code: func (s *Signatory) verifySignature(block *clearsign.Block) (*openpgp.Entity, error) {
  	return openpgp.CheckDetachedSignature(
  		s.KeyRing,
  		bytes.NewBuffer(block.Bytes),
  		block.ArmoredSignature.Body,
  	)
  }
docs: // verifySignature verifies that the given block is validly signed, and returns the signer.