HSE IVT Auth_TAG

liyongfeng — Wed, 14 May 2025 07:17:09 GMT

I used an offline tool to calculate the IVT GMAC, but the result differs from HSE's. I want to know how to obtain the same result based on applicationDebugKeyPassword[16U] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f }？

Re: HSE IVT Auth_TAG

davidtosenovjan — Thu, 15 May 2025 13:58:43 GMT

Please provide further details about used example codes and mentioned tool. Thanks

Re: HSE IVT Auth_TAG

liyongfeng — Wed, 21 May 2025 13:38:00 GMT

applicationDebugKeyPassword=000102...0F;

How to calculate the red part below using an offline tool to obtain the blue part's GMAC?

A5 5A A5 5A 09 00 00 00 00 00 00 00 00 60 44 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
C0 40 40 00 00 00 00 00 00 00 00 00 00 00 00 00
FF FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 79 AB 16 44 70 B3 B6 3D 4E 35 70 C1
44 E3 5F FC 7B 5A 1A E4 55 B3 03 C8 87 FA 25 A4

if __name__ == '__main__':
    key = b'000102030405060708090A0B0C0D0E0F'
    iv = b'79AB164470B3B63D4E3570C1'
    data = b'A55AA55A090000000000000000604400\
00000000000000000000000000000000\
00000000000000000000000000000000\
C0404000000000000000000000000000\
FFFFFFFF000000000000000000000000\
00000000000000000000000000000000\
00000000000000000000000000000000\
00000000000000000000000000000000\
00000000000000000000000000000000\
00000000000000000000000000000000\
00000000000000000000000000000000\
00000000000000000000000000000000\
00000000000000000000000000000000\
00000000000000000000000000000000\
0000000079AB164470B3B63D4E3570C1'
    aesgcm = AESGCM(key)
    gmac = aesgcm.encrypt(iv, data, None)[-16:]  # Last 16 bytes are GMAC
print(gmac.hex())

output：d6a5196d7573dd9bd49e9fce08ebb73b
It is different from the 16-byte IVT.GMAC shown in the figure above.

Re: HSE IVT Auth_TAG

davidtosenovjan — Fri, 30 May 2025 07:09:03 GMT

COuld you clarify which HSE example code you are referring to? Or describe how you do it on MCU side?

Re: HSE IVT Auth_TAG

davidtosenovjan — Fri, 30 May 2025 14:23:43 GMT

Potentially the issue could be that you are using ASCII characters in Python script but HSE uses direct bin values i.e. HEX numbers

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