5차시

aLIST="abcdefghijklmnopqrstuvwxyz"

def c_enc(Msg, K):
  c=""
  for i in Msg:
    idx=aLIST.find(i) #알파벳->숫자
    idx=(idx+K)%26 #암호화
    c=c+aLIST[idx] #숫자->알파벳
  return c

def c_dec(C,K):
  p=""
  for i in C:
    idx=aLIST.find(i) #알파벳->숫자
    idx=(idx-K)%26
    p=p+aLIST[idx]
  return p

def v_dec(msg, k):
    p=""
    klen=len(k)
    kidx=[]
    for i in k:
        idx = aLIST.find(i)
        kidx.append(idx)

    cnt=0
    for i in msg:
        idx = aLIST.find(i)
        idx = (idx-kidx[cnt])%26
        p = p+(aLIST[idx])
        cnt = (cnt+1)%klen

    return p

ct = "aebcfwedmkpfwxpngkqlhjemwqkoxajxeqbcfshgwkouyw"
for i in range(0,26):
    for j in range(0,26):
        for k in range(0, 26):
            for l in range(0, 26):
                tmp =""
                tmp = tmp+aLIST[i]
                tmp = tmp+aLIST[j]
                tmp = tmp +aLIST[k]
                tmp = tmp+aLIST[l]
                pt = v_dec(ct, tmp)
                if pt[0]=="i" and pt[1]=="m" and pt[2]=="f":
                    print("keY:", tmp, "msg:", pt)