The cipher was multiple b64 encodings.
Script for decoding:
```
f=open("cipher.txt").read()
while(True):
try:
f=f.decode('base64')
except:
print f
break

#flag{l00ks_l1ke_a_l0t_of_64s}
```

Original writeup (https://github.com/noob-aViral/redpwn_writeups/blob/master/b6464.py).