rct amount key modified as per luigi1111's recommendations

This allows the key to be not the same for two outputs sent to
the same address (eg, if you pay yourself, and also get change
back). Also remove the key amounts lists and return parameters
since we don't actually generate random ones, so we don't need
to save them as we can recalculate them when needed if we have
the correct keys.

1 files changed, 4 insertions, 14 deletions

diff --git a/src/ringct/rctOps.cpp b/src/ringct/rctOps.cpp
index b8a0d26ad..d54aa667f 100644
--- a/src/ringct/rctOps.cpp
+++ b/src/ringct/rctOps.cpp
@@ -741,28 +741,18 @@ void fe_mul(fe h,const fe f,const fe g)
 
     //Elliptic Curve Diffie Helman: encodes and decodes the amount b and mask a
     // where C= aG + bH
-    void ecdhEncodeFromSharedSecret(ecdhTuple & unmasked, const key & sharedSec1) {
+    void ecdhEncode(ecdhTuple & unmasked, const key & sharedSec) {
+        key sharedSec1 = hash_to_scalar(sharedSec);
         key sharedSec2 = hash_to_scalar(sharedSec1);
         //encode
         sc_add(unmasked.mask.bytes, unmasked.mask.bytes, sharedSec1.bytes);
         sc_add(unmasked.amount.bytes, unmasked.amount.bytes, sharedSec2.bytes);
     }
-    void ecdhEncode(ecdhTuple & unmasked, const key & receiverPk) {
-        key esk;
-        //compute shared secret
-        skpkGen(esk, unmasked.senderPk);
-        key sharedSec1 = hash_to_scalar(scalarmultKey(receiverPk, esk));
-        ecdhEncodeFromSharedSecret(unmasked, sharedSec1);
-    }
-    void ecdhDecodeFromSharedSecret(ecdhTuple & masked, const key & sharedSec1) {
+    void ecdhDecode(ecdhTuple & masked, const key & sharedSec) {
+        key sharedSec1 = hash_to_scalar(sharedSec);
         key sharedSec2 = hash_to_scalar(sharedSec1);
         //decode
         sc_sub(masked.mask.bytes, masked.mask.bytes, sharedSec1.bytes);
         sc_sub(masked.amount.bytes, masked.amount.bytes, sharedSec2.bytes);
     }
-    void ecdhDecode(ecdhTuple & masked, const key & receiverSk) {
-        //compute shared secret
-        key sharedSec1 = hash_to_scalar(scalarmultKey(masked.senderPk, receiverSk));
-        ecdhDecodeFromSharedSecret(masked, sharedSec1);
-    }
 }