Acquire Entropy for embedded platform

Dr Paul Dale paul.dale at
Fri Aug 16 09:33:11 UTC 2019

Two bits of RTC is nowhere near enough entropy.  I could break two bits by hand in a few seconds — there are only four possibilities.

The best outcome is an hardware random number generator.  These are often not readily available.

Next would be waiting for enough entropy from interrupts, timers and the like.

You didn’t specify what operating system/kernel you are using so further advise is less than useful.

Dr Paul Dale | Distinguished Architect | Cryptographic Foundations 
Phone +61 7 3031 7217
Oracle Australia

> On 16 Aug 2019, at 7:26 pm, Chitrang Srivastava <chitrang.srivastava at> wrote:
> Hi,
> I am working on an embedded platform and now ported openssl 1.1.1b
> TLS 1.2/1.3 is working fine.
> While analysing random number , Rand pool initialization calls where I am returning like this , 
> size_t rand_pool_acquire_entropy(RAND_POOL *pool)
> {
>         return rand_pool_entropy_available(pool);
> }  
> As noticed that rand_unix.c has an implementation wcih samples 2 bits of RTC, would that give enough entropy or any other recommendation to have enough entropy for embedded platforms?
> Thanks,

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