Simplified DES 키없이 복호화 코드

코드 (python)

EP = [4,1,2,3,2,3,4,1]
S0 = [[1,0,3,2],[3,2,1,0],[0,2,1,3],[3,1,3,2]]
S1 = [[0,1,2,3],[2,0,1,3],[3,0,1,0],[2,1,0,3]]
P4 = [2,4,3,1]
P10 = [3, 5, 2, 7, 4, 10, 1, 9, 8, 6]
P8 = [6, 3, 7, 4, 8, 5, 10, 9]
IP_1 = [4,1,3,5,7,2,8,6]
IP = [2, 6, 3, 1, 4, 8, 5, 7]

def shift_left(n, d, length):
    result = ((n<<d) & (2**length -1)) | (n>>(length - d))
    return result

def key_generator(key):
    #P10(key)
    p10 = [0] * len(P10)
    n = 0
    for i in P10:
        p10[n] = key[i-1]
        n+=1 
    p10_key = ''.join(p10)
    
    #key1 = P8(LS-1(P10(key)))
    c1 = p10_key[:5]
    d1 = p10_key[5:]
    
    #leftshift
    ls1_c = bin(shift_left(int(c1,2), 1, len(c1)))[2:].zfill(5)
    ls1_d = bin(shift_left(int(d1,2), 1, len(d1)))[2:].zfill(5)
    ls1_key = ls1_c + ls1_d
    
    #P8, Key1 generator
    p8 = [0] * len(P8)
    n = 0
    for i in P8:
        p8[n] = ls1_key[i-1]
        n+=1
    key1 = ''.join(p8)
    
    ls2_c = bin(shift_left(int(ls1_c,2), 2, len(ls1_c)))[2:].zfill(5)
    ls2_d = bin(shift_left(int(ls1_d,2), 2, len(ls1_d)))[2:].zfill(5)
    ls2_key = ls2_c + ls2_d
    
    p8 = [0] * len(P8)
    n = 0
    for i in P8:
        p8[n] = ls2_key[i-1]
        n+=1
    key2 = ''.join(p8)
    
    return [key1, key2]
    
def decryption(cipher, key1, key2):
    
    #IP(cipher)
    ip_list = [0]*len(IP)
    n=0
    for i in IP:
        ip_list[n] = cipher[i-1]
        n+=1
    ip = ''.join(ip_list)

    l2 = ip[:4]
    r2 = ip[4:]
    #swap
    r1 = bin(int(l2,2) ^ int(func(r2,key2),2))[2:].zfill(4)
    l1 = r2
    r0 = r1
    l0 = bin(int(l1,2)^ int(func(r1,key1),2))[2:].zfill(4)
    
    lr = l0+r0
    
    pt_list = [0]*len(IP_1)
    n=0
    for i in IP_1:
        pt_list[n] = lr[i-1]
        n+=1
    pt= ''.join(pt_list)
    
    return pt

def func(r, key):
    ep_text = [0]*len(EP)
    n=0
    for i in EP:
        ep_text[n] = r[i-1]
        n+=1
    ep_r= ''.join(ep_text)
    ep_r_key = bin(int(ep_r, 2) ^ int(key, 2))[2:].zfill(8)
    
    bit_array = []
    n=0
    for i in ep_r_key:
        bit_array.append(i)
        if(n==3):
            row = int("0b"+bit_array[0]+bit_array[3],2)
            col = int("0b"+bit_array[1]+bit_array[2],2)
            s_0 = bin(S0[row][col])[2:].zfill(2)
            bit_array = []
        if(n==7):
            row = int("0b"+bit_array[0]+bit_array[3],2)
            col = int("0b"+bit_array[1]+bit_array[2],2)
            s_1 = bin(S1[row][col])[2:].zfill(2)
        n+=1    
    s = s_0+s_1
    
    p4_list = [0]*len(P4)
    n=0
    for i in P4:
        p4_list[n] = s[i-1]
        n+=1
    p4 = ''.join(p4_list)
    
    return p4

c1 = "11001000010010011010011101111100000001001011000001010111010101110111110011011100"
c2 = "0000101000011001000010101011110001111100000010001101110001001001"
c3 = "0000010001111100101001111101110011111010101"
c4 = "10000010101110111110011001000010010011010011101111100111110101011110011001000"
cipher = c1+c2+c3+c4

for i in range(1024):
    pt_list = []
    cipher_list = []
    
    key = bin(i)[2:].zfill(10)
    [key1, key2] = key_generator(key)
    
    for j in cipher :
        cipher_list.append(j)
        if len(cipher_list) == 8 :
            cipher_text = ''.join(cipher_list)
            pt = decryption(cipher_text, key1, key2)
            cipher_list = []
            pt_a = int(pt,2)
            
            if(pt_a > 31 and  pt_a < 128 ) :
                pt_list.append(chr(pt_a))
            
    if(len(pt_list) > 32):
        print("key :: ("+str(bin(i)[2:])+")",str(i),"  /  PlainText :: ",''.join(pt_list))
   

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