From 0d9242e5dc37bee97c7f61c6e106d9b45bdd24aa Mon Sep 17 00:00:00 2001
From: Antioch Peverell <30642645+antiochp@users.noreply.github.com>
Date: Sun, 13 May 2018 13:59:27 -0400
Subject: [PATCH] refactor on master, pass in offset as blinding_factor (#1064)

---
 chain/src/txhashset.rs       | 11 ++---------
 core/src/core/block.rs       |  9 +--------
 core/src/core/mod.rs         | 15 ++++++++++-----
 core/src/core/transaction.rs |  9 +--------
 4 files changed, 14 insertions(+), 30 deletions(-)

diff --git a/chain/src/txhashset.rs b/chain/src/txhashset.rs
index 94a2d842f..531cefc5b 100644
--- a/chain/src/txhashset.rs
+++ b/chain/src/txhashset.rs
@@ -22,7 +22,6 @@ use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::time::Instant;
 
-use util::static_secp_instance;
 use util::secp::pedersen::{Commitment, RangeProof};
 
 use core::consensus::REWARD;
@@ -665,20 +664,14 @@ impl<'a> Extension<'a> {
 	pub fn validate_sums(&self, header: &BlockHeader) -> Result<((Commitment, Commitment)), Error> {
 		let now = Instant::now();
 
-		let offset = {
-			let secp = static_secp_instance();
-			let secp = secp.lock().unwrap();
-			let key = header.total_kernel_offset.secret_key(&secp)?;
-			secp.commit(0, key)?
-		};
-
 		// Treat the total "supply" as one huge overage that needs to be accounted for.
 		// If we have a supply of 6,000 grin then we should
 		// have a corresponding 6,000 grin in unspent outputs.
 		let supply = ((header.height * REWARD) as i64).checked_neg().unwrap_or(0);
 		let output_sum = self.sum_commitments(supply, None)?;
 
-		let (kernel_sum, kernel_sum_plus_offset) = self.sum_kernel_excesses(&offset, None)?;
+		let (kernel_sum, kernel_sum_plus_offset) =
+			self.sum_kernel_excesses(&header.total_kernel_offset, None)?;
 
 		if output_sum != kernel_sum_plus_offset {
 			return Err(Error::InvalidTxHashSet(
diff --git a/core/src/core/block.rs b/core/src/core/block.rs
index c0a7dc742..8ef89fcc4 100644
--- a/core/src/core/block.rs
+++ b/core/src/core/block.rs
@@ -722,16 +722,9 @@ impl Block {
 		let overage = (REWARD as i64).checked_neg().unwrap_or(0);
 		let io_sum = self.sum_commitments(overage, Some(prev_output_sum))?;
 
-		let offset = {
-			let secp = static_secp_instance();
-			let secp = secp.lock().unwrap();
-			let key = self.header.total_kernel_offset.secret_key(&secp)?;
-			secp.commit(0, key)?
-		};
-
 		// Sum the kernel excesses accounting for the kernel offset.
 		let (kernel_sum, kernel_sum_plus_offset) =
-			self.sum_kernel_excesses(&offset, Some(prev_kernel_sum))?;
+			self.sum_kernel_excesses(&self.header.total_kernel_offset, Some(prev_kernel_sum))?;
 
 		if io_sum != kernel_sum_plus_offset {
 			return Err(Error::KernelSumMismatch);
diff --git a/core/src/core/mod.rs b/core/src/core/mod.rs
index 5467b82e7..d1befe4fc 100644
--- a/core/src/core/mod.rs
+++ b/core/src/core/mod.rs
@@ -37,6 +37,8 @@ pub use self::id::ShortId;
 use core::hash::Hashed;
 use ser::{Error, Readable, Reader, Writeable, Writer};
 use global;
+use keychain;
+use keychain::BlindingFactor;
 
 /// Implemented by types that hold inputs and outputs (and kernels)
 /// containing Pedersen commitments.
@@ -46,9 +48,9 @@ pub trait Committed {
 	/// Gather the kernel excesses and sum them.
 	fn sum_kernel_excesses(
 		&self,
-		offset: &Commitment,
+		offset: &BlindingFactor,
 		extra_excess: Option<&Commitment>,
-	) -> Result<(Commitment, Commitment), secp::Error> {
+	) -> Result<(Commitment, Commitment), keychain::Error> {
 		let zero_commit = secp_static::commit_to_zero_value();
 
 		// then gather the kernel excess commitments
@@ -68,13 +70,16 @@ pub trait Committed {
 			secp.commit_sum(kernel_commits, vec![])?
 		};
 
-		// sum the commitments along with the specified offset
+		// sum the commitments along with the
+		// commit to zero built from the offset
 		let kernel_sum_plus_offset = {
 			let secp = static_secp_instance();
 			let secp = secp.lock().unwrap();
 			let mut commits = vec![kernel_sum];
-			if *offset != zero_commit {
-				commits.push(*offset);
+			if *offset != BlindingFactor::zero() {
+				let key = offset.secret_key(&secp)?;
+				let offset_commit = secp.commit(0, key)?;
+				commits.push(offset_commit);
 			}
 			secp.commit_sum(commits, vec![])?
 		};
diff --git a/core/src/core/transaction.rs b/core/src/core/transaction.rs
index 6c575bd74..4e6fffc7e 100644
--- a/core/src/core/transaction.rs
+++ b/core/src/core/transaction.rs
@@ -418,15 +418,8 @@ impl Transaction {
 		let overage = self.fee() as i64;
 		let io_sum = self.sum_commitments(overage, None)?;
 
-		let offset = {
-			let secp = static_secp_instance();
-			let secp = secp.lock().unwrap();
-			let key = self.offset.secret_key(&secp)?;
-			secp.commit(0, key)?
-		};
-
 		// Sum the kernel excesses accounting for the kernel offset.
-		let (_, kernel_sum) = self.sum_kernel_excesses(&offset, None)?;
+		let (_, kernel_sum) = self.sum_kernel_excesses(&self.offset, None)?;
 
 		// sum of kernel commitments (including the offset) must match
 		// the sum of input/output commitments (minus fee)