We continue discussing the paper "Shielding applications from an untrusted cloud with Haven,” written by Andrew Baumann, Marcus Peinado, and Galen Hunt.  We discussed SGX optimizations that could be attempted in newer releases but were found in the study by the authors. We continue to review the SGX hardware notes in the paper. We reviewed shielded VMs. We were reviewing Hardware security modules (HSM) that isolate applications from an untrusted OS. Another thing that serves this purpose is Trusted Hardware  or Trusted Platform Modules(TPM). TPMs are hardware devices that are included in many PCs supporting a similar attestation mechanism to SGX. It builds a progressive chain of trust using progressive measurement of code during system boot, such as a bootloader, OS etc. Recent advances have enabled late launch and dynamic attestation of an isolated security kernel. What this does is that it reduces the platform's trusted computing base to just the late launched code which is a form of isolated execution. However unlike SGX, this has two drawbacks:
one it is vulnerable to relatively simple hardware attack including memory snooping and two it lacks support for efficient multiplexing of late launch environments.
#codingexercise
A singer performs for an audience on the stage. The crowd has to be made standing ovation with every audience member standing up and clapping their hands for her.
Initially, the entire audience is seated. Everyone in the audience has a shyness level. An audience member with shyness level Si will wait until at least Si other audience members have already stood up to clap, and if so, she will immediately stand up and clap. If Si = 0, then the audience member will always stand up and clap immediately, regardless of what anyone else does. For example, an audience member with Si = 2 will be seated at the beginning, but will stand up to clap later after she sees at least two other people standing and clapping.
If the shyness level of everyone in the audience is known, and additional friends of the singer can be invited to be in the audience, can it be ensured that everyone in the crowd stands up and claps in the end ? Each of these friends may have any shyness value. What is the minimum number of friends needed to be invited to guarantee a standing ovation?

int GetClappers(int N, List<int>S) 

{ 

int rem = 0; 

int cur = 0; 

for (int i = 0; i < N + 1; i++) 

{ 

   if ( i  > cur ) 

   { 

       rem += i - cur; 

       cur = i; 

   } 

   cur += S[i]; 

} 

return rem; 

}