ksnctf : #5 Onion #CTF

This is the note when I found out #5 Onion of ksnctf.

It seems to encode base64, and I decode it. But a strings that I could not understand was displayed.

Decode and decode and decode,,,, but A head of the strings was same.

I write a below script in python.

# -*- coding: utf-8 -*-

import base64
import sys

argvs = sys.argv

text1 = argvs[1]

for i in range(0,16):
    text1 = base64.b64decode( text1 )

print text1

When range(0,16), following strings was displayed.

begin 666 <data>
51DQ!1U]&94QG4#-3:4%797I74$AU

end

I input 51DQ!1U]&94QG4#-3:4%797I74$AU to the FLAG form but answer was wrong.

I google begin/end format.
It appear uuencode.

I write a code in python to decode it.

# -*- coding: utf-8 -*-

import uu

uu.decode("5.txt.uuencode", "5.txt")

FLAG was appeared in 5.txt.