Tags: reverse-engineering rot13
Rating:
# YayRev
## Task
Let’s brush up sum pythan skillz… (no flag wrapper)
File: yayrev.py
## Solution
This one is a bit harder to understand:
```python
proficuous =flag
saxicolous = [ord(excogitate) for excogitate in proficuous]
ebullient = (saxicolous[-5:]); import random
second = (saxicolous[:-5])
sesquipedalian = ''.join(map(chr,ebullient)) + ''.join(map(chr,second))
vravar = ''.join([chr(permutation.islower() and ((ord(permutation) - 84) % 26) + 97
or permutation.isupper() and ((ord(permutation) - 52) % 26) + 65
or ord(permutation))
for permutation in sesquipedalian])
auspicious = []
for luminescent in vravar:
auspicious.append(luminescent)
for cupidity in range(200):
second = []
superabundant=random.choice(auspicious)
print( "mac>>>[" + str(auspicious.index(superabundant)) + "] " + "== " + "\"" + superabundant + "\"" + " and")
```
1. The last 5 chars are moved to the start
2. Something happens
3. The joined chars are moved into a list
4. 200 Random values are chosen from that list and we get their index and value
The 200 outputs are given so lets clean that up with a regex and do a `sort -u`. We now have only 18 values.
We need to reverse step 2 now.
```python
for c in [
chr(c.islower() and ((ord(c) - 84) % 26) + 97
or c.isupper() and ((ord(c) - 52) % 26) + 65
or ord(c))
for c in flagSwapped]:
out.append(c)
```
At first I didn't realize this, but it's just ROT13. If it's not upper or lowercase we just take the char.
```python
>>> chr((ord("Z") - 52) % 26 + 65)
'M'
>>> chr((ord("A") - 52) % 26 + 65)
'N'
```
All we have to do now:
```python
import codecs
...
print(codecs.encode(''.join(crypt[5:]) + ''.join(crypt[:5])), 'rot_13')
```
`Wh0a_l3gEnD-PytHON`
