involved for something simple
If I enter the password UMA#augusta2020 I need to get the output VNB?bvhvtub3131 but I either end up with a space, b, or wrong symbol when I change the code input between 26,64,96,128, etc.
I have updated the code to fix small errors
def main():
print("This program validates and encrypts a password")
print()
main()
# The Encryption Function
def cipher_encrypt(plain_text):
encrypted = ""
for c in plain_text:
if c.isupper(): #check if it's an uppercase character
c_index = ord(c) - ord('A')
# shift the current character by key positions
c_shifted = (c_index + 1) % 26 + ord('A')
c_new = chr(c_shifted)
encrypted += c_new
elif c.islower(): #check if its a lowecase character
c_index = ord(c) - ord('a')
c_shifted = (c_index + 1) % 26 + ord('a')
c_new = chr(c_shifted)
encrypted += c_new
elif c.isdigit():
# if it's a number,shift its value
c_new = (int(c) + 1) % 10
encrypted += str(c_new)
else:
# if its neither alphabetical nor a number, -1
c_shifted = (c_index - 1) % 128 + ord('a')
c_new = chr(c_shifted)
encrypted += c_new
return encrypted
plain_text =input("Enter your Password: ")
print()
ciphertext = cipher_encrypt(plain_text)
print()
print("Your Password: ", plain_text)
print()
print("Your password is valid and encrypted it is: ", ciphertext)
print()
Here is a much cleaner approach:
def cipher_encrypt(plain_text):
alpha = 'abcdefghijklmnopqrstuvwxyz'
digits = '0123456789'
puncs = '!"#$%&\'()*+,-./:;<=>?#[\\]^_`{|}~'
encrypted_text = ''
for c in plain_text:
if c.lower() in alpha:
c_index = alpha.index(c.lower())
e_index = (c_index + 1)%len(alpha)
if c == c.lower():
encrypted_text += alpha[e_index]
else:
encrypted_text += alpha[e_index].upper()
elif c in digits:
c_index = digits.index(c)
e_index = (c_index + 1)%len(digits)
encrypted_text += digits[e_index]
else:
c_index = puncs.index(c)
e_index = (c_index +len(puncs) - 1)%len(puncs)
encrypted_text += puncs[e_index]
return encrypted_text
In this approach I deal with each caharcter in plain text by:
Determining idf the char is part of alpha by making use of the c.lower() function to isolate alpha chars and then find an index modulo the len of alpha. Then I determine if I need an uppercase char or lower case in the encrypted text.
I use the same modulo approach for digits, but don't have to worry about upper and lower, finally
I find the index for the punctuations found in the plain_text
I have a code and I'm having trouble making it interactive.
Here's the problem:
"""Write a function called rot13 that uses the Caesar cipher to encrypt a message. The Caesar cipher works like a substitution cipher but each character is replaced by the character 13 characters to “its right” in the alphabet. So for example the letter “a” becomes the letter “n”. If a letter is past the middle of the alphabet then the counting wraps around to the letter “a” again, so “n” becomes “a”, “o” becomes “b” and so on. Hint: Whenever you talk about things wrapping around its a good idea to think of modulo arithmetic (using the remainder operator)."""
Here's the code to this problem:
def rot13(mess):
alphabet = 'abcdefghijklmnopqrstuvwxyz'
encrypted = ''
for char in mess:
if char == ' ':
encrypted = encrypted + ' '
else:
rotated_index = alphabet.index(char) + 13
if rotated_index < 26:
encrypted = encrypted + alphabet[rotated_index]
else:
encrypted = encrypted + alphabet[rotated_index % 26]
return encrypted
def main():
print(rot13('abcde'))
print(rot13('nopqr'))
print(rot13(rot13('since rot thirteen is symmetric you should see this message')))
if __name__ == "__main__":
main()
I want to make it interactive where you can input any message and you can rotate the letters however many times as you want. Here is my attempt. I understand you'd need two parameters to pass, but I'm clueless as to how to replace a few items.
Here's my attempt:
def rot13(mess, char):
alphabet = 'abcdefghijklmnopqrstuvwxyz'
encrypted = ''
for char in mess:
if char == ' ':
encrypted = encrypted + ' '
else:
rotated_index = alphabet.index(char) + mess
if rotated_index < 26:
encrypted = encrypted + alphabet[rotated_index]
else:
encrypted = encrypted + alphabet[rotated_index % 26]
return encrypted
def main():
messy_shit = input("Rotate by: ")
the_message = input("Type a message")
print(rot13(the_message, messy_shit))
if __name__ == "__main__":
main()
I don't know where my input should be taking place in the function. I have a feeling it could be encrypted?
This is probably what you're looking for. It rotates the message by the messy_shit input.
def rot13(mess, rotate_by):
alphabet = 'abcdefghijklmnopqrstuvwxyz'
encrypted = ''
for char in mess:
if char == ' ':
encrypted = encrypted + ' '
else:
rotated_index = alphabet.index(char) + int(rotate_by)
if rotated_index < 26:
encrypted = encrypted + alphabet[rotated_index]
else:
encrypted = encrypted + alphabet[rotated_index % 26]
return encrypted
def main():
messy_shit = input("Rotate by: ")
the_message = input("Type a message")
print(rot13(the_message, messy_shit))
def rot(message, rotate_by):
'''
Creates a string as the result of rotating the given string
by the given number of characters to rotate by
Args:
message: a string to be rotated by rotate_by characters
rotate_by: a non-negative integer that represents the number
of characters to rotate message by
Returns:
A string representing the given string (message) rotated by
(rotate_by) characters. For example:
rot('hello', 13) returns 'uryyb'
'''
assert isinstance(rotate_by, int) == True
assert (rotate_by >= 0) == True
alphabet = 'abcdefghijklmnopqrstuvwxyz'
rotated_message = []
for char in message:
if char == ' ':
rotated_message.append(char)
else:
rotated_index = alphabet.index(char) + rotate_by
if rotated_index < 26:
rotated_message.append(alphabet[rotated_index])
else:
rotated_message.append(alphabet[rotated_index % 26])
return ''.join(rotated_message)
if __name__ == '__main__':
while True:
# Get user input necessary for executing the rot function
message = input("Enter message here: ")
rotate_by = input("Enter your rotation number: ")
# Ensure the user's input is valid
if not rotate_by.isdigit():
print("Invalid! Expected a non-negative integer to rotate by")
continue
rotated_message = rot(message, int(rotate_by))
print("rot-ified message:", rotated_message)
# Allow the user to decide if they want to continue
run_again = input("Continue? [y/n]: ").lower()
while run_again != 'y' and run_again != 'n':
print("Invalid! Expected 'y' or 'n'")
run_again = input("Continue? [y/n]: ")
if run_again == 'n':
break
Note: It's more efficient to create a list of characters then join them to produce a string instead of using string = string + char. See Method 6 here and the Python docs here. Also, be aware that our rot function only works for lowercase letters of the alphabet. It'll break if you try to rot a message with uppercase characters or any character that isn't in alphabet.