1// Copyright 2020 The go-ethereum Authors 2// This file is part of the go-ethereum library. 3// 4// The go-ethereum library is free software: you can redistribute it and/or modify 5// it under the terms of the GNU Lesser General Public License as published by 6// the Free Software Foundation, either version 3 of the License, or 7// (at your option) any later version. 8// 9// The go-ethereum library is distributed in the hope that it will be useful, 10// but WITHOUT ANY WARRANTY; without even the implied warranty of 11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12// GNU Lesser General Public License for more details. 13// 14// You should have received a copy of the GNU Lesser General Public License 15// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. 16 17package bls12381 18 19import ( 20 "errors" 21 "math/big" 22 23 "github.com/ethereum/go-ethereum/common" 24) 25 26func bigFromHex(hex string) *big.Int { 27 return new(big.Int).SetBytes(common.FromHex(hex)) 28} 29 30// decodeFieldElement expects 64 byte input with zero top 16 bytes, 31// returns lower 48 bytes. 32func decodeFieldElement(in []byte) ([]byte, error) { 33 if len(in) != 64 { 34 return nil, errors.New("invalid field element length") 35 } 36 // check top bytes 37 for i := 0; i < 16; i++ { 38 if in[i] != byte(0x00) { 39 return nil, errors.New("invalid field element top bytes") 40 } 41 } 42 out := make([]byte, 48) 43 copy(out[:], in[16:]) 44 return out, nil 45} 46