Correct some uses of r_J that should have been r_S or q.

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

protocol/protocol.tex

@@ -2165,7 +2165,7 @@ appropriate length given by the type of $a$.
 
 \notsprout{
 $\ssqrt{a}$, where $a \typecolon \GF{q}$, means the positive
-(i.e.\ in the range $\range{0}{\hfrac{\ParamJ{r}-1}{2}}$)
+(i.e.\ in the range $\range{0}{\hfrac{q-1}{2}}$)
 square root of $a$ in $\GF{q}$. It is only used in cases where the
 square root must exist.
 
@@ -4930,7 +4930,7 @@ For details of the form and encoding of \spendStatement proofs, see \crossref{gr
 
         The $\ValueCommitOutput$ and $\SpendAuthSigPublic$ types also represent points, i.e. $\GroupJ$.
   \item In the Merkle path validity check, each \merkleLayer does \emph{not} check that its
-        input bit sequence is a canonical encoding (in $\range{0}{\ParamJ{r}-1}$) of the integer
+        input bit sequence is a canonical encoding (in $\range{0}{\ParamS{r}-1}$) of the integer
         from the previous \merkleLayer.
   \item It is \emph{not} checked in the \spendStatement that $\AuthSignRandomizedPublic$ is not of
         small order. However, this \emph{is} checked outside the \spendStatement, as specified in
@@ -6130,10 +6130,10 @@ $(D \typecolon \byteseq{8}$, $M \typecolon \bitseq{\PosInt})$ such that $\Select
 The latter can only be the affine-Edwards $u$-coordinate of a point in $\strut\GroupJ$.
 We show that there are no points in $\GroupJ$ with affine-Edwards $u$-coordinate $1$.
 Suppose for a contradiction that $(u, \varv) \in \GroupJ$ for $u = 1$ and some
-$\varv \typecolon \GF{\ParamJ{r}}$. By writing the curve equation as
+$\varv \typecolon \GF{\ParamS{r}}$. By writing the curve equation as
 $\varv^2 = (1 - \ParamJ{a} \smult u^2) / (1 - \ParamJ{d} \smult u^2)$, and noting that
 $1 - \ParamJ{d} \smult u^2 \neq 0$, we have $\varv^2 = (1 - \ParamJ{a}) / (1 - \ParamJ{d})$.
-The right-hand-side is a nonsquare in $\GF{\ParamJ{r}}$, so there are no solutions for $\varv$
+The right-hand-side is a nonsquare in $\GF{\ParamS{r}}$, so there are no solutions for $\varv$
 (contradiction).
 \end{proof}
 } %sapling
@@ -9776,6 +9776,7 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
 \begin{itemize}
     \item No changes to \Sprout.
 \sapling{
+    \item Correct some uses of $\ParamJ{r}$ that should have been $\ParamS{r}$ or $q$.
     \item Minor changes to avoid clashing notation, affecting extractors
           $\Extractor{\Adversary}$, Edwards curves $\Edwards{a,d}$, and Montgomery curves
           $\Montgomery{A,B}$.
@@ -10848,7 +10849,7 @@ the wrong answer. We must ensure that these cases do not arise.
 We will need the theorem below about $y$-coordinates of points on
 Montgomery curves.
 
-\fact{$\ParamM{A}^2 - 4$ is a nonsquare in $\GF{\ParamJ{r}}$.}
+\fact{$\ParamM{A}^2 - 4$ is a nonsquare in $\GF{\ParamS{r}}$.}
 
 \begin{theorem} \label{thmmontynotzero}
 Let $P = (x, y)$ be a point other than $(0, 0)$ on a Montgomery curve $\Montgomery{A,B}$