digraph classification {
	edge [ arrowhead="none" ];
	1 [ label="Kryptologie" ];
	2 [ label="Kryptographie" ];
	3 [ label="Kryptoanalyse" ];
	4 [ label="symmetrische\nChiffren" ];
	5 [ label="asymmetrische\nChiffren" ];
	6 [ label="Protokolle\n& Sonstiges" ];

	{
		rank=same;
		2;
		3;
	}
	{
		rank=same;
		4;
		5;
		6;
	}

	1 -> 2;
	1 -> 3;

	2 -> 4;
	2 -> 5;
	2 -> 6;
}