Re: Acquire Entropy for embedded platform

Robert Moskowitz <rgm@xxxxxxxxxxxxxxx> · Fri, 16 Aug 2019 08:22:17 -0400



    On 8/16/19 5:44 AM, Dr Paul Dale wrote:

    
      I investigated HAVEGE fairly deeply a couple of years ago.  I am
      completely in agreement with the basis of this source, however the
      sticking point was the “expansion” phase.  Essentially, every bit
      of entropy gathered is turned into (just under) thirty two bits of
      “entropy”.  This is logically and physically impossible.  As a
      source, it appears reasonable to the usual tests (i.e. dieharder),
      although TestU01 does pick up on it being less
      than ideal.
      

      I would, however, recommend Stephan Müller's CPU Jitter.  The gathering
        is well researched and performed, no hidden tricks are present
        and the bits produces are equiprobable.

      
    Thanks.  I will take a look at CPU Jitter.  Entropy can be an issue
    on some of my armv7 boards.  I run CentOS on them, so all I need to
    find are rpms for something to test it out...

    
          Pauli
          
            
                -- 

                  Dr Paul Dale | Distinguished Architect | Cryptographic
                  Foundations 

                  Phone +61 7 3031 7217

                  Oracle Australia
                

                On 16 Aug 2019, at 7:31 pm, Robert
                  Moskowitz <rgm@xxxxxxxxxxxxxxx>
                  wrote:
                

                    On 8/16/19 5:26 AM,
                      Chitrang Srivastava 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?

                        
                    Check out:    https://issihosts.com/haveged

                    
                    I talk about it here:    http://www.htt-consult.com/CentOS7-armv7.html#RANDOMNESS