Re: HELP writing crypto driver for HW with blocksize hash

On 11.07.2017 12:30, Gilad Ben-Yossef wrote:
> On Tue, Jul 11, 2017 at 10:52 AM, Kamil Konieczny
> <[email protected]> wrote:
>>
>>
>> I am writing crypto driver for hash MD5/SHA1/SHA256 on Exynos 4412,
>> and I am facing some (minor?) difficulties. [...]

>> So there is no [...] final method.
>>
>> It must be feeded with at least one message byte to produce hash.
>>
>> One more constrain is to process data in constant-sized chunks,
>> here it is 64 bytes, the same as for AES block,
>> i.e. it cannot stop and export state while in middle of block,
>> example - if we feed 16 bytes, we must then feed 48 bytes
>> to stop, but ideally we should feed it always 64 bytes. [...]
>>
>> Any suggestions ?
>>
>> Can i keep some bytes unfeeded from ahash_request
>> and return -EINPROGRESS ?
>> Should i set timer and copy rest bytes after some timeout,
>> where no more requests are incoming ? Or not ? cause it is
>> async mode ?
>> can i wait for more requests for processing waiting one ?
> Your two constraints are actually inter-related -
> 
> If you can only feed the HW a constant size chunk, than indeed need to
> keey bytes fed
> to the driver the are below the chunk size in a software buffer, but
> than you need the final()
> method to feed these bytes (padded as needed) to the HW if they are
> the last bytes
> 
> Gilad

HW will done padding

I want to avoid memcpy iff possible for async hash

-- 
Best regards,
Kamil Konieczny
Samsung R&D Institute Poland