On 03/13/2015 11:05 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 10:28 Fri 13 Mar     , Jan Lübbe wrote:
>> On Do, 2015-03-12 at 19:19 +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
>>> please do not send a new version except for fix
>>>
>>> I'm going to re-integrate it with the keystore & co
>>
>> Could you describe your keystore design?
> 
> I'll send the patch series soon
> 
> code is better than 1000s of words
> 
> with DER support and the fit
>>
>>> and sha1,rsa2048 is considered weak in term of security
>>> and worse md4/md5
>>>
>>> for barebox I would only use
>>> at least sha256 with rs2048 or sha512 with rsa4096
>>
>> Yes, of course. These were only used as an example and it's trivial to
>> switch to other hash algos or RSA key sizes. Also, the FIT format can
>> easily be extended to support ECC/Curve25519.
> 
> very slow vs rsa, but as we will use a generic framework we will just need to
> add the algo
> 
> if you can break rsa4096, the chance you can break ECC are high too

If you want to open the box, today you would probably not break
rsa2048/sha1 (unless you have huge calculation power) but look for
implementation weaknesses, like bugs or side channel attacks.

>> In some cases, where the SoC's ROM code only supports RSA2048 with SHA1,
>> using stronger settings in Barebox doesn't increase security. So there
>> we want to use the same settings as the ROM code.
> 
> agreed but I refuse to allow it unless we have no choice
> and emit a warning
> 
> and even I'll prefer to use stonger, yes this will increase the security.
> As a secure boot is as strong as it's weak link
> 
> but this will not reduce it either

Adding unneeded complexity might not the best move here.

Marc

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