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// Copyright 2020 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package bls12381
import (
"errors"
"math/big"
"github.com/ethereum/go-ethereum/common"
)
func bigFromHex(hex string) *big.Int {
return new(big.Int).SetBytes(common.FromHex(hex))
}
// decodeFieldElement expects 64 byte input with zero top 16 bytes,
// returns lower 48 bytes.
func decodeFieldElement(in []byte) ([]byte, error) {
if len(in) != 64 {
return nil, errors.New("invalid field element length")
}
// check top bytes
for i := 0; i < 16; i++ {
if in[i] != byte(0x00) {
return nil, errors.New("invalid field element top bytes")
}
}
out := make([]byte, 48)
copy(out[:], in[16:])
return out, nil
}