/*
Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package sm2

import (
	"crypto/elliptic"
	"math/big"
	"sync"
)

var initonce sync.Once
var p256Sm2Params *elliptic.CurveParams

// 取自elliptic的p256.go文件，修改曲线参数为sm2
// See FIPS 186-3, section D.2.3
func initP256Sm2() {
	p256Sm2Params = &elliptic.CurveParams{Name: "SM2-P-256"} // 注明为SM2
	//SM2椭	椭 圆 曲 线 公 钥 密 码 算 法 推 荐 曲 线 参 数
	p256Sm2Params.P, _ = new(big.Int).SetString("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF", 16)
	p256Sm2Params.N, _ = new(big.Int).SetString("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123", 16)
	p256Sm2Params.B, _ = new(big.Int).SetString("28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E93", 16)
	p256Sm2Params.Gx, _ = new(big.Int).SetString("32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7", 16)
	p256Sm2Params.Gy, _ = new(big.Int).SetString("BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0", 16)
	p256Sm2Params.BitSize = 256
}

func P256Sm2() elliptic.Curve {
	initonce.Do(initP256Sm2)
	return p256Sm2Params
}