Algorithm 1. Authentication process in joining private blockchain

Require:Utype

Ensure:pk, sk, Uid, permit

1: permit = false;

2: {pk, sk} ←KeyGenerator ();

3: IDu ←pk;

4: Utype ∈ {Requester, agent};

5: if IDu been cleared three times or Blockchain is full then

6:   return permit

7:  else if IDu ∈ Poolu then

8:    permit = true;

9:  else if Poolu ←Poolu ∪ {IDu} then

permit = true;

10: end if

11: return permit