76 lines
1.8 KiB
Python
76 lines
1.8 KiB
Python
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from struct import pack, unpack
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import ucryptolib
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MODE_ECB = 1
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class AES_CMAC:
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def gen_subkey(self, K):
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AES_128 = ucryptolib.aes(bytearray(K), MODE_ECB)
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L = AES_128.encrypt(('\x00'*16).encode())
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LHigh = unpack('>Q',L[:8])[0]
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LLow = unpack('>Q',L[8:])[0]
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K1High = ((LHigh << 1) | ( LLow >> 63 )) & 0xFFFFFFFFFFFFFFFF
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K1Low = (LLow << 1) & 0xFFFFFFFFFFFFFFFF
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if (LHigh >> 63):
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K1Low ^= 0x87
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K2High = ((K1High << 1) | (K1Low >> 63)) & 0xFFFFFFFFFFFFFFFF
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K2Low = ((K1Low << 1)) & 0xFFFFFFFFFFFFFFFF
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if (K1High >> 63):
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K2Low ^= 0x87
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K1 = pack('>QQ', K1High, K1Low)
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K2 = pack('>QQ', K2High, K2Low)
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return K1, K2
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def xor_128(self, N1, N2):
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J = b''
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for i in range(len(N1)):
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J += bytes([N1[i] ^ N2[i]])
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return J
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def pad(self, N):
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const_Bsize = 16
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padLen = 16-len(N)
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return N + b'\x80' + b'\x00'*(padLen-1)
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def encode(self, K, M):
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const_Bsize = 16
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const_Zero = b'\x00'*16
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AES_128 = ucryptolib.aes(bytearray(K), MODE_ECB)
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K1, K2 = self.gen_subkey(K)
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n = int(len(M)/const_Bsize)
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if n == 0:
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n = 1
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flag = False
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else:
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if (len(M) % const_Bsize) == 0:
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flag = True
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else:
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n += 1
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flag = False
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M_n = M[(n-1)*const_Bsize:]
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if flag is True:
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M_last = self.xor_128(M_n,K1)
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else:
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M_last = self.xor_128(self.pad(M_n),K2)
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X = const_Zero
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for i in range(n-1):
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M_i = M[(i)*const_Bsize:][:16]
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Y = self.xor_128(X, M_i)
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X = AES_128.encrypt(Y)
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Y = self.xor_128(M_last, X)
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T = AES_128.encrypt(Y)
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return T
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