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88 lines
2.3 KiB
88 lines
2.3 KiB
package babyjub
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import (
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"bytes"
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"encoding/hex"
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"fmt"
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"math/big"
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"strings"
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"github.com/dchest/blake512" // I have personally reviewed that this module doesn't do anything suspicious
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)
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// SwapEndianness swaps the endianness of the value encoded in xs. If xs is
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// Big-Endian, the result will be Little-Endian and viceversa.
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func SwapEndianness(xs []byte) []byte {
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ys := make([]byte, len(xs))
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for i, b := range xs {
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ys[len(xs)-1-i] = b
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}
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return ys
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}
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// BigIntLEBytes encodes a big.Int into an array in Little-Endian.
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func BigIntLEBytes(v *big.Int) [32]byte {
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le := SwapEndianness(v.Bytes())
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res := [32]byte{}
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copy(res[:], le)
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return res
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}
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// SetBigIntFromLEBytes sets the value of a big.Int from a Little-Endian
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// encoded value.
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func SetBigIntFromLEBytes(v *big.Int, leBuf []byte) *big.Int {
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beBuf := SwapEndianness(leBuf)
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return v.SetBytes(beBuf)
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}
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// Blake512 performs the blake-512 hash over the buffer m. Note that this is
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// the original blake from the SHA3 competition and not the new blake2 version.
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func Blake512(m []byte) []byte {
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h := blake512.New()
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h.Write(m[:])
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return h.Sum(nil)
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}
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// Hex is a byte slice type that can be marshalled and unmarshaled in hex
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type Hex []byte
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// MarshalText encodes buf as hex
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func (buf Hex) MarshalText() ([]byte, error) {
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return []byte(hex.EncodeToString(buf)), nil
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}
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// String encodes buf as hex
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func (buf Hex) String() string {
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return hex.EncodeToString(buf)
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}
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// HexEncode encodes an array of bytes into a string in hex.
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func HexEncode(bs []byte) string {
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return fmt.Sprintf("0x%s", hex.EncodeToString(bs))
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}
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// HexDecode decodes a hex string into an array of bytes.
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func HexDecode(h string) ([]byte, error) {
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if strings.HasPrefix(h, "0x") {
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h = h[2:]
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}
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return hex.DecodeString(h)
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}
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// HexDecodeInto decodes a hex string into an array of bytes (dst), verifying
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// that the decoded array has the same length as dst.
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func HexDecodeInto(dst []byte, h []byte) error {
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if bytes.HasPrefix(h, []byte("0x")) {
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h = h[2:]
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}
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if len(h)/2 != len(dst) {
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return fmt.Errorf("expected %v bytes in hex string, got %v", len(dst), len(h)/2)
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}
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n, err := hex.Decode(dst, h)
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if err != nil {
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return err
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} else if n != len(dst) {
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return fmt.Errorf("expected %v bytes when decoding hex string, got %v", len(dst), n)
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}
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return nil
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}
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