From e181dbe7482424d2658df08e7a0c3cd832839edf Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@z.cash>
Date: Tue, 6 Jun 2017 17:44:17 +1200
Subject: Add comments

---
 src/script/interpreter.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'src/script')

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index 8a121774a0..39e06f4a51 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -174,7 +174,13 @@ bool static IsLowDERSignature(const valtype &vchSig, ScriptError* serror) {
     if (!IsValidSignatureEncoding(vchSig)) {
         return set_error(serror, SCRIPT_ERR_SIG_DER);
     }
+    // https://bitcoin.stackexchange.com/a/12556:
+    //     Also note that inside transaction signatures, an extra hashtype byte
+    //     follows the actual signature data.
     std::vector<unsigned char> vchSigCopy(vchSig.begin(), vchSig.begin() + vchSig.size() - 1);
+    // If the S value is above the order of the curve divided by two, its
+    // complement modulo the order could have been used instead, which is
+    // one byte shorter when encoded correctly.
     if (!CPubKey::CheckLowS(vchSigCopy)) {
         return set_error(serror, SCRIPT_ERR_SIG_HIGH_S);
     }
-- 
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