Using OP instead of OPC

[b3c3ll]

Hi
Thanks for your great repo!
I was wondering if it is possible to use OP instead of OP for AUC authentication?

Thanks
Best regards

[svinson1121]

I think PyHSS only supports OPC

you can calculate the OPC from the OP and KI (OPC = AES128(ki,OP) XOR OP)

I did something in python to do this:

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from Crypto.Cipher import AES
import binascii

def calculate_opc(ki, op):
# Convert the Ki and OP values from hex strings to byte arrays
ki_bytes = binascii.unhexlify(ki)
op_bytes = binascii.unhexlify(op)

# Create a new AES object with the Ki value as the key
aes = AES.new(ki_bytes, AES.MODE_ECB)

# Use the AES object to encrypt the OP value
encrypted_op = aes.encrypt(op_bytes)

# XOR the encrypted OP value with the original OP value to get the OPC value
opc = bytearray(len(op_bytes))
for i in range(len(op_bytes)):
    opc[i] = encrypted_op[i] ^ op_bytes[i]

# Convert the OPC value to a hex string and return it
return binascii.hexlify(opc).decode('utf-8')

ki = (input('Enter Ki: '))
op = (input('Enter Op: '))
opc = calculate_opc(ki, op)
print('OPc: ' + opc)