Simple Substitution Cipher Generate Modified Alphabet Key Python

Posted : admin On 18.04.2020

Jan 05, 2019 Tag: cipher Baudot-Murray Code (ITA2). The Affine cipher is a monoalphabetic substitution cipher that uses a simple numeric mapping algorithm to generate a ciphertext alphabet. For the purposes of this explanation we must refer to the indices of alphabetic characters starting from 0. The first is that the Dancing Men cipher is a simple. Get program for caesar cipher in C and C for encryption and decryption. What is Caesar Cipher? It is one of the simplest encryption technique in which each character in plain text is replaced by a character some fixed number of positions down to it.

Simple Substitution Cipher Generate Modified Alphabet Key Python Number
Simple Substitution Cipher Generate Modified Alphabet Key Python Download

vigenere.py

defencrypt(plaintext, key):

key_length=len(key)

key_as_int= [ord(i) foriinkey]

plaintext_int= [ord(i) foriinplaintext]

ciphertext='

foriinrange(len(plaintext_int)):

value= (plaintext_int[i] +key_as_int[i%key_length]) %26

ciphertext+=chr(value+65)

returnciphertext

defdecrypt(ciphertext, key):

key_length=len(key)

key_as_int= [ord(i) foriinkey]

ciphertext_int= [ord(i) foriinciphertext]

plaintext='

foriinrange(len(ciphertext_int)):

value= (ciphertext_int[i] -key_as_int[i%key_length]) %26

plaintext+=chr(value+65)

returnplaintext

commented Jan 3, 2018

I think there are limitations here with lower case and capital letters. You'd need to check for .lower(), and also simply pass the character through if it doesn't match A-Z.

I wrote one that handles all default ASCII characters (95):

For example:

commented Jan 3, 2018•
edited

commented Mar 6, 2018

@flipperbw ,
I'm trying to make a similar program. Would you mind reposting your code with comments; I'm having a bit of a hard time following it.
Thanks.

commented May 1, 2018

I implemented this some years ago, along with a tabula recta generator so you can do it by hand (for fun!)

commented Jan 10, 2020

Hello!
in your first code (the one that starts like:
def vig(txt=', key=', typ='d'):
if not txt:
print 'Needs text')
there is a thing called 'ret_text'
what does it do? I am trying to get inputs and then encode/decode it but I am not sure how I should do that, if only I knew what ret_text does. Can you specify it?
Thanks!

commented Jan 10, 2020

It's just the return text, that one by one figures out the proper character to return given the key. It's been a while since I wrote this snippet but if it can find a match of an ascii character, itll convert that, else it will leave it alone.

vigenere.py

defencrypt(plaintext, key):

key_length=len(key)

key_as_int= [ord(i) foriinkey]

plaintext_int= [ord(i) foriinplaintext]

ciphertext='

foriinrange(len(plaintext_int)):

value= (plaintext_int[i] +key_as_int[i%key_length]) %26

ciphertext+=chr(value+65)

returnciphertext

defdecrypt(ciphertext, key):

key_length=len(key)

key_as_int= [ord(i) foriinkey]

ciphertext_int= [ord(i) foriinciphertext]

plaintext='

foriinrange(len(ciphertext_int)):

value= (ciphertext_int[i] -key_as_int[i%key_length]) %26

plaintext+=chr(value+65)

returnplaintext