papers/lp-223-p3q-pulsar/sections/03-pulsar-kind.tex

\section{Pulsar Kind ($\textnormal{kind} = 0x01$)}
\label{sec:pulsar-kind}

\subsection{Slot and ABI}

\texttt{0x012205} with leading \texttt{kind=0x01}. The Solidity
shim is:

\begin{lstlisting}[language={}]
// EVM precompile at slot 0x012205, kind = 0x01
bool ok = P3Q.verify(
    0x01,                        // Pulsar kind
    pulsarSig,                   // FIPS-204 ML-DSA-{44|65|87} sig
    messageHash,                 // H(prev_root || new_root || batch_hash)
    groupPubKey                  // Pulsar group public key
);
\end{lstlisting}

The kind byte at offset~0 selects dispatch into the Pulsar
verifier; the mode byte at offset~1 selects which FIPS-204
parameter set is in play.

\subsection{Wire format}

The full \SI{5303}{B} canonical input for ML-DSA-65 (the
production target):

\begin{table}[h]
\centering
\small
\begin{tabular}{@{}rrl@{}}
\toprule
\textbf{Offset} & \textbf{Size} & \textbf{Field} \\
\midrule
0 & 1 & \texttt{kind = 0x01} \\
1 & 1 & \texttt{mode} (\texttt{0x44}/\texttt{0x65}/\texttt{0x87} = ML-DSA-44/65/87) \\
2 & 4 & \texttt{sigLen} (BE32) \\
6 & \texttt{sigLen} & \texttt{pulsarSig} (\SI{3309}{B} for ML-DSA-65) \\
$6{+}\textit{sigLen}$ & 4 & \texttt{pkLen} (BE32) \\
$10{+}\textit{sigLen}$ & \texttt{pkLen} & \texttt{groupPubKey} (\SI{1952}{B} for ML-DSA-65) \\
$10{+}\textit{sigLen}{+}\textit{pkLen}$ & 32 & \texttt{messageHash} \\
\bottomrule
\end{tabular}
\caption{Pulsar-kind wire format. Total at ML-DSA-65:
$1+1+4+3309+4+1952+32 = \SI{5303}{B}$.}
\label{tab:pulsar-wire}
\end{table}

Trailing bytes after the messageHash are accepted as padding to
match the convention used by the sibling STARK-FRI precompile;
padding does not affect verification.

\subsection{Verifier core}

The Pulsar verifier core IS the FIPS-204 ML-DSA verifier. Pulsar
signatures serialize byte-identically to FIPS-204 ML-DSA
signatures per LP-073~\cite{lp073} -- the Pulsar threshold
ceremony's Class-N1 claim is that the aggregated signature is
byte-equal to a single-party FIPS-204 ML-DSA signature on the
same message and group public key. Any conformant FIPS-204
verifier suffices; the reference implementation at
\texttt{lux/precompile/p3q/contract.go::Run} dispatches via
\texttt{mldsa.PublicKeyFromBytes(...) + pk.VerifySignatureCtx(...)},
which is a thin alias over the cloudflare/circl FIPS-204
implementation.

The Pulsar kind is the only kind wired into the \emph{P3Q} dispatch
today. Corona ($0x02$) and Magnetar ($0x03$) reserve their P3Q dispatch
entries and return \texttt{abiFalse} via the
\texttt{ErrKindNotImplemented} path until those dispatches are wired.
Note this concerns only the \emph{unified P3Q slot}: Corona's threshold
library has landed and its \emph{dedicated} precompile (Corona at
\texttt{0x012206}) is wired. Magnetar's threshold library has not yet
landed --- full no-reconstruct threshold SLH-DSA is an open problem, so
Magnetar stays fail-closed on every path. See LP-220 and~LP-222.

\subsection{Gas cost}

\textbf{\SI{50000}{gas}} base $+$ \SI{10}{gas/byte} per-byte
adder. At the canonical \SI{5303}{B} input, total gas is
$50000 + 5303 \times 10 = \SI{103030}{gas}$. This is well under
the \SI{12}{M} C-Chain block-gas-limit (\textasciitilde 116
verifies per block; per the audit at
\texttt{contract.FeeConfigReporter}). The gas calibration is
$10\times$ the BLS pairing verify charge of \SI{5000}{gas},
reflecting lattice verification's inherent cost (NTT inverse +
matrix-vector multiplication mod $q$).

\subsection{Domain separation}

Every Pulsar-kind verify binds the FIPS-204 context string
\texttt{lux-evm-precompile-p3q-v1}. Mismatched context between
signer and verifier causes the FIPS-204 verifier to reject. This
prevents cross-precompile replay: a Pulsar signature minted for
the LP-0120 raw-Pulsar precompile at \texttt{0x012204} (which
uses context \texttt{lux-evm-precompile-pulsar-v1}) cannot be
re-submitted to the rollup-batch P3Q path at \texttt{0x012205}.

\subsection{Performance}

\begin{table}[h]
\centering
\small
\begin{tabular}{@{}lrrl@{}}
\toprule
\textbf{Metric} & \textbf{M1 Max} & \textbf{Spark} & \textbf{Source} \\
\midrule
Per-validator Pulsar sign at $N{=}64$ & \SI{391}{\milli\second} & \SI{585}{\milli\second} & matrix bench (measured)~\cite{parityaudit} \\
CPU verify (single sig) & $\sim$\SI{80}{\micro\second} & $\sim$\SI{80}{\micro\second} & circl benchmark (measured) \\
Blackwell sm\_120 verify & --- & $\sim$\SI{50}{\micro\second} & projected (LP-203 kernel) \\
Blackwell sm\_120 batched ($N{=}64$) & --- & $\sim$\SI{5}{\milli\second} aggregate & projected \\
\bottomrule
\end{tabular}
\caption{Pulsar kind performance. Sign times are measured per
the Quasar 4-scheme matrix bench (mean of 50 rounds at $N{=}64$);
verify times tagged ``projected'' have not been exercised in the
matrix bench (GPU dispatch boundary gap, see
section~\ref{sec:pulsar-perf-note}).}
\label{tab:pulsar-perf}
\end{table}

\subsubsection{Note on GPU verify projection}
\label{sec:pulsar-perf-note}

The Blackwell verify numbers cited in earlier LP-203 drafts
(\textasciitilde\SI{50}{\micro\second} single,
\textasciitilde\SI{5}{\milli\second} batched) are kernel-level
micro-benchmarks, not end-to-end measurements through the
precompile entry-point. The matrix bench captured \num{4595}
\texttt{nvidia-smi dmon} samples during the 2-hour Spark run:
mean \texttt{SM\%} = \SI{11.9}{\percent} (idle/background only).
Until \texttt{lux-lattice.pc} is installed on Spark and
\texttt{lux\_pulsar\_verify\_batch} is exposed in
\texttt{lux/accel/c\_api.h}, GPU verify timings remain
projections.

\subsection{Use case}

Pulsar-kind is the default PQ-fast verifier for any rollup that
wants Module-LWE-grade PQ assurance on its batch envelope
without paying the cross-family premium of Corona or Magnetar.
Per LP-217, PQ-fast (BLS + Pulsar) is the recommended mode for
payment rails, gaming, and DEX matching. The gas cost is
$\sim$\SI{108000}{} per batch (the \SI{103030}{gas} Pulsar verify
plus the \SI{5000}{gas} BLS pairing verify), well below the
$\sim$\SI{5}{M} cost of adding Corona.

LP-218 specifies the Pulsar kind in detail as part of the
rollup-batch envelope pattern; this section restates the
Pulsar-kind facts in the LP-220 per-kind structure so the three
kinds are commensurable in one document.