\begin{table}[h] \footnotesize \centering \begin{tabularx}{\columnwidth}{l!{\color{black!70}\vrule width 0.4pt\hspace{0.5em}}cccccc} \toprule \textbf{Compromise Scenario} & \textbf{P2} & \textbf{P3} & \textbf{P4} & \textbf{P5} & \textbf{P6} & \textbf{P7} \\ & \textit{Secr.} & \textit{Auth.} & \textit{Deni.} & \textit{PFS} & \textit{PCS} & \textit{S-Deni.} \\ \midrule \multicolumn{7}{l}{\textit{Megolm}} \\ C1: Fan-out ratchet key & \ding{55} & \ding{51} & \ding{51} & \ding{51} & \ding{51} & \ding{51} \\ C2: Fan-out public signing key & \ding{51} & \ding{51} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ C3: Fan-out private signing key & \ding{51} & \ding{51}$^*$ & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ C4: Complete fan-out session & \ding{55} & \ding{55} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ C5: P2P identity keys (mutual) & \ding{51} & \ding{51} & \ding{51} & \ding{51} & \ding{51} & \ding{51} \\ C6: P2P chain key & \ding{55} & \ding{55} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ C7: P2P pre-key + identity & \ding{55} & \ding{55} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ \midrule \multicolumn{7}{l}{\textit{Sender Keys}} \\ C1: Fan-out ratchet key & \ding{55} & \ding{51} & \ding{51} & \ding{51} & \ding{51} & \ding{51} \\ C2: Fan-out public signing key & \ding{51} & \ding{51} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ C3: Fan-out private signing key & \ding{51} & \ding{55} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ C4: Complete fan-out session & \ding{55} & \ding{55} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ C5: P2P identity keys (mutual) & \ding{51} & \ding{51} & \ding{51} & \ding{51} & \ding{51} & \ding{51} \\ C6: P2P chain key & \ding{55} & \ding{55} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ C7: P2P pre-key + identity & \ding{55} & \ding{55} & \ding{55} & \ding{51} & \ding{51} & \ding{55} \\ \bottomrule \end{tabularx} \caption{Security property preservation under compromise scenarios. \ding{51} = property maintained, \ding{55} = property violated. $^*$Megolm maintains authentication in C3 due to MAC verification, unlike Sender Keys which relies solely on signatures. P2: Message Secrecy, P3: Authentication, P4: Deniability, P5: Perfect Forward Secrecy, P6: Post-Compromise Security, P7: Strong Deniability. ``P1: Reachability'' remains all true for all cases, and ``P2: Mutual Deniability'' remains false for all cases, thus both properties are not included in the table.} \label{tab:failure-comparison} \end{table}