// values appropriately.
		d.partEncRelOffset = 0
		d.partDecRelOffset = 0
		d.startSeqNum = 0

		d.partIndex++
		if d.partIndex == len(d.parts) {
			return n1, io.EOF
		}

		err = d.buildDecrypter(d.parts[d.partIndex].Number)
		if err != nil {
			return 0, err
		}

		n1, err = d.decrypter.Read(p[n1:])
		if err != nil {
			return 0, err
		}