})
	if err != nil {
		return nil, err
	}
	if len(metadata) > MaxMetadataSize {
		return nil, errors.New("config: encryption metadata is too large")
	}
	header[0] = Version
	binary.LittleEndian.PutUint32(header[1:], uint32(len(metadata)))
	buffer.Write(header[:])
	buffer.Write(metadata)

	return io.MultiReader(
		&buffer,
		stream.EncryptReader(plaintext, nonce, nil),
	), nil
}

	}
	return nil
}

// DerivePartKey derives an unique 256 bit key from an ObjectKey and the part index.
func (key ObjectKey) DerivePartKey(id uint32) (partKey [32]byte) {
	var bin [4]byte
	binary.LittleEndian.PutUint32(bin[:], id)

	mac := hmac.New(sha256.New, key[:])
	mac.Write(bin[:])
	mac.Sum(partKey[:0])
	return partKey
}

// SealETag seals the etag using the object key.

		dst = msgp.AppendBytes(dst, ver.meta)
	}

	// Update size...
	binary.BigEndian.PutUint32(dst[dataOffset-4:dataOffset], uint32(len(dst)-dataOffset))

	// Add CRC of metadata as fixed size (5 bytes)
	// Prior to v1.3 this was variable sized.
	tmp = tmp[:5]
	tmp[0] = 0xce // muint32
	binary.BigEndian.PutUint32(tmp[1:], uint32(xxhash.Sum64(dst[dataOffset:])))
	dst = append(dst, tmp[:5]...)

	objectEncryptionKey                []byte
	partDecRelOffset, partEncRelOffset int64
}

func (d *DecryptBlocksReader) buildDecrypter(partID int) error {
	var partIDbin [4]byte
	binary.LittleEndian.PutUint32(partIDbin[:], uint32(partID)) // marshal part ID

	mac := hmac.New(sha256.New, d.objectEncryptionKey) // derive part encryption key from part ID and object key
	mac.Write(partIDbin[:])
	partEncryptionKey := mac.Sum(nil)

				} else {
					write([]byte{0})
				}
				xioutil.SafeClose(doneCh)
				return
			case block := <-blockCh:
				var tmp [5]byte
				tmp[0] = 2
				binary.LittleEndian.PutUint32(tmp[1:], uint32(len(block)))
				write(tmp[:])
				write(block)
				if canWrite {
					xhttp.Flush(w)
				}
			}
		}
	}()
	return &h
}

var poolBuf8k = bpool.Pool[*[]byte]{

	if err != ErrFormat {
		t.Errorf("zeroes: error=%v, want %v", err, ErrFormat)
	}

	// repeated directoryEndSignatures
	sig := make([]byte, 4)
	binary.LittleEndian.PutUint32(sig, directoryEndSignature)
	for i := 0; i < size-4; i += 4 {
		copy(b[i:i+4], sig)
	}
	_, err = NewReader(bytes.NewReader(b), size)
	if err != ErrFormat {
		t.Errorf("sigs: error=%v, want %v", err, ErrFormat)