Minor clarifications.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

protocol/protocol.tex

@@ -410,6 +410,7 @@ electronic commerce and payment, financial privacy, proof of work, zero knowledg
 \newcommand{\commitmentTrapdoor}{\term{commitment trapdoor}}
 \newcommand{\commitmentTrapdoors}{\term{commitment trapdoors}}
 \newcommand{\trapdoor}{\term{trapdoor}}
+\newcommand{\xCommitment}{\term{commitment}}
 \newcommand{\noteCommitment}{\term{note commitment}}
 \newcommand{\noteCommitments}{\term{note commitments}}
 \newcommand{\xNoteCommitments}{\term{Note commitments}}
@@ -1294,6 +1295,7 @@ electronic commerce and payment, financial privacy, proof of work, zero knowledg
 \newcommand{\MerkleDepth}{\mathsf{MerkleDepth}}
 \newcommand{\MerkleDepthSprout}{\optSprout{\MerkleDepth}}
 \newcommand{\MerkleDepthSapling}{\MerkleDepth^\mathsf{Sapling}}
+\newcommand{\MerkleDepthSproutOrSapling}{\MerkleDepth^\mathsf{Sprout\sapling{,Sapling}}}
 \newcommand{\MerkleNode}[2]{\mathsf{M}^{#1}_{#2}}
 \newcommand{\MerkleSibling}{\mathsf{sibling}}
 \newcommand{\MerkleCRH}{\mathsf{MerkleCRH}}
@@ -2297,7 +2299,7 @@ where $\NoteCommitSapling{}$ is instantiated in \crossref{concretewindowedcommit
 Notice that the above definition of a \Sapling \note does not have a
 $\NoteAddressRand$ field. There is in fact a $\NoteAddressRand$ value associated
 with each \Sapling \note, but this only be computed once its position in the
-\noteCommitmentTree is known (see \crossref{blockchain} and \crossref{transactions}).
+\noteCommitmentTree is known (see \crossref{transactions} and \crossref{merkletree}).
 We refer to the combination of a \note and its \notePosition $\NotePosition$, as a
 \positionedNote.
 
@@ -2532,8 +2534,8 @@ for the whole \transaction to balance.
 
 \vspace{1.5ex}
 \begin{consensusrules}
-  \item \transaction{} \MUST balance as specified in \crossref{saplingbalance}.
-  \item The \anchor of each \spendDescription{} \MUST refer to some earlier \block's final
+  \item \vspace{-0.5ex} The \transaction{} \MUST balance as specified in \crossref{saplingbalance}.
+  \item \vspace{-0.5ex} The \anchor of each \spendDescription{} \MUST refer to some earlier \block's final
         \Sapling \treestate.
 \end{consensusrules}
 } %sapling
@@ -2543,7 +2545,7 @@ for the whole \transaction to balance.
 
 \vspace{-2ex}
 \begin{center}
-\includegraphics[scale=.4,interpolate]{incremental_merkle}
+\includegraphics[scale=.35,interpolate]{incremental_merkle}
 \end{center}
 \vspace{-2ex}
 %\sapling{\todo{The commitment indices in the above diagram should be zero-based to reflect the \notePosition{}.}}
@@ -2565,6 +2567,9 @@ $2^h$ \merkleNodes with \merkleIndices $0$ to $2^h-1$ inclusive.
 The \merkleHash associated with the \merkleNode at \merkleIndex $i$ in \merkleLayer $h$
 is denoted $\MerkleNode{h}{i}$.
 
+The index of a \note's \xCommitment at the leafmost layer
+($\MerkleDepthSproutOrSapling$) is called its \notePosition.
+
 
 \subsection{\NullifierSets} \label{nullifierset}
 
@@ -3755,12 +3760,12 @@ where
   \item $\cm \typecolon \NoteCommitSaplingOutput$ is the \noteCommitment for the output \note;
   \item $\EphemeralPublic \typecolon \KASaplingPublic$ is
         a key agreement public key, used to derive the key for encryption
-        of the \notesCiphertext (\crossref{saplinginband});
+        of the \noteCiphertext (\crossref{saplinginband});
   \item $\TransmitCiphertext{} \typecolon \Ciphertext$ is
         a ciphertext component for the encrypted output \note;
   \item $\OutCiphertext{} \typecolon \Ciphertext$ is a ciphertext component that allows the holder of
         a \fullViewingKey to recover the recipient \diversifiedTransmissionKey $\DiversifiedTransmitPublic$
-        and the ephemeral private key $\EphemeralPrivate$;
+        and the ephemeral private key $\EphemeralPrivate$ (and therefore the entire \notePlaintext);
   \item $\ProofOutput \typecolon \OutputProof$ is a \zeroKnowledgeProof with \primaryInput
         $(\cv, \cm, \EphemeralPublic)$ for the \outputStatement defined in \crossref{outputstatement}.
 \end{itemize}
@@ -3950,7 +3955,7 @@ A \dummy{} \Sapling input \note is constructed as follows:
                                                                           \vOld{})$.
   \item Compute $\nfOld{} = \PRFnfSapling{\AuthProvePublicRepr}(\reprJ(\NoteAddressRand))$.
   \item Construct a \dummy \merklePath $\TreePath{}$ for use in the
-        \auxiliaryInput to the \spendStatement (this will not be checked).
+        \auxiliaryInput to the \spendStatement (this will not be checked, because $\vOld{} = 0$).
 \end{itemize}
 
 As in \Sprout, a \dummy{} \Sapling output \note is constructed as normal but with
@@ -8993,6 +8998,16 @@ found by Brian Warner.
 \intropart
 \section{Change History}
 
+\subparagraph{2018.0-beta-19}
+
+\begin{itemize}
+    \item No changes to \Sprout.
+\sapling{
+    \item Minor clarifications.
+} %sapling
+\end{itemize}
+
+\introlist
 \subparagraph{2018.0-beta-18}
 
 \begin{itemize}