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BQ20Z65 SHA-1 feature: what happens if someone tries to break in?

Bernhard Krämer
Prodigy 20 points
Other Parts Discussed in Thread: BQ20Z65, BQ20Z65-R1, BQ20Z60-R1

I am constructing a battery that I'd like to protect using BQ20Z65's built-in SHA-1 encryption.

The question is: When someone wants to find out the right key in order to gain full access over the BQ20Z65, he would probably try out a lot of different keys. What happens if he enters a couple of wrong keys in a row? Will there be a certain time out until he can try again? I like to find out the probability that someone makes it to crack both 32 bit keys.

  • 0
    Intellectual 290 points

    Hi Bernhard

     

    See on page 65 of the Tech Ref,

    A.1.2.14 Unseal Device (UnsealKey)

    Instructs the bq20z60-R1/bq20z65-R1 to enable access to the SBS functions and data flash space and

    clear the [SS] flag. This two-step command must be written to ManufacturerAccess in the following order:

    first word of the UnSealKey first, followed by the second word of the UnSealKey. If the command fails, 4

    seconds must pass before the command can be reissued. This command is only available when the bq20z60-R1/bq20z65-R1 is in Sealed mode.

     

    So I think it's not impossible that someone could (e.g. a battery counterfeiter) hack the password for the Unsealed mode, but unlikely as also when hacking 100 battery packs in parallel it would need a lot of time. 

     

    All the best,

     

    Patrick

  • 0
    TI__Prodigy 515 points

    Hi Bernhard,

    The bq20z65 will force a 4-second timeout between access attempts. Also, just a clarification, the unseal and full access security modes are each protected by a 32-bit key but the SHA-1 authentication function uses a 16-byte key. Authentication is the host checking the identity of the pack. Unseal and Full Access are the pack checking the identity of the host.