Luigi Auriemma

Hi,

I want to find the algorithm coded in one arm cpu.

I have:
- the mcu dump file that crypt datas,
- uncrypted texts, (hex: E503565758375A30474E334E3631534F)
- cypher texts, (hex: 20E2926EAE64205DF872C7514DA6F9BA)
- key (48 bit) (hex: 4119835C8464)

I know it is a symetric algorythm.
uncrypted text and cypher text always have the same length.

When I run signsrch on the bin file, i get:

offset num description [bits.endian.size]
--------------------------------------------
00026cc4 163 AES Rijndael Logtable [..256]
00026dc4 164 AES Rijndael Alogtable [..256]
00026ecc 165 AES Rijndael S / ARIA S1 [..256]
00026fec 166 AES Rijndael Si / ARIA X1 [..256]
00026fd3 1636 Noekeon Nessie round [..17]

- 5 signatures found in the file


Please can you help me to find the crypto algorythm.
When I try with rijndael, I don't find good value.

I don't know wich mode to use (CBC, ECB...),
I dont know iv (initialisation vector) and,
AES Rijndael normally use 256 bits heys isn't it ?

Thanks for your help.

regards,

Krafeus

aes needs a key of 128, 192 or 256 bits so if the algorithm is aes then the key is invalid.

ecb doesn't use ivec but the others do so there is an additional problem to add in case it's aes non-ecb

maybe it's a custom algorithm but in that case don't know where starting

Hi aluigi,

Thanks for your quick answer.

Regards,

Krafeus