SECCON 2017 Online CTF - Vigenere3d

vigenere3d.py

s = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz_{}"

#鍵を無理やり求めるやつ
def sa(s1,s2):
    c = []
    for i in range(7):
        i1 = s.find(s1[i])
        i2 = s.find(s2[i])
        c.append(i1-i2)
    return c

#換字暗号の解読
def dec(src,key):
    c=""
    keyall = key + key[::-1]
    for i in range(len(src)):
        c = c + s[(s.find(src[i]) + keyall[i%len(keyall)])%len(s)]
    return c


key = sa("SECCON{","POR4dny")
ans = dec("POR4dnyTLHBfwbxAAZhe}}ocZR3Cxcftw9", key)
print(ans)