diff options
Diffstat (limited to 'crypto/secp256k1/curve.go')
| -rw-r--r-- | crypto/secp256k1/curve.go | 43 |
1 files changed, 32 insertions, 11 deletions
diff --git a/crypto/secp256k1/curve.go b/crypto/secp256k1/curve.go index 6fdf2be6a..56be235b3 100644 --- a/crypto/secp256k1/curve.go +++ b/crypto/secp256k1/curve.go @@ -1,5 +1,6 @@ // Copyright 2010 The Go Authors. All rights reserved. // Copyright 2011 ThePiachu. All rights reserved. +// Copyright 2015 Jeffrey Wilcke, Felix Lange, Gustav Simonsson. All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are @@ -35,8 +36,6 @@ import ( "crypto/elliptic" "math/big" "unsafe" - - "github.com/ethereum/go-ethereum/common/math" ) /* @@ -45,6 +44,27 @@ extern int secp256k1_ext_scalar_mul(const secp256k1_context* ctx, const unsigned */ import "C" +const ( + // number of bits in a big.Word + wordBits = 32 << (uint64(^big.Word(0)) >> 63) + // number of bytes in a big.Word + wordBytes = wordBits / 8 +) + +// readBits encodes the absolute value of bigint as big-endian bytes. Callers +// must ensure that buf has enough space. If buf is too short the result will +// be incomplete. +func readBits(bigint *big.Int, buf []byte) { + i := len(buf) + for _, d := range bigint.Bits() { + for j := 0; j < wordBytes && i > 0; j++ { + i-- + buf[i] = byte(d) + d >>= 8 + } + } +} + // This code is from https://github.com/ThePiachu/GoBit and implements // several Koblitz elliptic curves over prime fields. // @@ -231,8 +251,9 @@ func (BitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, // Do the multiplication in C, updating point. point := make([]byte, 64) - math.ReadBits(Bx, point[:32]) - math.ReadBits(By, point[32:]) + readBits(Bx, point[:32]) + readBits(By, point[32:]) + pointPtr := (*C.uchar)(unsafe.Pointer(&point[0])) scalarPtr := (*C.uchar)(unsafe.Pointer(&scalar[0])) res := C.secp256k1_ext_scalar_mul(context, pointPtr, scalarPtr) @@ -264,8 +285,8 @@ func (BitCurve *BitCurve) Marshal(x, y *big.Int) []byte { byteLen := (BitCurve.BitSize + 7) >> 3 ret := make([]byte, 1+2*byteLen) ret[0] = 4 // uncompressed point flag - math.ReadBits(x, ret[1:1+byteLen]) - math.ReadBits(y, ret[1+byteLen:]) + readBits(x, ret[1:1+byteLen]) + readBits(y, ret[1+byteLen:]) return ret } @@ -290,11 +311,11 @@ func init() { // See SEC 2 section 2.7.1 // curve parameters taken from: // http://www.secg.org/collateral/sec2_final.pdf - theCurve.P = math.MustParseBig256("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F") - theCurve.N = math.MustParseBig256("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141") - theCurve.B = math.MustParseBig256("0x0000000000000000000000000000000000000000000000000000000000000007") - theCurve.Gx = math.MustParseBig256("0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798") - theCurve.Gy = math.MustParseBig256("0x483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8") + theCurve.P, _ = new(big.Int).SetString("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F", 0) + theCurve.N, _ = new(big.Int).SetString("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141", 0) + theCurve.B, _ = new(big.Int).SetString("0x0000000000000000000000000000000000000000000000000000000000000007", 0) + theCurve.Gx, _ = new(big.Int).SetString("0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798", 0) + theCurve.Gy, _ = new(big.Int).SetString("0x483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8", 0) theCurve.BitSize = 256 } |