I am trying to read a string encrypt it save it to a text file then read the text file read the encrypted string decrypt it in python

Question

I am trying to read a string encrypt it save it to a text file then read the text file read the encrypted string decrypt it in python, I am using cryptography library, I think the error is because of python lists adding ["string"] at the beginning and at the end,i also tried converting the read list into binary but it takes it as b["b'key'"],any ideas

def write_key():                                #creating a key
    key = Fernet.generate_key()
    with open("key.key", "wb") as key_file:
        key_file.write(key)

def load_key():                                 #reading the generated key
    return open("key.key", "rb").read()

data = input()
data = bytes(data,'utf-8')                      #you cannot encrypt str do converting it to bytes
write_key()                                     #creating the key
key = load_key()                                #loading the key
f = Fernet(key)
encrypted = f.encrypt(data)                     #encrypting the data
print(encrypted)

file = open("encrypted.txt", "w")               #writing the encrypted the data       
file.write("%s\n" %(encrypted))
file.close()

with open("encrypted.txt", "r") as f:           #reading the encrypted the data
    rdata = [line.rstrip('\n') for line in f]    #removing \n as it is added while saving the txt file
print(rdata)


key = load_key()
f = Fernet(key)
decrypted_encrypted = f.decrypt(rdata)
print(decrypted_encrypted)

Output i get:

Enter the secret message: YOUR MESSAGE
Printing the encrypted message after encryption b'gAAAAABfWdNG64dvT-tpQA1EA-zYC8lsC4hL9EoZ0e008BMIWikfafT_FOmLyjWJh2dinGG8oi6VI16XCpwB1H4AZE2sk-ZgJQ=='
Printing the encrypted message after reading it from the txt file ["b'gAAAAABfWdNG64dvT-tpQA1EA-zYC8lsC4hL9EoZ0e008BMIWikfafT_FOmLyjWJh2dinGG8oi6VI16XCpwB1H4AZE2sk-ZgJQ=='"]
Traceback (most recent call last):

  File "C:\Users\Documents\Projects\temp.py", line 31, in <module>
    decrypted_encrypted = f.decrypt(rdata)

  File "C:\Users\anaconda3\lib\site-packages\cryptography\fernet.py", line 74, in decrypt
    timestamp, data = Fernet._get_unverified_token_data(token)

  File "C:\Users\anaconda3\lib\site-packages\cryptography\fernet.py", line 85, in _get_unverified_token_data
    utils._check_bytes("token", token)

  File "C:\Users\anaconda3\lib\site-packages\cryptography\utils.py", line 31, in _check_bytes
    raise TypeError("{} must be bytes".format(name))

TypeError: token must be bytes

load_key is a function with gives back the save key for decryption — Prajwal Megalamani, Sep 10 '20 at 13:03

Liju · Accepted Answer · 2020-09-10T13:03:38.793

Data passed to decrypt should be bytes not strings. Hence this issue.
While reading and writing from encrypted.txt use respective binary mode as below.

def write_key():                                #creating a key
    key = Fernet.generate_key()
    with open("key.key", "wb") as key_file:
        key_file.write(key)

def load_key():                                 #reading the generated key
    return open("key.key", "rb").read()

data = input()
data = bytes(data,'utf-8')                      #you cannot encrypt str do converting it to bytes
write_key()                                     #creating the key
key = load_key()                                #loading the key
f = Fernet(key)
encrypted = f.encrypt(data)                     #encrypting the data

file = open("encrypted.txt", "wb")               #writing the encrypted the data       
file.write(encrypted)
file.close()

with open("encrypted.txt", "rb") as f:           #reading the encrypted the data
    rdata =f.read()

key = load_key()
f = Fernet(key)
decrypted_encrypted = f.decrypt(rdata)
print(decrypted_encrypted)

Thanks it worked but i also find a alternative by writing it to a binary file directly — Prajwal Megalamani, Sep 10 '20 at 13:02

I am trying to read a string encrypt it save it to a text file then read the text file read the encrypted string decrypt it in python

1 Answers1