国密SM2,SM3,SM4在BC上的实现（二）

本节讲的SM2的实现，这个其实是可以参照RSA来写，都是非对称加密。

我们通过KeyPairGenerator.getInstance("SM2").generateKeyPair();来获取密钥对，最后调用的就是KeyPairGenSpi的generateKeyPair()，仿照RSA中的KeyPairGeneratorSpi来写，

package org.gk.gm.SM2.spi;

import org.bouncycastle.asn1.x9.X9ECParameters;
import org.bouncycastle.jcajce.provider.asymmetric.ec.KeyPairGeneratorSpi.EC;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.SecureRandom;
import java.security.interfaces.ECPrivateKey;
import java.security.interfaces.ECPublicKey;
import java.security.spec.AlgorithmParameterSpec;

import org.bouncycastle.jce.spec.ECParameterSpec;
import org.gk.gm.SM2.util.ECUtil;
import org.gk.gm.provider.SMProvider;

public class KeyPairGenSpi extends EC {
   
    public KeyPairGenSpi() {
        try {

            X9ECParameters x9 = ECUtil.getNamedCurveByName("SM2");
            ECParameterSpec parameterSpec =  new ECParameterSpec(x9.getCurve(), x9.getG(), x9.getN());
            super.initialize(parameterSpec, (SecureRandom)null);
        } catch (InvalidAlgorithmParameterException var2) {
            var2.printStackTrace();
        }

    }

    public KeyPair generateKeyPair() {
        KeyPair keyPair = super.generateKeyPair();

        try {
            SM2PrivateKey e = new SM2PrivateKey((ECPrivateKey)keyPair.getPrivate(), SMProvider.CONFIGURATION);
            SM2PublicKey publicKey = new SM2PublicKey((ECPublicKey)keyPair.getPublic(), SMProvider.CONFIGURATION);
            return new KeyPair(publicKey, e);
        } catch (InvalidKeyException var4) {
            return null;
        }
    }

    public void initialize(AlgorithmParameterSpec params) throws InvalidAlgorithmParameterException {
        super.initialize((AlgorithmParameterSpec)null, (SecureRandom)null);
    }

    public void initialize(int keySize) {
        try {
            super.initialize((AlgorithmParameterSpec)null, (SecureRandom)null);
        } catch (InvalidAlgorithmParameterException var3) {
            ;
        }

    }

    public void initialize(AlgorithmParameterSpec params, SecureRandom random) throws InvalidAlgorithmParameterException {
        super.initialize((AlgorithmParameterSpec)null, random);
    }

    public void initialize(int keySize, SecureRandom random) {
        try {
            super.initialize((AlgorithmParameterSpec)null, random);
        } catch (InvalidAlgorithmParameterException var4) {
            ;
        }

    }
}

我们这里继承EC（EC也是继承KeyPairGenerator的），其中构造方法就是对SM2进行初始化，SM2PublicKey，SM2PrivateKey这个都是自定义的，这个可以随个人的爱好，只是加解密的时候，对应的变一下就可以了，这里公钥genEncode返回的是512bit（128byte），私钥256bit（64byte）。
好了，再看加密，加密CipherSpi这个类跟RSA的差不多。

public class CipherSpi extends BaseCipherSpi {
   
    private int opMode;
    private AsymmetricKeyParameter keyParam = null;
    private SM2Cipher sm2Cipher = null;
    private ECPoint c1 = null;
    private ByteArrayOutputStream bout = null;

    public CipherSpi() {
    }

    protected void engineInit(int opmode, Key key, SecureRandom random) throws InvalidKeyException {
        if(opmode != 1 && opmode != 2) {
            throw new InvalidKeyException("Only supports ENCRYPT_MODE|DECRYPT_MODE.");
        } else if(key == null || !(key instanceof ECPublicKey) && !(key instanceof ECPrivateKey)) {
            throw new InvalidKeyException("No useful Key.");
        } else if(opmode == 2 && key instanceof ECPublicKey) {
            throw new InvalidKeyException("DECRYPT_MODE needs a Private Key.");
        } else {
            if(this.sm2Cipher == null) {
                this.sm2Cipher = new SM2Cipher();
            }

            this.keyParam = key instanceof ECPublicKey?ECUtil.generatePublicKeyParameter((ECPublicKey)key):ECUtil.generatePrivateKeyParameter((ECPrivateKey)key);
            if(opmode == 1) {
                ECPoint q = null;
                if(