draw security protocol

Question

It's about authenticated key exchange protocol, there are two parties party A and party B,they exchange some messages. At the end they compute the shared keys SK.

I know that it's vey cool to use Latex to set type, I really want to learn it. Any one can give me some advices? please help me! thanks

Answer 1

The symbols are not very clear in the image; just change them if needed.

The idea is to build an array with three columns.

\documentclass{article}
\usepackage{amsmath,amssymb,booktabs}
\begin{document}
\[
\begin{array}{@{}l@{}c@{}l@{}}
\toprule
\hat{A} && \hat{B} \\
A_1=g^{a_1},\quad A_2=g^{a_2} &&
B_1=g^{b_1},\quad B_2=g^{b_2} \\
\bar{x}\gets_R \mathbb{Z}_q,\quad x=H_1(\bar{x},a_1,a_2) &&
\bar{y}\gets_R \mathbb{Z}_q,\quad y=H_1(\bar{y},b_1,b_2) \\
& \xrightarrow{\textstyle X=g^x} \\
& \xleftarrow {\textstyle Y=g^y} \\
\mathit{sid}=(X,Y,\hat{A},\hat{B}) &&
\mathit{sid}=(X,Y,\hat{A},\hat{B}) \\
Z_1=(YB_1)^x,\quad Z_2=(YB_2)^x &&
Z_1=X^{y+b_1},\quad Z_2=X^{y+b_2} \\
Z_3=Y^{x+a_1},\quad Z_4=Y^{x+a_2} &&
Z_3=(XA_1)^y,\quad Z_4=(XA_2)^y \\
\mathit{SK}=H(Z_1,Z_2,Z_3,Z_4,\mathit{sid}) &&
\mathit{SK}=H(Z_1,Z_2,Z_3,Z_4,\mathit{sid}) \\
\bottomrule
\end{array}
\]
\end{document}