secp256k1: Optimize precomp value storage.

dcrec/secp256k1/genprecomps.go

@@ -1,5 +1,5 @@
 // Copyright 2015 The btcsuite developers
-// Copyright (c) 2015-2021 The Decred developers
+// Copyright (c) 2015-2022 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -44,7 +44,7 @@ func main() {
 	base64.StdEncoding.Encode(encoded, compressed.Bytes())
 
 	fmt.Fprintln(fi, "// Copyright (c) 2015 The btcsuite developers")
-	fmt.Fprintln(fi, "// Copyright (c) 2015-2021 The Decred developers")
+	fmt.Fprintln(fi, "// Copyright (c) 2015-2022 The Decred developers")
 	fmt.Fprintln(fi, "// Use of this source code is governed by an ISC")
 	fmt.Fprintln(fi, "// license that can be found in the LICENSE file.")
 	fmt.Fprintln(fi)
@@ -54,6 +54,13 @@ func main() {
 	fmt.Fprintln(fi, "// DO NOT EDIT")
 	fmt.Fprintln(fi)
 	fmt.Fprintf(fi, "var compressedBytePoints = %q\n", string(encoded))
+	fmt.Fprintln(fi)
+	fmt.Fprintln(fi, "// Set accessor to a real function.")
+	fmt.Fprintln(fi, "func init() {")
+	fmt.Fprintln(fi, "	compressedBytePointsFn = func() string {")
+	fmt.Fprintln(fi, "		return compressedBytePoints")
+	fmt.Fprintln(fi, "	}")
+	fmt.Fprintln(fi, "}")
 
 	a1, b1, a2, b2 := secp256k1.EndomorphismVectors()
 	fmt.Println("The following values are the computed linearly " +

dcrec/secp256k1/genstatics.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2014-2015 The btcsuite developers
-// Copyright (c) 2015-2021 The Decred developers
+// Copyright (c) 2015-2022 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -14,14 +14,9 @@ package secp256k1
 //   [GECC]: Guide to Elliptic Curve Cryptography (Hankerson, Menezes, Vanstone)
 
 import (
-	"encoding/binary"
 	"math/big"
 )
 
-// compressedBytePoints are dummy points used so the code which generates the
-// real values can compile.
-var compressedBytePoints = ""
-
 // SerializedBytePoints returns a serialized byte slice which contains all of
 // the possible points per 8-bit window.  This is used to when generating
 // compressedbytepoints.go.
@@ -39,7 +34,7 @@ func SerializedBytePoints() []byte {
 
 	// Separate the bits into byte-sized windows.
 	curveByteSize := curveParams.BitSize / 8
-	serialized := make([]byte, curveByteSize*256*2*10*4)
+	serialized := make([]byte, curveByteSize*256*2*32)
 	offset := 0
 	for byteNum := 0; byteNum < curveByteSize; byteNum++ {
 		// Grab the 8 bits that make up this byte from doubling points.
@@ -57,14 +52,10 @@ func SerializedBytePoints() []byte {
 			}
 			point.ToAffine()
 
-			for i := 0; i < len(point.X.n); i++ {
-				binary.LittleEndian.PutUint32(serialized[offset:], point.X.n[i])
-				offset += 4
-			}
-			for i := 0; i < len(point.Y.n); i++ {
-				binary.LittleEndian.PutUint32(serialized[offset:], point.Y.n[i])
-				offset += 4
-			}
+			point.X.PutBytesUnchecked(serialized[offset:])
+			offset += 32
+			point.Y.PutBytesUnchecked(serialized[offset:])
+			offset += 32
 		}
 	}
 

dcrec/secp256k1/loadprecomputed.go

@@ -1,5 +1,5 @@
 // Copyright 2015 The btcsuite developers
-// Copyright (c) 2015-2021 The Decred developers
+// Copyright (c) 2015-2022 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -8,7 +8,6 @@ package secp256k1
 import (
 	"compress/zlib"
 	"encoding/base64"
-	"encoding/binary"
 	"io"
 	"strings"
 	"sync"
@@ -20,6 +19,11 @@ import (
 // accelerating scalar base multiplication.
 type bytePointTable [32][256][2]FieldVal
 
+// compressedBytePointsFn is set to a real function by the code generation to
+// return the compressed pre-computed values for accelerating scalar base
+// multiplication.
+var compressedBytePointsFn func() string
+
 // s256BytePoints houses pre-computed values used to accelerate scalar base
 // multiplication such that they are only loaded on first use.
 var s256BytePoints = func() func() *bytePointTable {
@@ -38,10 +42,10 @@ var s256BytePoints = func() func() *bytePointTable {
 	var data *bytePointTable
 	mustLoadBytePoints := func() {
 		// There will be no byte points to load when generating them.
-		bp := compressedBytePoints
-		if len(bp) == 0 {
+		if compressedBytePointsFn == nil {
 			return
 		}
+		bp := compressedBytePointsFn()
 
 		// Decompress the pre-computed table used to accelerate scalar base
 		// multiplication.
@@ -64,14 +68,10 @@ var s256BytePoints = func() func() *bytePointTable {
 			for i := 0; i < len(bytePoints[byteNum]); i++ {
 				px := &bytePoints[byteNum][i][0]
 				py := &bytePoints[byteNum][i][1]
-				for i := 0; i < len(px.n); i++ {
-					px.n[i] = binary.LittleEndian.Uint32(serialized[offset:])
-					offset += 4
-				}
-				for i := 0; i < len(py.n); i++ {
-					py.n[i] = binary.LittleEndian.Uint32(serialized[offset:])
-					offset += 4
-				}
+				px.SetByteSlice(serialized[offset:])
+				offset += 32
+				py.SetByteSlice(serialized[offset:])
+				offset += 32
 			}
 		}
 		data = &bytePoints