SHAlphabet

Flag: ECW{ringckouck}

Challenge

23KB

houko_SHAlphabet.zip

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Description

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We intercept a password database. But we still miss the admin password, we only have the corresponding hash ! Can you break it ?

The flag is in the format ECW{password}.

Challenge made by:

Solution

Dans le fichier database.txt, il fallait repérer que les mots étaient toujours formés des mêmes groupes de lettres :

ing    ck    sp    th
ly     r     ae    oa
eu     oo    uu    a
e      i     o     u

Il y a 16 possiblités, ce qui est assez faible, on peut donc bruteforce le SHA256 pour trouver le mot d'origine :

import hashlib
import itertools

SYLS = ["ing","ck","sp","th","ly","r","ae","oa","eu","oo","uu","a","e","i","o","u"]
TARGET = bytes.fromhex('3c33e4fcfc797901b77a41febb30d67be4b175bd32d5fd8cf4c03ff7ceb94ca5')

def sha256_hex(s: str) -> bytes:
    return hashlib.sha256(s.encode()).digest()
  
for L in range(1, 7):
  print(f"Trying: {L}")
  for candidate in itertools.product(SYLS, repeat=L):
      candidate = ''.join(candidate)
      if sha256_hex(candidate) == TARGET:
          FOUND = candidate
          print(f'FOUND: {FOUND}')
          break

Trying: 1
Trying: 2
Trying: 3
Trying: 4
Trying: 5
Trying: 6
FOUND: ringckouck