SECCON 2016 Vegenere(Crypt 100)

vegenere_dec.py

# encoding: utf-8
import hashlib

table = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ{}'
tableNum = len(table)

ansHash = 'f528a6ab914c1ecf856a1d93103948fe'

p1 = 'SECCON{A'
c2 = 'DOEE'
p3 = 'BCDEDEFG'
c4 = 'JWMN'
p5 = 'KLMNOPQR'
c6 = 'UFWY'
p7 = 'VWXYYZ}'
flag = False

def p_search(c, k):
  k_num = table.find(k)
  for i in xrange(tableNum):
    if c == table[(i+k_num) % tableNum]:
      p = table[i]
      break
  return p

for j in xrange(tableNum):
  p2_1 = p_search(c2[0], table[j])
  p4_1 = p_search(c4[0], table[j])
  p6_1 = p_search(c6[0], table[j])
  for k in xrange(tableNum):
    p2_2 = p_search(c2[1], table[k])
    p4_2 = p_search(c4[1], table[k])
    p6_2 = p_search(c6[1], table[k])
    for l in xrange(tableNum):
      p2_3 = p_search(c2[2], table[l])
      p4_3 = p_search(c4[2], table[l])
      p6_3 = p_search(c6[2], table[l])
      for m in xrange(tableNum):
        p2 = p2_1 + p2_2 + p2_3 + p_search(c2[3], table[m])
        p4 = p4_1 + p4_2 + p4_3 + p_search(c4[3], table[m])
        p6 = p6_1 + p6_2 + p6_3 + p_search(c6[3], table[m])
        
        flag = p1 + p2 + p3 + p4 + p5 + p6 + p7
        flagMD5 = hashlib.md5(flag).hexdigest()
        if flagMD5 == ansHash:
          print flag
          exit(0)