\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,angles,quotes}

\begin{document}
	\begin{tikzpicture}[thick]
		\draw[dashed] (0,0) -- node[at end, above]{Verifier}(0,4);
		\draw[dashed,black!20] (3,0) -- node[at end, above]{Prover}(3,4);
		\draw[dashed] (5,0) -- node[at end, above]{Attacker}(5,4);
		\draw[-latex] (0,3) -- (3,2.5);
		\draw[-latex] (3,1.5) -- (0,1);

		\draw[decoration={brace,raise=5pt},decorate,black!20](3,2.5)
		-- node[right=6pt,black!20] {$t_p$}(3,1.5);

		\draw[-latex] (3,2.5) -- (5,2.167);
		\draw[-latex] (5,1.833) -- (3,1.5);

		\draw[decoration={brace,raise=5pt},decorate,black!20](5,2.167)
		-- node[right=6pt,black!20] {$t_p^\prime$}(5,1.833);

		\draw[decoration={brace,mirror,raise=5pt},decorate](0,3)
		-- node[left=6pt] {$t_{ToF}$}(0,1);

		\draw[decoration={brace,mirror,raise=5pt},black!20,decorate](0,0)
		-- node[below=6pt,black!20] {$d$}(3,0);

		\draw[decoration={brace,mirror,raise=5pt},decorate](0,-0.5)
		-- node[below=6pt] {$d^\prime$}(5,-0.5);

	\end{tikzpicture}
\end{document}