problem with the function _Crypt_DecryptFile ( $sSourceFile, $sDestinationFile, $vCryptKey, $iAlgID )

[mehdi350]

I have a problem with the function _Crypt_DecryptFile ( $sSourceFile, $sDestinationFile, $vCryptKey, $iAlgID )
I encrypt an Excel file with _Crypt_Encrypt with the algorithm $CALG_AES_256 and with $vCryptKey=123
but when I launched a brute force to decrypt this file unfortunately this function Returns True even if $vCryptKey is different from 123
For example this function returns true even if $vCryptKey= 27 and 143 and 067
are there any negative holes in this function
thank you

[jchd]

Cross-posting on both the French and English fora is pointless. You've read my answer over there, so don't do it.

[mehdi350]

excuse me I posted this problem on the French and English forums to have different solutions

[Musashi]

2 hours ago, mehdi350 said:

... excuse me I posted this problem on the French and English forums to have different solutions

@jchd has already explained in detail (French forum), why the function _Crypt_DecryptFile may return True even though an incorrect CryptKey has been passed. However, in none of these cases does this function return the original file, meaning the operation is safe.  For interested users : Here is the 'french' link :  https://www.autoitscript.fr/forum/viewtopic.php?f=3&t=15803

So if you are looking for an alternative solution, then I recommend taking a look at the UDF cryptong-udf-cryptography-api-next-gen made by @TheXman.

Additional info : A brute force operation on an AES256 encrypted file, unless the password was chosen super simple, could take some time (your lifetime for example ). The use of such a simple password is strongly discouraged.

Edited September 2, 2022 by Musashi
additional info

[mehdi350]

thank you Musashi