java rsa pkcs8转pkcs1

<!--pkcs8 -> pkcs1-->
        <dependency>
            <groupId>org.bouncycastle</groupId>
            <artifactId>bcprov-jdk15on</artifactId>
            <version>1.60</version>
        </dependency>

package com.*.api.utils;

import org.bouncycastle.asn1.ASN1Encodable;
import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
import org.bouncycastle.util.io.pem.PemObject;
import org.bouncycastle.util.io.pem.PemWriter;

import javax.crypto.Cipher;
import java.io.IOException;
import java.io.StringWriter;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

/**
 * Java RSA 加密工具类
 */
public class RSAUtils {
    /**
     * 密钥长度 于原文长度对应 以及越长速度越慢
     */
    private final static int KEY_SIZE = 1024;
    /**
     * 用于封装随机产生的公钥与私钥
     */
    private static Map<Integer, String> keyMap = new HashMap<Integer, String>();

    /**
     * 随机生成密钥对
     */
    public static void genKeyPair() throws NoSuchAlgorithmException {
        // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        // 初始化密钥对生成器
        keyPairGen.initialize(KEY_SIZE, new SecureRandom());
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        // 得到私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        // 得到公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        String publicKeyString = Base64.getEncoder().encodeToString(publicKey.getEncoded());
        // 得到私钥字符串
        String privateKeyString = Base64.getEncoder().encodeToString(privateKey.getEncoded());
        // 将公钥和私钥保存到Map
        //0表示公钥
        keyMap.put(0, publicKeyString);
        //1表示私钥
        keyMap.put(1, privateKeyString);
    }

    /**
     * RSA公钥加密
     *
     * @param str       加密字符串
     * @param publicKey 公钥
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public static String encrypt(String str, String publicKey) throws Exception {
        //base64编码的公钥
        byte[] decoded = Base64.getDecoder().decode(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = Base64.getEncoder().encodeToString(cipher.doFinal(str.getBytes("UTF-8")));
        return outStr;
    }

    /**
     * RSA私钥解密
     *
     * @param str        加密字符串
     * @param privateKey 私钥
     * @return 明文
     * @throws Exception 解密过程中的异常信息
     */
    public static String decrypt(String str, String privateKey) throws Exception {
        //64位解码加密后的字符串
        byte[] inputByte = Base64.getDecoder().decode(str);
        //base64编码的私钥
        byte[] decoded = Base64.getDecoder().decode(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }

    /**
     * RSA格式化为pem
     * @param key
     * @return
     */
    public static String formatPemString(String type,byte[] key){
        try {
            PemObject po = new PemObject(type, key);
            StringWriter sw = new StringWriter();
            PemWriter pemWriter = new PemWriter(sw);
            pemWriter.writeObject(po);
            pemWriter.close();
            String pemString = sw.toString();
            return pemString;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * pkcs8 -> pkcs1
     * @param pkcs8
     * @return
     */
    public static byte[] pkcs8Topkcs1(byte[] pkcs8){
        try {
            PrivateKeyInfo pki = PrivateKeyInfo.getInstance(pkcs8);
            ASN1Encodable asn = pki.parsePrivateKey();
            ASN1Primitive primitive = asn.toASN1Primitive();
            byte[] pkcs1 = primitive.getEncoded();
            return pkcs1;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static void main(String[] args) throws Exception {
        genKeyPair();
        System.out.println(keyMap.get(0));
        System.out.println(keyMap.get(1));
//
//        String privateStr = encrypt("友",keyMap.get(0));
//        System.out.println(privateStr);
//        System.out.println(decrypt(privateStr,keyMap.get(1)));
        byte[] privateKey = Base64.getDecoder().decode(keyMap.get(1));
        System.out.println(formatPemString("RSA PRIVATE KEY",pkcs8Topkcs1(privateKey)));
        byte[] publicKey = Base64.getDecoder().decode(keyMap.get(0));
        System.out.println(formatPemString("PUBLIC KEY",publicKey));
    }
}