Document a subtle point raised by Alex Balducci.

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

protocol/protocol.tex

@@ -2464,7 +2464,9 @@ of their funds, even if they have forgotten everything but the
 Instead, \Zcash enforces that an adversary must choose distinct values
 for each $\NoteAddressRand$, by making use of the fact that all of the
 \nullifiers in \joinSplitDescriptions that appear in a valid \blockchainview
-must be distinct. The \nullifiers are used as input to $\Blake{256}$
+must be distinct. This is true regardless of whether the \nullifiers
+corresponded to real or dummy notes.
+The \nullifiers are used as input to $\Blake{256}$
 to derive a public value $\hSig$ which uniquely identifies the transaction,
 as described in \crossref{hsig}. ($\hSig$ was already used in \Zerocash
 in a way that requires it to be unique in order to maintain
@@ -2662,7 +2664,7 @@ The authors would like to thank everyone with whom they have discussed
 the \Zerocash protocol design; in addition to the inventors, this includes
 Mike Perry, Isis Lovecruft, Leif Ryge, Andrew Miller, Zooko Wilcox,
 Samantha Hulsey, Jack Grigg, Simon Liu, Ariel Gabizon, jl777, Ben Blaxill,
-and no doubt others.
+Alex Balducci, and no doubt others.
 
 The Faerie Gold attack was found by Zooko Wilcox.
 The internal hash collision attack was found by Taylor Hornby.
@@ -2698,7 +2700,8 @@ of $\PRFaddr{}$ was found by Daira Hopwood.
     \item Add \joinSplitTransfers to the Concepts section.
     \item Add a section on Coinbase Transactions.
     \item Add type declarations for functions.
-    \item Add acknowledgements for Jack Grigg, Simon Liu, and jl777.
+    \item Add acknowledgements for Jack Grigg, Simon Liu, Ariel Gabizon, jl777,
+          Ben Blaxill, and Alex Balducci.
     \item Fix a \texttt{Makefile} compatibility problem with the escaping behaviour
           of \texttt{echo}.
     \item Make the date format in references more consistent.