\begin{tikzpicture}[
	-latex,
	entity/.style = {
		draw = gray!30,
		thick,
		rounded rectangle,
		fill = white,
		minimum width = 2cm,
		font = \fontsize{8}{8}\selectfont,
		text = white,
	},
	relation/.style = {
		draw = none,
		font = \fontsize{6}{6}\selectfont,
	},
	path/.style = {
		draw,
		thick,
		-latex,
	},
]
	\node[entity, fill=darkBlue] (Publisher) at (0,0) { Publisher };
	\node[entity, fill=darkGreen, below=1.5cm of Publisher] (DNS) {DNS};
	\node[entity, fill=darkOrange, left=1.5cm of Publisher] (Log) {Log};

	% Setup DNS
	\path[path, dashed] (Publisher) --
			node[relation, right] {TXT RR}
		(DNS);
	
	\path[path] (Publisher) edge[bend right]
			node[relation, above] {
				Key-value pairs
			}
		(Log);
	\path[path] (Log) edge[bend right]
			node[relation,below] {
				accept/reject
			}
		(Publisher);
	
	\path[path, rounded corners] (Log) |-
			node[relation,below,pos=.75]{
				verify TXT RR
			}
		(DNS);
\end{tikzpicture}