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masterthesis/thesis/sections/security_of_eddsa/gamez_implies_uf-nma.tex

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\subsection{\igame $=>$ UF-NMA (ROM)}
This section shows that \igame implies the UF-NMA security if the EdDSA signature scheme using the Algebraic Group Model. The section starts by first providing an intuition if the proof followed by the detailed security proof.
\begin{figure}
\hrule
\begin{multicols}{2}
\large
\begin{algorithmic}[1]
\Statex \underline{\game \igame}
\State \quad $a \randomsample \{2^{n-1}, 2^{n-1} + 8, ..., 2^n - 8\}$
\State \quad $\groupelement{A} \assign a \groupelement{B}$
\State \quad $s^* \randomsample \adversary{A}^{\ioracle(\inp)}(\groupelement{A})$
\State \quad \Return $\exists \groupelement{R}^*, \ch^*: \groupelement{R}^* = 2^c (s^* \groupelement{B} - \ch^* \groupelement{A}) \wedge (\groupelement{R}^*, \ch^*) \in Q$
\end{algorithmic}
\columnbreak
\begin{algorithmic}[1]
\Statex \underline{\oracle \ioracle($\groupelement{R_i} \in \group{G}$)}
\State \quad $\ch_i \randomsample \{0,1\}^{2b}$
\State \quad $Q \assign Q \cup \{ (\groupelement{R}_i, \ch_i) \}$
\State \quad \Return $\ch_i$
\end{algorithmic}
\end{multicols}
\hrule
\caption{\igame}
\label{game:igame}
\end{figure}