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aes_decryption.py
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aes_decryption.py
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# -*- coding: utf-8 -*-
"""
Created on Thu Feb 11 10:02:40 2021
@author: Hari Sanjay
"""
def xor_bin(a,b):
t=""
for i in range(len(a)):
t=t+str(int(a[i])^int(b[i]))
return (bin_to_hexa(t)).upper()
def bin_to_hexa(s):
t=str(hex(int(s,2)))[2:]
t=((32-len(t))*'0')+t
return t
def sbox_value(s):
a=[]
sbox=['63', '7C', '77', '7B', 'F2', '6B', '6F', 'C5', '30', '01', '67', '2B', 'FE', 'D7', 'AB',
'76', 'CA', '82', 'C9', '7D', 'FA', '59', '47', 'F0', 'AD', 'D4', 'A2', 'AF', '9C', 'A4',
'72', 'C0', 'B7', 'FD', '93', '26', '36', '3F', 'F7', 'CC', '34', 'A5', 'E5', 'F1', '71',
'D8', '31', '15', '04', 'C7', '23', 'C3', '18', '96', '05', '9A', '07', '12', '80', 'E2',
'EB', '27', 'B2', '75', '09', '83', '2C', '1A', '1B', '6E', '5A', 'A0', '52', '3B', 'D6',
'B3', '29', 'E3', '2F', '84', '53', 'D1', '00', 'ED', '20', 'FC', 'B1', '5B', '6A', 'CB',
'BE', '39', '4A', '4C', '58', 'CF', 'D0', 'EF', 'AA', 'FB', '43', '4D', '33', '85', '45',
'F9', '02', '7F', '50', '3C', '9F', 'A8', '51', 'A3', '40', '8F', '92', '9D', '38', 'F5',
'BC', 'B6', 'DA', '21', '10', 'FF', 'F3', 'D2', 'CD', '0C', '13', 'EC', '5F', '97', '44',
'17', 'C4', 'A7', '7E', '3D', '64', '5D', '19', '73', '60', '81', '4F', 'DC', '22', '2A',
'90', '88', '46', 'EE', 'B8', '14', 'DE', '5E', '0B', 'DB', 'E0', '32', '3A', '0A', '49',
'06', '24', '5C', 'C2', 'D3', 'AC', '62', '91', '95', 'E4', '79', 'E7', 'C8', '37', '6D',
'8D', 'D5', '4E', 'A9', '6C', '56', 'F4', 'EA', '65', '7A', 'AE', '08', 'BA', '78', '25',
'2E', '1C', 'A6', 'B4', 'C6', 'E8', 'DD', '74', '1F', '4B', 'BD', '8B', '8A', '70', '3E',
'B5', '66', '48', '03', 'F6', '0E', '61', '35', '57', 'B9', '86', 'C1', '1D', '9E', 'E1',
'F8', '98', '11', '69', 'D9', '8E', '94', '9B', '1E', '87', 'E9', 'CE', '55', '28', 'DF',
'8C', 'A1', '89', '0D', 'BF', 'E6', '42', '68', '41', '99', '2D', '0F', 'B0', '54', 'BB', '16']
t=""
for i in range(0,len(s),2):
temp=s[i:i+2]
if(temp[0].isalpha()):
sbox_row=ord(temp[0])-55
else:
sbox_row=int(temp[0])
if(temp[1].isalpha()):
sbox_column=ord(temp[1])-55
else:
sbox_column=int(temp[1])
t=sbox[(sbox_row*16)+sbox_column]
a.append(t)
X=[]
for i in range(0,len(a),4):
X.append(a[i:i+4])
result = [[X[j][i] for j in range(len(X))] for i in range(len(X[0]))]
return result
#convert 32 hexa to 128 binary
def hexa_to_bin(s):
t=""
for i in s:
a=format(int(i,16), '0>42b')
t=t+a[-4:]
return t
def generate_keys(hexa_key):
words=[]
rconst=["01000000", "02000000", "04000000", "08000000", "10000000", "20000000",
"40000000", "80000000", "1B000000", "36000000", "6C000000", "D8000000",
"AB000000", "4D000000"]
for i in range (0,len(hexa_key),8):
words.append(hexa_key[i:i+8])
ite=0
if(len(hexa_key)==32):
ite=11
elif(len(hexa_key)==48):
ite=13
elif(len(hexa_key)==64):
ite=15
for i in range(1,ite):
temp=words[(i*4)-1]
temp=temp[2:]+temp[:2]
temp=sbox_value(temp)
temp1=""
for j in temp:
for k in j:
temp1+=k
temp=temp1
temp=xor_bin(hexa_to_bin(temp),hexa_to_bin(rconst[i-1]))
temp=temp[-8:]
for j in range(4):
w=(i*4)+j
if(w%4==0):
ttttt=xor_bin(hexa_to_bin(temp),hexa_to_bin(words[w-4]))
words.append(ttttt[-8:])
else:
ttttt=xor_bin(hexa_to_bin(words[w-1]),hexa_to_bin(words[w-4]))
words.append(ttttt[-8:])
keysss=[]
for i in range(0,len(words),4):
sample=""
for j in range(4):
sample=sample+words[i+j]
keysss.append(sample)
return keysss
def bitwise_multiplication(a,b):
fx=[]
gx=[]
f=hexa_to_bin(a)[::-1]
g=hexa_to_bin(b)[::-1]
m="00011011"
for i in range(len(f)):
if(f[i]=='1'):
fx.append(i)
if(g[i]=='1'):
gx.append(i)
fx=fx[::-1]
gx=gx[::-1]
f=f[::-1]
g=g[::-1]
mx=[]
mx.append(g)
for i in range(1,fx[0]+1):
shiftmx=mx[i-1][1:]+'0'
if(mx[i-1][0]=="1"):
shiftmx=xor_bin(shiftmx,m)
shiftmx=hexa_to_bin(shiftmx)[-8:]
mx.append(shiftmx)
result="00000000"
for i in fx:
result=xor_bin(result,mx[i])
result=hexa_to_bin(result)[-8:]
return result
def inverse_sbox(s):
sbox=['52', '09', '6A', 'D5', '30', '36', 'A5', '38', 'BF', '40', 'A3', '9E', '81', 'F3', 'D7', 'FB',
'7C', 'E3', '39', '82', '9B', '2F', 'FF', '87', '34', '8E', '43', '44', 'C4', 'DE', 'E9', 'CB',
'54', '7B', '94', '32', 'A6', 'C2', '23', '3D', 'EE', '4C', '95', '0B', '42', 'FA', 'C3', '4E',
'08', '2E', 'A1', '66', '28', 'D9', '24', 'B2', '76', '5B', 'A2', '49', '6D', '8B', 'D1', '25',
'72', 'F8', 'F6', '64', '86', '68', '98', '16', 'D4', 'A4', '5C', 'CC', '5D', '65', 'B6', '92',
'6C', '70', '48', '50', 'FD', 'ED', 'B9', 'DA', '5E', '15', '46', '57', 'A7', '8D', '9D', '84',
'90', 'D8', 'AB', '00', '8C', 'BC', 'D3', '0A', 'F7', 'E4', '58', '05', 'B8', 'B3', '45', '06',
'D0', '2C', '1E', '8F', 'CA', '3F', '0F', '02', 'C1', 'AF', 'BD', '03', '01', '13', '8A', '6B',
'3A', '91', '11', '41', '4F', '67', 'DC', 'EA', '97', 'F2', 'CF', 'CE', 'F0', 'B4', 'E6', '73',
'96', 'AC', '74', '22', 'E7', 'AD', '35', '85', 'E2', 'F9', '37', 'E8', '1C', '75', 'DF', '6E',
'47', 'F1', '1A', '71', '1D', '29', 'C5', '89', '6F', 'B7', '62', '0E', 'AA', '18', 'BE', '1B',
'FC', '56', '3E', '4B', 'C6', 'D2', '79', '20', '9A', 'DB', 'C0', 'FE', '78', 'CD', '5A', 'F4',
'1F', 'DD', 'A8', '33', '88', '07', 'C7', '31', 'B1', '12', '10', '59', '27', '80', 'EC', '5F',
'60', '51', '7F', 'A9', '19', 'B5', '4A', '0D', '2D', 'E5', '7A', '9F', '93', 'C9', '9C', 'EF',
'A0', 'E0', '3B', '4D', 'AE', '2A', 'F5', 'B0', 'C8', 'EB', 'BB', '3C', '83', '53', '99', '61',
'17', '2B', '04', '7E', 'BA', '77', 'D6', '26', 'E1', '69', '14', '63', '55', '21', '0C', '7D']
a=[]
for i in range(0,len(s),2):
temp=s[i:i+2]
if(temp[0].isalpha()):
sbox_row=ord(temp[0])-55
else:
sbox_row=int(temp[0])
if(temp[1].isalpha()):
sbox_column=ord(temp[1])-55
else:
sbox_column=int(temp[1])
t=sbox[(sbox_row*16)+sbox_column]
a.append(t)
X=[]
for i in range(0,len(a),4):
X.append(a[i:i+4])
result = [[X[j][i] for j in range(len(X))] for i in range(len(X[0]))]
return result
def inverse_shift(s):
t=[]
t.append(s[0])
for i in range(1,len(s)):
temp=s[i]
temp=temp[-1*i:]+temp[:-1*i]
t.append(temp)
return t
def inverse_mixcolumn(Y):
X=[['0E','0B','0D','09'],
['09','0E','0B','0D'],
['0D','09','0E','0B'],
['0B','0D','09','0E']]
result=[]
for i in range(len(X)):
tt=[]
for j in range(len(Y[0])):
r="00000000"
for k in range(len(Y)):
t=bitwise_multiplication(X[i][k],Y[k][j])
r = xor_bin(r,t)
r = hexa_to_bin(r)[-8:]
tt.append(bin_to_hexa(r)[-2:].upper())
result.append(tt)
return result
def array_to_str(s):
mixcolumn=""
for j in s:
for k in j:
mixcolumn+=k
return mixcolumn
def str_to_array(a):
X=[]
j=1
Y=[]
for i in range(0,len(a),2):
Y.append(a[i:i+2])
if(j%4==0):
X.append(Y)
Y=[]
j+=1
return X
def eight(s):
c=1
m=[]
t=[]
for i in range(0,len(s),2):
t.append(s[i]+s[i+1])
s=t
t=[]
for i in s:
t.append(i)
if(c%4==0):
m.append(t)
t=[]
c=c+1
return m
def decrypt(hexa_key,plaintext):
keys=generate_keys(hexa_key)
keys=keys[::-1]
pre=xor_bin(hexa_to_bin(plaintext) , hexa_to_bin(keys[0]))
pre=str_to_array (pre)
X=pre
pre=[[X[j][i] for j in range(len(X))] for i in range(len(X[0]))]
pre=inverse_shift(pre)
pre=array_to_str(pre)
pre=inverse_sbox(pre)
pre=array_to_str(pre)
for i in range(1,len(keys)-1):
pre=xor_bin(hexa_to_bin(pre) , hexa_to_bin(keys[i]) )
X=pre=str_to_array (pre)
pre=[[X[j][i] for j in range(len(X))] for i in range(len(X[0]))]
X=pre=inverse_mixcolumn (pre)
X=pre=inverse_shift(pre)
pre=array_to_str(pre)
pre=inverse_sbox(pre)
pre=array_to_str(pre)
print("Round:",i,"",pre)
pre=xor_bin(hexa_to_bin(pre),hexa_to_bin(hexa_key) )
print(pre,"\n")
return pre
def main():
hexa_key=input("Enter key")
#hexa_key="000102030405060708090a0b0c0d0e0f".upper()
lk=len(hexa_key)
if not(lk==32 or lk==48 or lk==64):
print("Key should a hex of size 32 or 48 or 64\n")
main()
plaintext=input("enter cipher text....")
#plaintext="69C4E0D86A7B0430D8CDB78070B4C55A69C4E0D86A7B0430D8CDB78070B4C55A"
lk=len(hexa_key)
lt=len(plaintext)
if not(lt%lk==0):
print("Invalid size\n")
main()
ite=int(lt/lk)
a=""
for i in range(ite):
text=plaintext[lk*i : lk*(i+1)]
v=decrypt(hexa_key,text)
a=a+v
print(a)
if __name__ == "__main__":
main()