New "Halfway RingCT" outputs for coinbase transactions

When RingCT is enabled, outputs from coinbase transactions
are created as a single output, and stored as RingCT output,
with a fake mask. Their amount is not hidden on the blockchain
itself, but they are then able to be used as fake inputs in
a RingCT ring. Since the output amounts are hidden, their
"dustiness" is not an obstacle anymore to mixing, and this
makes the coinbase transactions a lot smaller, as well as
helping the TXO set to grow more slowly.

Also add a new "Null" type of rct signature, which decreases
the size required when no signatures are to be stored, as
in a coinbase tx.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/ringct/rctTypes.h b/src/ringct/rctTypes.h
index da2e3808c..58e08b0f7 100644
--- a/src/ringct/rctTypes.h
+++ b/src/ringct/rctTypes.h
@@ -174,8 +174,9 @@ namespace rct {
     // outPk contains public keypairs which are destinations (P, C),
     //  P = address, C = commitment to amount
     enum {
-      RCTTypeFull = 0,
-      RCTTypeSimple = 1,
+      RCTTypeNull = 0,
+      RCTTypeFull = 1,
+      RCTTypeSimple = 2,
     };
     struct rctSigBase {
         uint8_t type;
@@ -189,6 +190,8 @@ namespace rct {
 
         BEGIN_SERIALIZE()
             FIELD(type)
+            if (type == RCTTypeNull)
+              return true;
             // FIELD(message) - not serialized, it can be reconstructed
             // FIELD(mixRing) - not serialized, it can be reconstructed
             if (type == RCTTypeSimple)
@@ -224,6 +227,8 @@ namespace rct {
 
         BEGIN_SERIALIZE_OBJECT()
             FIELDS(*static_cast<rctSigBase *>(this))
+            if (type == RCTTypeNull)
+              return true;
             FIELDS(p);
         END_SERIALIZE()
     };