python decode fernet key

Question

I have generated few fernet keys and stored in str format for reference. Now, I need to encode these fernet keys in str format to 32 url-safe base64-encoded bytes to decrypt my data.

from cryptography.fernet import Fernet as frt
keys=set()
keybin='keys'
keybin=open(keybin,'w')

for i in range(r.randint(5,14)):
 key=frt.generate_key()
 keys.add(key.decode())

for k in keys:
 keybin.write(str(k))
 keybin.write('\n')

I'm using below code to access the file and decrypt s

 key=linecache.getline(cfile,x).encode()
 key=base64.b64encode(key)
 print(key)
 f=frt(key)
 token =f.decrypt(s.encode())

But is giving me the below error:

    "Fernet key must be 32 url-safe base64-encoded bytes."
ValueError: Fernet key must be 32 url-safe base64-encoded bytes.

Answer 1

Try your code without base64 encoding your key ie:

from cryptography.fernet import Fernet as frt

key=frt.generate_key()
s = "message"
print('input string: {0}'.format(s))
#key=base64.b64encode(key) #no need to do this
print('key: {0}, type: {1}'.format(key, type(key)))
f=frt(key)
token = f.encrypt(s.encode('utf-8')) #need to convert the string to bytes
print ('encrypted: {0}'.format(token))
output = f.decrypt(token)
output_decoded = output.decode('utf-8')
print ('decrypted: {0}'.format(output_decoded))