message: take reference only here
diff: @@ -44,7 +44,7 @@ impl SlotId {
  impl SignedBlock {
  /// Create a new signed block.
  - pub fn new(block: Block, pkey: PrivateKey) -> Self {
  + pub fn new(block: Block, pkey: &PrivateKey) -> Self {
  use chain_core::property::Block;
  let block_id = block.id();
  SignedBlock {
  