code: func KeysEqual(ak, bk PublicKey) bool {
  
  	//avoid panic if one of the keys is nil, return false instead
  	if ak == nil || bk == nil {
  		return false
  	}
  
  	a := ak.Marshal()
  	b := bk.Marshal()
  	return (len(a) == len(b) && subtle.ConstantTimeCompare(a, b) == 1)
  }
docs: // KeysEqual is constant time compare of the keys to avoid timing attacks.