```
import base64

fp = open("z","r").read()

base64_message = fp

while True:
base64_byte = base64_message[::-1]
base64_bytes = base64_byte.encode('ascii')
message_bytes = base64.b64decode(base64_bytes)
base64_message = message_bytes.decode('ascii')
if "CTF" in base64_message:
print base64_message
break
```

Original writeup (https://github.com/dianguc38/CTF/blob/master/affine/stego/revend64.py).