python實現DES加密
阿新 • • 發佈：2020-07-14
加密流程
首先說一下置換的意思，比如說有5678這個字串，置換表為2143，置換表中的數表示的是位置，所以字串變成6587。所有的置換表在程式中。（S盒置換不一樣，會另外說明）
金鑰部分
- 把8位字串金鑰變成2進位制（好像金鑰只可以是8位，這一塊我也沒有搞太清楚）
- 64位金鑰進行PC1置換，變成56位，因為以前DES是用硬體實現的，所以8，16，24，32，40，48，56，64位為校驗位，不記入金鑰部分。但是我們現在是用軟體實現，所以這8位需要去掉，再打亂順序。
- 將56位金鑰對半分L0和R0、分別對L0和R0進行左迴圈移位，（當輪數為第1、2、9、16輪時，移動1位，其餘時候移動兩位）L0,R0移動1位後得到L1，R1。L1和R0繼續進行下一輪，進行16輪。
- 上面移位得到的所以Li+Ri進行PC2置換得到16個子金鑰（PC2置換把56位資料變成了48位）。
明文部分
- 先進行明文填充，採用PKCS #5規則，如果剛好滿足每組有8個位元組，則再新增一組，每個位元組為000010000，如果最後一組沒有8個位元組，則把這一組填充成8個位元組，填充的位元組為少掉的位元組的數目，比如有7個位元組，則填充00000001。
- 再進行初始置換，把64位明文打亂。
- 進行16輪feistel函式後在進行逆初始運算
feistel函式
以一組為例子來說明，一組明文8個位元組，64位。有16輪迭代，要執行16次feistel函式。注意在16輪迭代前要把明文進行初始置換，迭代後把左右兩邊資料合併成64位再進行逆初始運算
-
把64位明文左右對半分成兩份。
-
右邊的先進行部分進行擴充套件置換，32位變成48位。
-
再和對應輪數的子金鑰進行異或運算。
-
再進行S盒運算，48位變成32位。S盒運算具體操作方法是，把48位資料分成8份，每份就有6位資料，比如010110，把頭和尾結合位00，變成十進位制就是0，中間四位的十進位制為11，所以(x,y)為（0,11）
[14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7, 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8, 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0, 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13]在上面這個表中表示的就是12，在把12變成2進位制就是1100，所以6位就變成了4位。總共有8份資料，也有8個表。每份對應的運算的表都不一樣。
-
再進行P盒運算。
-
最後和左邊的32位進行異或運算。
解密
解密部分除了在feistel函式中呼叫子金鑰的順序相反外，其他都一樣。加密呼叫的順序是1-16，解密是16-1。
程式碼
#################################輔助函式######################################
# 十進位制轉成二進位制
def INT_BIN(NUM):
i = bin(NUM)[2:]
if len(i) != 8:
i = ((8 - len(i)) * '0') + i
return i
# 置換函式
def Replace(ARR,change):
ARR1 = []
for i in ARR:
a = ''
for j in change:
a += i[j-1]
ARR1.append(a)
return ARR1
# 異或運算
def XOR(a,b):
c=""
for i,j in zip(a,b):
if i==j:
c+='0'
else:
c+='1'
return [c]
# 二進位制轉字元
def ASCII(A):
text = ''
for i in A:
for j in range(8):
b = i[j*8:(j+1)*8]
text += chr(int(b,2))
return text
##############################################################################
#################################金鑰生成######################################
# 先PC1置換、將56位金鑰對半分L0和R0、分別對L0和R0進行左迴圈移位，
# （當輪數為第1、2、9、16輪時，移動1位，其餘時候移動兩位）L0,R0移動1位
# 後得到L1，R1，L1+R0進行PC2置換得到金鑰K1，L1和R0繼續進行下一輪，直到生成16個子金鑰
# PC-1置換表
PC1 = [57, 49, 41, 33, 25, 17, 9,
1, 58, 50, 42, 34, 26, 18,
10, 2, 59, 51, 43, 35, 27,
19, 11, 3, 60, 52, 44, 36,
63, 55, 47, 39, 31, 23, 15,
7, 62, 54, 46, 38, 30, 22,
14, 6, 61, 53, 45, 37, 29,
21, 13, 5, 28, 20, 12, 4]
# PC-2置換表
PC2 = [14, 17, 11, 24, 1, 5,
3, 28, 15, 6, 21, 10,
23, 19, 12, 4, 26, 8,
16, 7, 27, 20, 13, 2,
41, 52, 31, 37, 47, 55,
30, 40, 51, 45, 33, 48,
44, 49, 39, 56, 34, 53,
46, 42, 50, 36, 29, 32]
# 生成子金鑰函式
def GenerateSubkey(Key):
# 字串轉二進位制
K = ""
i_byte = bytes(Key, encoding='utf-8')
for i_bin in i_byte:
K += INT_BIN(i_bin)
# PC1置換
ReplacePc1 = Replace([K],PC1)
# 生成16組子金鑰
Lmi = []
Rmi = []
Lmi.append(ReplacePc1[0][:28])
Rmi.append(ReplacePc1[0][28:])
for i in range(1,17):
if i in (1, 2, 9, 16):
Lmi.append(Lmi[i-1][1:]+Lmi[i-1][:1])
Rmi.append(Rmi[i-1][1:]+Rmi[i-1][:1])
else:
Lmi.append(Lmi[i-1][2:]+Lmi[i-1][:2])
Rmi.append(Rmi[i-1][2:]+Rmi[i-1][:2])
del Lmi[0]
del Rmi[0]
del ReplacePc1[0]
for i in range(16):
ReplacePc1.append(Lmi[i]+Rmi[i])
# PC2置換
return Replace(ReplacePc1,PC2)
###########################################################################
#################################明文處理###################################
# 明文填充，採用PKCS #5規則，如果剛好滿足每組有8個位元組，則再新增一組，每個位元組為
# 000010000，如果最後一組沒有8個位元組，則把這一組填充成8個位元組，填充的位元組為少掉的
# 位元組的數目，比如有7個位元組，則填充00000001
# 對明文進行填充，分組
def InitPlaintext(Plaintext):
DecimalList = []
BytesList = []
BinList = []
# 字串轉成10機制
i_byte = bytes(Plaintext, encoding='utf-8')
for i_bin in i_byte:
DecimalList.append(i_bin)
# 剛好滿足分組
if len(DecimalList) % 8 == 0:
for i in range(8):
DecimalList.append(8)
for i in range(int(len(DecimalList)/8)):
BytesList.append(DecimalList[i*8:(i+1)*8])
# 不滿足分組
else:
INT = 8 - len(DecimalList) % 8
for i in range(INT):
DecimalList.append(INT)
for i in range(int(len(DecimalList)/8)):
BytesList.append(DecimalList[i*8:(i+1)*8])
# 10進位制轉2進位制
for i in BytesList:
TMP = ''
for j in i:
TMP += INT_BIN(j)
BinList.append(TMP)
return BinList
###########################################################################
################################feistel函式################################
#ip初始置換表
IPINIT = [58, 50, 42, 34, 26, 18, 10, 2,
60, 52, 44, 36, 28, 20, 12, 4,
62, 54, 46, 38, 30, 22, 14, 6,
64, 56, 48, 40, 32, 24, 16, 8,
57, 49, 41, 33, 25, 17, 9, 1,
59, 51, 43, 35, 27, 19, 11, 3,
61, 53, 45, 37, 29, 21, 13, 5,
63, 55, 47, 39, 31, 23, 15, 7]
#擴充套件E置換表
EExten = [32, 1, 2, 3, 4, 5,
4, 5, 6, 7, 8, 9,
8, 9, 10, 11, 12, 13,
12, 13, 14, 15, 16, 17,
16, 17, 18, 19, 20, 21,
20, 21, 22, 23, 24, 25,
24, 25, 26, 27, 28, 29,
28, 29, 30, 31, 32, 1]
#P盒置換表
PBOX = [16, 7, 20, 21,
29, 12, 28, 17,
1, 15, 23, 26,
5, 18, 31, 10,
2, 8, 24, 14,
32, 27, 3, 9,
19, 13, 30, 6,
22, 11, 4, 25]
#逆初始置換表
P1 = [40, 8, 48, 16, 56, 24, 64, 32,
39, 7, 47, 15, 55, 23, 63, 31,
38, 6, 46, 14, 54, 22, 62, 30,
37, 5, 45, 13, 53, 21, 61, 29,
36, 4, 44, 12, 52, 20, 60, 28,
35, 3, 43, 11, 51, 19, 59, 27,
34, 2, 42, 10, 50, 18, 58, 26,
33, 1, 41, 9, 49, 17, 57, 25]
#8個s盒
S_1 = [14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13]
S_2 = [15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9]
S_3 = [10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12]
S_4 = [7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14]
S_5 = [2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3]
S_6 = [12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13]
S_7 = [4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12]
S_8 = [13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11]
S_9 = []
S_9.append(S_1)
S_9.append(S_2)
S_9.append(S_3)
S_9.append(S_4)
S_9.append(S_5)
S_9.append(S_6)
S_9.append(S_7)
S_9.append(S_8)
# S盒置換
def S(R):
s = ''
for i in range(8):
a = R[i*6:(i+1)*6]
x = int(a[0]+a[-1],2)
y = int(a[1:5],2)
s += INT_BIN(S_9[i][x*15+y])[4:]
return[s]
# feistel函式
def feistel(L, R, K):
# 擴充套件置換
Expand = Replace(R,EExten)
# 異或運算
Expand = XOR(Expand[0],K)
# S盒運算
Expand = S(Expand[0])
# P盒
Expand = Replace(Expand,PBOX)
# 異或運算
Expand = XOR(L[0],Expand[0])
return Expand[0]
###########################################################################
################################加、解密函式################################
# 加密
def Encrypt(PlanText,Key):
# 初始置換
IP1 = Replace(InitPlaintext(PlanText),IPINIT)
# 生成子金鑰
SubkeyList = GenerateSubkey(Key)
# 16輪迭代
Ciphertext = []
for i in IP1:
L = i[:32]
R = i[32:]
for k in SubkeyList:
TMP = feistel([L],[R],k)
L = R
R = TMP
# 逆初始置換
Ciphertext.append(Replace([R+L],P1)[0])
return Ciphertext,SubkeyList
# 解密
def Decrypt(Ciphertext,Key):
# 初始置換
IP1 = Replace(Ciphertext,IPINIT)
# 16輪迭代
PlanText = []
for i in IP1:
L = i[:32]
R = i[32:]
for k in Key[::-1]:
TMP = feistel([L],[R],k)
L = R
R = TMP
# 逆初始置換
PlanText.append(Replace([R+L],P1)[0])
return PlanText
###########################################################################
if __name__ == "__main__":
miwen,miyao = Encrypt('computer','networks')
print(miwen)
print(ASCII(Decrypt(miwen,miyao)))