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Constrain preimage request lengths below state-key discriminators #542

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Constrain preimage request lengths below state-key discriminators #542

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7cb1dca
Constrain preimage request lengths below state-key discriminators
philoniare Jul 28, 2026
928ad8b
Name the set of allowed preimage lengths as \preimagelen
philoniare Aug 3, 2026
ea1f002
Address review: relocate \preimagelen definition and drop redundant l…
philoniare Aug 5, 2026
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1 change: 1 addition & 0 deletions preamble.tex
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Expand Up @@ -407,6 +407,7 @@
\newcommand*{\balance}{\N_B}
\newcommand*{\serviceid}{\N_S}
\newcommand*{\bloblength}{\N_L}
\newcommand*{\preimagelen}{\N_P}
\newcommand*{\gas}{\N_G}
\newcommand*{\Nmax}[1]{\N_{#1}}
\newcommand*{\Nclamp}[2]{\N_{#1 \dots #2}}
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7 changes: 6 additions & 1 deletion text/accounts.tex
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Expand Up @@ -13,7 +13,7 @@ \section{Service Accounts}\label{sec:accounts}
\serviceaccount \equiv \tuple{\ \begin{aligned}
\sa¬storage &\in \dictionary{\blob}{\blob}\,,\
\sa¬preimages \in \dictionary{\hash}{\blob}\,,\\
\sa¬requests &\in \dictionary{\tuple{\hash,\bloblength}}{\sequence[:3]{\timeslot}}\,,\\
\sa¬requests &\in \dictionary{\tuple{\hash,\preimagelen}}{\sequence[:3]{\timeslot}}\,,\\
\sa¬gratis &\in \balance\,,\
\sa¬codehash \in \hash\,,\
\sa¬balance \in \balance\,,\
Expand All @@ -26,6 +26,11 @@ \section{Service Accounts}\label{sec:accounts}
\end{aligned}\,}
\end{align}

Here, $\preimagelen$ is the set of lengths under which a preimage may be solicited; this is the subset of $\bloblength$ omitting its two greatest values, since these are reserved as the discriminators of storage and preimage items respectively in the state-key derivation of equation \ref{eq:stateserialization}. Formally:
\begin{align}\label{eq:preimagelen}
\preimagelen &\equiv \Nmax{2^{32} - 2}
\end{align}

Thus, the balance of the service of index $s$ would be denoted $\accounts\subb{s}_\sa¬balance$ and the storage item of key $\mathbf{k} \in \blob$ for that service is written $\accounts\subb{s}_\sa¬storage\subb{\mathbf{k}}$.


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1 change: 1 addition & 0 deletions text/definitions.tex
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Expand Up @@ -11,6 +11,7 @@ \subsubsection{Regular Notation}
\item[$\balance$] The set of balance values. Equivalent to $\Nbits{64}$. See equation \ref{eq:balance}.
\item[$\gas$] The set of unsigned gas values. Equivalent to $\Nbits{64}$. See equation \ref{eq:gasregentry}.
\item[$\bloblength$] The set of blob length values. Equivalent to $\Nbits{32}$. See section \ref{sec:numbers}.
\item[$\preimagelen$] The set of lengths under which a preimage may be solicited. A subset of $\bloblength$, equivalent to $\Nmax{2^{32} - 2}$. See equation \ref{eq:preimagelen}.
\item[$\pvmreg$] The set of register values. Equivalent to $\Nbits{64}$. See equation \ref{eq:gasregentry}.
\item[$\serviceid$] The set from which service indices are drawn. Equivalent to $\Nbits{32}$. See section \ref{eq:serviceaccounts}.
\item[$\timeslot$] The set of timeslot values. Equivalent to $\Nbits{32}$. See equation \ref{eq:time}.
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2 changes: 1 addition & 1 deletion text/merklization.tex
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Expand Up @@ -17,7 +17,7 @@ \subsection{Serialization}
\end{equation}

The state serialization is then defined as the dictionary built from the amalgamation of each of the components. Cryptographic hashing ensures that there will be no duplicate state-keys given that there are no duplicate inputs to $C$. Formally, we define $T$ which transforms some state $\thestate$ into its serialized form:
\begin{equation}
\begin{equation}\label{eq:stateserialization}
T(\thestate) \equiv \abracegroup{
&&C(1) &\mapsto \encode{\sq{\build{\var{x}}{x \orderedin \authpool}}} \;, \\
&&C(2) &\mapsto \encode{\authqueue} \;, \\
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13 changes: 7 additions & 6 deletions text/pvm_invocations.tex
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Expand Up @@ -789,7 +789,7 @@ \subsubsection{Accumulate Functions}\label{sec:accumulatefunctions}
$\begin{aligned}
\using \sq{o, l, \sa¬minaccgas, \sa¬minmemogas, \sa¬gratis, \local¬desiredid} &= \registers\subrange{7}{6} \\
\using \sa¬codehash &= \begin{cases}
\memory\subrange{o}{32} &\when \Nrange{o}{32} \subseteq \readable{\memory} \wedge l \in \Nbits{32} \\
\memory\subrange{o}{32} &\when \Nrange{o}{32} \subseteq \readable{\memory} \\
\error &\otherwise
\end{cases}\\
\using \mathbf{a} \in \serviceaccount \cup \set{\error} &= \begin{cases}
Expand All @@ -810,7 +810,8 @@ \subsubsection{Accumulate Functions}\label{sec:accumulatefunctions}
\end{cases} \\
\using \mathbf{s} &= \imX_\im¬self \exc \mathbf{s}_\sa¬balance = (\imX_\im¬self)_\sa¬balance - \mathbf{a}_\sa¬minbalance \\
\tup{\execst', \registers'_7, \imX'_\im¬nextfreeid, (\imX'_\im¬state)_\ps¬accounts} &\equiv \begin{cases}
\tup{\panic, \registers_7, \imX_\im¬nextfreeid, (\imX_\im¬state)_\ps¬accounts} &\when c = \error \\
\tup{\continue, \mathtt{HUH}, \imX_\im¬nextfreeid, (\imX_\im¬state)_\ps¬accounts} &\when l \not\in \preimagelen \\
\tup{\panic, \registers_7, \imX_\im¬nextfreeid, (\imX_\im¬state)_\ps¬accounts} &\otherwhen c = \error \\
\tup{\continue, \mathtt{HUH}, \imX_\im¬nextfreeid, (\imX_\im¬state)_\ps¬accounts} &\otherwhen f \ne 0 \wedge \imX_\im¬id \ne (\imX_\im¬state)_\ps¬manager \\
\tup{\continue, \mathtt{CASH}, \imX_\im¬nextfreeid, (\imX_\im¬state)_\ps¬accounts} &\otherwhen \mathbf{s}_\sa¬balance < (\imX_\im¬self)_\sa¬minbalance \\
\tup{\continue, \mathtt{FULL}, \imX_\im¬nextfreeid, (\imX_\im¬state)_\ps¬accounts} &\otherwhen \imX_\im¬id = (\imX_\im¬state)_\ps¬registrar \wedge \local¬desiredid < \Cminpublicindex \wedge \local¬desiredid \in \keys{(\imX_\im¬state)_\ps¬accounts} \\
Expand Down Expand Up @@ -910,7 +911,7 @@ \subsubsection{Accumulate Functions}\label{sec:accumulatefunctions}
\error &\otherwise\\
\end{cases} \\
\tup{\execst', \registers'_7, \registers'_8} &\equiv \begin{cases}
\tup{\continue, \mathtt{HUH}, \registers_8} &\when z \not\in \bloblength \\
\tup{\continue, \mathtt{HUH}, \registers_8} &\when z \not\in \preimagelen \\
\tup{\panic, \registers_7, \registers_8} &\otherwhen h = \error \\
\tup{\continue, \mathtt{NONE}, 0} &\otherwhen \mathbf{a} = \error \\
\tup{\continue, 0, 0} &\otherwhen \mathbf{a} = \sq{} \\
Expand All @@ -937,7 +938,7 @@ \subsubsection{Accumulate Functions}\label{sec:accumulatefunctions}
\error &\otherwise\\
\end{cases} \\
\tup{\execst', \registers'_7, \imX'_\im¬self} &\equiv \begin{cases}
\tup{\continue, \mathtt{HUH}, \imX_\im¬self} &\when z \not \in \bloblength \\
\tup{\continue, \mathtt{HUH}, \imX_\im¬self} &\when z \not \in \preimagelen \\
\tup{\panic, \registers_7, \imX_\im¬self} &\otherwhen h = \error \\
\tup{\continue, \mathtt{HUH}, \imX_\im¬self} &\otherwhen \mathbf{a} = \error \\
\tup{\continue, \mathtt{FULL}, \imX_\im¬self} &\otherwhen \mathbf{a}_\sa¬balance < \mathbf{a}_\sa¬minbalance \\
Expand Down Expand Up @@ -968,7 +969,7 @@ \subsubsection{Accumulate Functions}\label{sec:accumulatefunctions}
\error &\otherwise\\
\end{cases} \\
\tup{\execst', \registers'_7, \imX'_\im¬self} &\equiv \begin{cases}
\tup{\continue, \mathtt{HUH}, \imX_\im¬self} &\when z \not \in \bloblength \\
\tup{\continue, \mathtt{HUH}, \imX_\im¬self} &\when z \not \in \preimagelen \\
\tup{\panic, \registers_7, \imX_\im¬self} &\otherwhen h = \error \\
\tup{\continue, \mathtt{HUH}, \imX_\im¬self} &\otherwhen \mathbf{a} = \error \\
\tup{\continue, \mathtt{OK}, \mathbf{a}} &\otherwise \\
Expand Down Expand Up @@ -1011,7 +1012,7 @@ \subsubsection{Accumulate Functions}\label{sec:accumulatefunctions}
\none &\otherwise
\end{cases} \\
\tup{\execst', \registers'_7, \imX'_\im¬provisions} &\equiv \begin{cases}
\tup{\continue, \mathtt{HUH}, \imX_\im¬provisions} &\when z \not \in \bloblength \\
\tup{\continue, \mathtt{HUH}, \imX_\im¬provisions} &\when z \not \in \preimagelen \\
\tup{\panic, \registers_7, \imX_\im¬provisions} &\otherwhen \mathbf{i} = \error \\
\tup{\continue, \mathtt{WHO}, \imX_\im¬provisions} &\otherwhen \mathbf{a} = \none \\
\tup{\continue, \mathtt{HUH}, \imX_\im¬provisions} &\otherwhen \mathbf{a}_\sa¬requests[\tup{\blake{\mathbf{i}}, z}] \ne \sq{} \\
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