public Vote(int bh, Signature sig)
 {
     blockHash = bh;
     signature = new Signature(sig);
 }
 public Proposal(Block b, Signature sig)
 {
     block     = new Block(b.GetHash());
     signature = new Signature(sig);
 }
 /// Default constructor without any parameter must be implemented
 public Vote()
 {
     blockHash = -1;
     signature = new Signature();
 }
 /// Default constructor without any parameter must be implemented
 public Proposal()
 {
     block     = new Block();
     signature = new Signature();
 }