Having issues Decrpyting ciphertext using own alphabet string (python)

Question

I have it set to ask the user a word to encrpyt which works fine using my own alphabet.

My issue is trying to also get it to return the deciphered text.

So far I have it either returning the encrypted message twice or sending back a different version of the encrypted message.

I have tried using - instead of + in my for char, and it gives me a error which I thought was the correct way to do it.

alphabet = "abcdefghijklmnopqrstuvwxyz"
key      = "zjrekydnqoluaxmicvpgtfbhws"


def decryptMessage(ciphertext, key):
    
    plaintext = ""
    for char in ciphertext:
        
        if alphabet.find(char) < +1:
             plaintext += key[alphabet.find(char)]
        else:
                 plaintext += char
    
    
    return plaintext


def encryptMessage(plaintext, key):
   
    ciphertext = ""

    
    for char in plaintext:
       
        if alphabet.find(char) > -1:
            ciphertext += key[alphabet.find(char)]
        else:
            ciphertext += char
    
    
    return ciphertext


message = input("Type a message to encrypt: ")


encrypted = encryptMessage(message, key)


decrypted = decryptMessage(encrypted, key)


print("Plaintext message: " + message)
print("Encrypted message: " + encrypted)
print("Decrypted message: " + decrypted)

Joran Beasley · Accepted Answer · 2022-10-09 22:52:09Z

3

you should use the builtin str.translate

message = "hello world"
alphabet = b"abcdefghijklmnopqrstuvwxyz"
key      = b"zjrekydnqoluaxmicvpgtfbhws"
encrypted = message.translate(dict(zip(alphabet,key)))
print("E:",encrypted)
decrypted = encrypted.translate(dict(zip(key,alphabet)))
print("D:",decrypted)

answered Oct 9, 2022 at 22:52

Joran Beasley

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Comments

ScottC · Accepted Answer · 2022-10-10 00:48:39Z

2

If you want to keep with the theme of your original code:

You need to modify as follows:

alphabet = "abcdefghijklmnopqrstuvwxyz"
key      = "zjrekydnqoluaxmicvpgtfbhws"


def decryptMessage(ciphertext, key):
    
    plaintext = ""
    for char in ciphertext:
        
        if key.find(char) > -1:
             plaintext += alphabet[key.find(char)]
        else:
             plaintext += char
    
    return plaintext


def encryptMessage(plaintext, key):
   
    ciphertext = ""
    for char in plaintext:
       
        if alphabet.find(char) > -1:
            ciphertext += key[alphabet.find(char)]
        else:
            ciphertext += char
    
    return ciphertext

message = input("Type a message to encrypt: ")
encrypted = encryptMessage(message, key)
decrypted = decryptMessage(encrypted, key)

print("Plaintext message: " + message)
print("Encrypted message: " + encrypted)
print("Decrypted message: " + decrypted)

edited Oct 10, 2022 at 0:48

answered Oct 9, 2022 at 22:53

ScottC

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2 Comments

Tydus X Over a year ago

Thank you, this solved my problem. I can't believe it was right under my eyes the entire time haha.

ScottC Over a year ago

@DamanVanSteenis - hidden in plain sight :)

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