From 917dbf5c46d149f2ca5efa0d70d5c843edba4a21 Mon Sep 17 00:00:00 2001
From: Daira Hopwood <daira@jacaranda.org>
Date: Fri, 6 Nov 2020 00:30:52 +0000
Subject: [PATCH] Add a missing consensus rule that has always been implemented
 in zcashd: there must be at least one transparent output, Sapling output, or
 JoinSplit in a transaction.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
---
 protocol/protocol.tex | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/protocol/protocol.tex b/protocol/protocol.tex
index 5b165cfa..b0337d13 100644
--- a/protocol/protocol.tex
+++ b/protocol/protocol.tex
@@ -897,8 +897,8 @@ electronic commerce and payment, financial privacy, proof of work, zero knowledg
 \newcommand{\transparentTxValuePool}{\termandindex{transparent transaction value pool}{transaction value pool (transparent)}}
 % There is no Sprout transaction value pool, since JoinSplits are balanced individually.
 \newcommand{\SaplingTxValuePool}{\termandindex{\textbf{Sapling} transaction value pool}{transaction value pool (Sapling)}}
-\newcommand{\SproutChainValuePoolTotal}{\termandindex{\textbf{Sapling} chain value pool total}{chain value pool total (Sapling)}}
-\newcommand{\SaplingChainValuePoolTotal}{\termandindex{\textbf{Sapling} chain value pool total}{chain value pool total (Sapling)}}
+\newcommand{\SproutChainValuePoolBalance}{\termandindex{\textbf{Sprout} chain value pool balance}{chain value pool balance (Sprout)}}
+\newcommand{\SaplingChainValuePoolBalance}{\termandindex{\textbf{Sapling} chain value pool balance}{chain value pool balance (Sapling)}}
 \newcommand{\shielded}{\term{shielded}}
 \newcommand{\xShielded}{\termx{shielded}}
 \newcommand{\blockChain}{\term{block chain}}
@@ -9118,18 +9118,20 @@ $\versionField \geq 4$ and $\nShieldedSpend + \nShieldedOutput > 0$.
         be $\hexint{892F2085}$.}
   \presaplingitem{The encoded size of the \transaction{} \MUST be less than or equal to
         $100000$ bytes.}
-  \presaplingitem{If $\versionField = 1$ or $\nJoinSplit = 0$, then \txInCount{} \MUSTNOT be $0$.}
+  \presaplingitem{If $\versionField = 1$ or $\nJoinSplit = 0$, then both \txInCount{} and \txOutCount{} \MUST be nonzero.\!}
   \saplingonwarditem{At least one of \txInCount, \nShieldedSpend, and \nJoinSplit{} \MUST be nonzero.}
+  \saplingonwarditem{At least one of \txOutCount, \nShieldedOutput, and \nJoinSplit{} \MUST be nonzero.}
   \item A \transaction with one or more \transparent inputs from \coinbaseTransactions{} \MUST have no
-        \transparent outputs (i.e.\ \txOutCount{} \MUST be $0$). Note that inputs from
+        \transparent outputs (i.e.\ \txOutCount{} \MUST be $0$). Inputs from
         \coinbaseTransactions include \foundersReward outputs.
   \item If $\versionField \geq 2$ and $\nJoinSplit > 0$, then:
         \begin{itemize}
-          \item \joinSplitPubKey{} \MUST represent a valid encoding (as specified in \crossref{concretejssig}) of
+          \item \joinSplitPubKey{} \MUST be a valid encoding (see \crossref{concretejssig}) of
                 an \EdSpecific \validatingKey.
           \item \joinSplitSig{} \MUST represent a valid signature under \joinSplitPubKey{} of
                 $\dataToBeSigned$, as defined in \crossref{sproutnonmalleability}.
         \end{itemize}
+        \vspace{-1ex}
   \saplingonwarditem{If $\versionField \geq 4$ and $\nShieldedSpend + \nShieldedOutput > 0$,
         then:
         \begin{itemize}
@@ -9138,6 +9140,7 @@ $\versionField \geq 4$ and $\nShieldedSpend + \nShieldedOutput > 0$.
                 $\BindingPublic$ of $\SigHash$ ---
                 i.e.\ $\BindingSigValidate{\BindingPublic}(\SigHash, \bindingSig) = 1$.
         \end{itemize}}
+        \vspace{-1ex}
   \saplingonwarditem{If $\versionField \geq 4$ and $\nShieldedSpend + \nShieldedOutput = 0$,
         then $\valueBalance$ \MUST be $0$.}
   \item The total amount of \transparentOutputs from a \coinbaseTransaction,\heartwood{ minus
@@ -10875,6 +10878,9 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
 
 \historyentry{2020.1.15}{}
 \begin{itemize}
+    \item Add a missing consensus rule that has always been implemented in \zcashd: there
+          must be at least one \transparentOutput, \outputDescription, or \joinSplitDescription
+          in a \transaction.
     \item Define \SproutChainValuePoolBalance\sapling{ and \SaplingChainValuePoolBalance,} and include
           consensus rules from \cite{ZIP-209}.
 \sapling{