java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: IOException : DerInputStream.getLength(): lengthTag=111, too big.

RSA用私钥签名的时候发现报错，删除以下内容即可

 -----BEGIN PRIVATE KEY-----

-----END PRIVATE KEY-----

import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
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.HashMap;
import java.util.Map;

/**
 * @author :cza
 * @date :2021/4/14 9:52
 * @description :
 * @modyified By:
 */
public class RSAEncrypt {
    private static Map<Integer, String> keyMap = new HashMap<Integer, String>();  //用于封装随机产生的公钥与私钥
    public static void main(String[] args) throws Exception {
        //生成公钥和私钥
        genKeyPair();
        //加密字符串
        String message = "df723820";
        System.out.println("随机生成的公钥为:" + keyMap.get(0));
        System.out.println("随机生成的私钥为:" + keyMap.get(1));
        String messageEn = encrypt(message,keyMap.get(0));
        System.out.println(message + "	加密后的字符串为:" + messageEn);
        String messageDe = decrypt(messageEn,keyMap.get(1));
        System.out.println("还原后的字符串为:" + messageDe);
    }

    /**
     * 随机生成密钥对
     * @throws NoSuchAlgorithmException
     */
    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，密钥大小为96-1024位
        keyPairGen.initialize(1024,new SecureRandom());
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公钥
        String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
        // 得到私钥字符串
        String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
        // 将公钥和私钥保存到Map
        keyMap.put(0,publicKeyString);  //0表示公钥
        keyMap.put(1,privateKeyString);  //1表示私钥
    }
    /**
     * 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.decodeBase64(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.encodeBase64String(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 铭文
     * @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.decodeBase64(str.getBytes("UTF-8"));
        //base64编码的私钥
        byte[] decoded = Base64.decodeBase64(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;
    }

    /**
     * 签名
     *
     * @param data 待签名数据
     * @param privateKey 私钥
     * @return 签名
     */
    public static String sign(String data, PrivateKey privateKey) throws Exception {
        byte[] keyBytes = privateKey.getEncoded();
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PrivateKey key = keyFactory.generatePrivate(keySpec);
        Signature signature = Signature.getInstance("MD5withRSA");
        signature.initSign(key);
        signature.update(data.getBytes());
        return new String(Base64.encodeBase64(signature.sign()));
    }

    /**
     * rsa签名
     *
     * @param content
     *            待签名的字符串
     * @param privateKey
     *            rsa私钥字符串
     * @param charset
     *            字符编码
     * @return 签名结果
     * @throws Exception
     *             签名失败则抛出异常
     */
    public static String sign(String content, String privateKey) throws Exception {

        //base64编码的私钥
        byte[] decoded = Base64.decodeBase64(privateKey);
        try {
            //RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));

            // 取得私钥
            byte[] pri_key_bytes = Base64.decodeBase64(privateKey);
            PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(pri_key_bytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            // 生成私钥
            PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);

            return sign(content,priKey);
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }
    }

    /**
     * 验签
     *
     * @param srcData 原始字符串
     * @param publicKey 公钥
     * @param sign 签名
     * @return 是否验签通过
     */
    public static boolean verify(String srcData, PublicKey publicKey, String sign) throws Exception {
        byte[] keyBytes = publicKey.getEncoded();
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey key = keyFactory.generatePublic(keySpec);
        Signature signature = Signature.getInstance("MD5withRSA");
        signature.initVerify(key);
        signature.update(srcData.getBytes());
        return signature.verify(Base64.decodeBase64(sign.getBytes()));
    }

    /**
     * 验签
     *
     * @param srcData 原始字符串
     * @param publicKey 公钥
     * @param sign 签名
     * @return 是否验签通过
     */
    public static boolean verify(String srcData, String publicKey, String sign) throws Exception {
        byte[] publicBytes = Base64.decodeBase64(publicKey);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey pubKey = keyFactory.generatePublic(keySpec);
        return verify(srcData,pubKey,sign);
    }