secp256k1: Optimize precomp value storage.

This optimizes the storage of the pre-computed byte points used to
accelerate scalar base multiplication to store the data as 32-byte
big-endian integers instead of as a series of little-endian uint32s
which reduces the amount of uncompressed bytes that need to stored by
128KiB.

Further, since the compressed table is stored in the string table of the
binary, it also reduces the size the of final binary by ~92.5KiB.

dcrec/secp256k1/genstatics.go

@@ -14,7 +14,6 @@ package secp256k1
 //   [GECC]: Guide to Elliptic Curve Cryptography (Hankerson, Menezes, Vanstone)
 
 import (
-	"encoding/binary"
 	"math/big"
 )
 
@@ -35,7 +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.
@@ -53,14 +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

@@ -8,7 +8,6 @@ package secp256k1
 import (
 	"compress/zlib"
 	"encoding/base64"
-	"encoding/binary"
 	"io"
 	"strings"
 	"sync"
@@ -69,14 +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