package com.security;

import java.math.BigInteger;
import java.security.SecureRandom;

import org.bouncycastle.crypto.generators.ECKeyPairGenerator;
import org.bouncycastle.crypto.params.ECDomainParameters;
import org.bouncycastle.crypto.params.ECKeyGenerationParameters;
import org.bouncycastle.math.ec.ECCurve;
import org.bouncycastle.math.ec.ECFieldElement;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.math.ec.ECFieldElement.Fp;

public class SM2 {
	// 测试参数
	public static final String[] ecc_param = {
	    "8542D69E4C044F18E8B92435BF6FF7DE457283915C45517D722EDB8B08F1DFC3", 
	    "787968B4FA32C3FD2417842E73BBFEFF2F3C848B6831D7E0EC65228B3937E498", 
	    "63E4C6D3B23B0C849CF84241484BFE48F61D59A5B16BA06E6E12D1DA27C5249A", 
	    "8542D69E4C044F18E8B92435BF6FF7DD297720630485628D5AE74EE7C32E79B7", 
	    "421DEBD61B62EAB6746434EBC3CC315E32220B3BADD50BDC4C4E6C147FEDD43D", 
	    "0680512BCBB42C07D47349D2153B70C4E5D7FDFCBFA36EA1A85841B9E46E09A2" 
	};
	
	// 正式参数
	/*public static String[] ecc_param = { 
		"FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF",
		"FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFC",
		"28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E93",
		"FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123",
		"32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7",
		"BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0"
	};*/

	public static SM2 Instance(){
		return new SM2();
	}

	public final BigInteger ecc_p;
	public final BigInteger ecc_a;
	public final BigInteger ecc_b;
	public final BigInteger ecc_n;
	public final BigInteger ecc_gx;
	public final BigInteger ecc_gy;
	public final ECCurve ecc_curve;
	public final ECPoint ecc_point_g;
	public final ECDomainParameters ecc_bc_spec;
	public final ECKeyPairGenerator ecc_key_pair_generator;
	public final ECFieldElement ecc_gx_fieldelement;
	public final ECFieldElement ecc_gy_fieldelement;

	public SM2() {
		this.ecc_p = new BigInteger(ecc_param[0], 16);
		this.ecc_a = new BigInteger(ecc_param[1], 16);
		this.ecc_b = new BigInteger(ecc_param[2], 16);
		this.ecc_n = new BigInteger(ecc_param[3], 16);
		this.ecc_gx = new BigInteger(ecc_param[4], 16);
		this.ecc_gy = new BigInteger(ecc_param[5], 16);

		this.ecc_gx_fieldelement = new Fp(this.ecc_p, this.ecc_gx);
		this.ecc_gy_fieldelement = new Fp(this.ecc_p, this.ecc_gy);

		this.ecc_curve = new ECCurve.Fp(this.ecc_p, this.ecc_a, this.ecc_b);
		this.ecc_point_g = new ECPoint.Fp(this.ecc_curve, this.ecc_gx_fieldelement, this.ecc_gy_fieldelement);

		this.ecc_bc_spec = new ECDomainParameters(this.ecc_curve, this.ecc_point_g, this.ecc_n);

		ECKeyGenerationParameters ecc_ecgenparam;
		ecc_ecgenparam = new ECKeyGenerationParameters(this.ecc_bc_spec, new SecureRandom());

		this.ecc_key_pair_generator = new ECKeyPairGenerator();
		this.ecc_key_pair_generator.init(ecc_ecgenparam);
	}
	
	public byte[] sm2GetZ(byte[] userId, ECPoint userKey){
		SM3Digest sm3 = new SM3Digest();
		
		int len = userId.length * 8;
		sm3.update((byte) (len >> 8 & 0xFF));
		sm3.update((byte) (len & 0xFF));
		sm3.update(userId, 0, userId.length);
		
		byte[] p = Util.byteConvert32Bytes(ecc_a);
		sm3.update(p, 0, p.length);
		
		p = Util.byteConvert32Bytes(ecc_b);
		sm3.update(p, 0, p.length);
		
		p = Util.byteConvert32Bytes(ecc_gx);
		sm3.update(p, 0, p.length);
		
		p = Util.byteConvert32Bytes(ecc_gy);
		sm3.update(p, 0, p.length);
		
		p = Util.byteConvert32Bytes(userKey.getX().toBigInteger());
		sm3.update(p, 0, p.length);
		
		p = Util.byteConvert32Bytes(userKey.getY().toBigInteger());
		sm3.update(p, 0, p.length);
		
		byte[] md = new byte[sm3.getDigestSize()];
		sm3.doFinal(md, 0);
		return md;
	}
	
	public void sm2Sign(byte[] md, BigInteger userD, ECPoint userKey, SM2Result sm2Result) {
		BigInteger e = new BigInteger(1, md);
		BigInteger k = null;
		ECPoint kp = null;
		BigInteger r = null;
		BigInteger s = null;
		do {
			do {
				// 正是环境
				/*AsymmetricCipherKeyPair keypair = ecc_key_pair_generator.generateKeyPair();
				ECPrivateKeyParameters ecpriv = (ECPrivateKeyParameters) keypair.getPrivate();
				ECPublicKeyParameters ecpub = (ECPublicKeyParameters) keypair.getPublic();
				k = ecpriv.getD();
				kp = ecpub.getQ();*/
				
				// 国密规范测试 随机数k
				String kS = "6CB28D99385C175C94F94E934817663FC176D925DD72B727260DBAAE1FB2F96F";
		        k = new BigInteger(kS, 16);
		        kp = this.ecc_point_g.multiply(k);
				
		        System.out.println("计算曲线点X1: " + kp.getX().toBigInteger().toString(16));
				System.out.println("计算曲线点Y1: " + kp.getY().toBigInteger().toString(16));
				System.out.println("");

				// r
				r = e.add(kp.getX().toBigInteger());
				r = r.mod(ecc_n);
			} while (r.equals(BigInteger.ZERO) || r.add(k).equals(ecc_n));

			// (1 + dA)~-1
			BigInteger da_1 = userD.add(BigInteger.ONE);
			da_1 = da_1.modInverse(ecc_n);
			
			// s
			s = r.multiply(userD);
			s = k.subtract(s).mod(ecc_n);
			s = da_1.multiply(s).mod(ecc_n);
		} while (s.equals(BigInteger.ZERO));
		
		sm2Result.r = r;
		sm2Result.s = s;
	}

	public void sm2Verify(byte md[], ECPoint userKey, BigInteger r, BigInteger s, SM2Result sm2Result) {
        sm2Result.R = null;
        BigInteger e = new BigInteger(1, md);
        BigInteger t = r.add(s).mod(ecc_n);
        if(t.equals(BigInteger.ZERO)) {
            return;
        } else {
            ECPoint x1y1 = ecc_point_g.multiply(sm2Result.s);
            System.out.println("计算曲线点X0: " + x1y1.getX().toBigInteger().toString(16));
			System.out.println("计算曲线点Y0: " + x1y1.getY().toBigInteger().toString(16));
			System.out.println("");
			
            x1y1 = x1y1.add(userKey.multiply(t));
            System.out.println("计算曲线点X1: " + x1y1.getX().toBigInteger().toString(16));
			System.out.println("计算曲线点Y1: " + x1y1.getY().toBigInteger().toString(16));
			System.out.println("");
            sm2Result.R = e.add(x1y1.getX().toBigInteger()).mod(ecc_n);
            System.out.println("R: " + sm2Result.R.toString(16));
            return;
        }
    }
}
