/**
         * Returns the algorithm end result as string, never {@code null}. After invoking this method, this instance should
         * be discarded and not reused. For new checksum calculation you have to get new instance.
         */
        @Nonnull
        String checksum();
    }

#### A "professional" attack { #a-professional-attack }

Of course, the attackers would not try all this by hand, they would write a program to do it, possibly with thousands or millions of tests per second. And they would get just one extra correct letter at a time.

But doing that, in some minutes or hours the attackers would have guessed the correct username and password, with the "help" of our application, just using the time taken to answer.

	m.mu.RUnlock()
	if ok {
		return b.updateCacheEntry(update)
	}

	// We should have either a trashed bucket or this
	return metacache{}, errVolumeNotFound
}

// getBucket will get a bucket metacache or load it from disk if needed.
func (m *metacacheManager) getBucket(ctx context.Context, bucket string) *bucketMetacache {
	m.init.Do(m.initManager)

		reqRecorder := &xhttp.RequestRecorder{Reader: r.Body}
		r.Body = reqRecorder

		// Create tracing data structure and associate it to the request context
		tc := mcontext.TraceCtxt{
			AmzReqID:         w.Header().Get(xhttp.AmzRequestID),
			RequestRecorder:  reqRecorder,
			ResponseRecorder: respRecorder,
		}

		r = r.WithContext(context.WithValue(r.Context(), mcontext.ContextTraceKey, &tc))

		reqStartTime := time.Now().UTC()

        return (CrawlingInfoParamCB) this;
    }

    @Override
    public void acceptPrimaryKeyMap(Map<String, ? extends Object> primaryKeyMap) {
        acceptPK((String) primaryKeyMap.get("_id"));
    }

    // ===================================================================================
    //                                                                               Build

    K key = secondEntry.getKey();
    SortedMap<K, V> subMap = map.tailMap(key);
    V value = getValueNotInPopulatedMap();
    subMap.put(key, value);
    assertEquals(secondEntry.getValue(), value);
    assertEquals(map.get(key), value);
    assertThrows(IllegalArgumentException.class, () -> subMap.put(firstEntry.getKey(), value));
  }

  public void testTailMapRemoveThrough() {
    SortedMap<K, V> map;
    try {

    }

    void write(ByteBuffer input) {
      int remaining = input.remaining();
      if (count + remaining > buf.length) {
        buf = Arrays.copyOf(buf, count + remaining);
      }
      input.get(buf, count, remaining);
      count += remaining;
    }

    byte[] byteArray() {
      return buf;
    }

    int length() {
      return count;
    }
  }

  /** Returns an iterable whose iterator returns the given elements in order. */
  public static <E extends @Nullable Object> MinimalIterable<E> of(E... elements) {
    // Make sure to get an unmodifiable iterator
    return new MinimalIterable<>(asList(elements).iterator());
  }

  /**
   * Returns an iterable whose iterator returns the given elements in order. The elements are copied

    K key = secondEntry.getKey();
    SortedMap<K, V> subMap = map.tailMap(key);
    V value = getValueNotInPopulatedMap();
    subMap.put(key, value);
    assertEquals(secondEntry.getValue(), value);
    assertEquals(map.get(key), value);
    assertThrows(IllegalArgumentException.class, () -> subMap.put(firstEntry.getKey(), value));
  }

  public void testTailMapRemoveThrough() {
    SortedMap<K, V> map;
    try {

///

/// info

In this example we use invented custom headers `X-Key` and `X-Token`.

But in real cases, when implementing security, you would get more benefits from using the integrated [Security utilities (the next chapter)](../security/index.md){.internal-link target=_blank}.

///

## Dependencies errors and return values { #dependencies-errors-and-return-values }