Generate publickey with der format public key and report an error

Recent projects use RSA Encrypt and decrypt public and private key pairs , Encounter will der Format public key converted to PublicKey Error reporting , The exception information is as follows ：

cn.hutool.crypto.CryptoException: InvalidKeySpecException: encoded key spec not recognized: unknown object in getInstance: org.bouncycastle.asn1.ASN1Integer
        at cn.hutool.crypto.KeyUtil.generatePublicKey(KeyUtil.java:355)
        at cn.hutool.crypto.KeyUtil.generatePublicKey(KeyUtil.java:335)
        at com.unionpay.trust.crypto.util.HsmUtilTest.testGenerateRsaAndPubKeyEncrypt(HsmUtilTest.java:95)
        at com.unionpay.trust.crypto.util.HsmUtilTest.main(HsmUtilTest.java:61)
Caused by: java.security.spec.InvalidKeySpecException: encoded key spec not recognized: unknown object in getInstance: org.bouncycastle.asn1.ASN1Integer
        at org.bouncycastle.jcajce.provider.asymmetric.util.BaseKeyFactorySpi.engineGeneratePublic(Unknown Source)
        at org.bouncycastle.jcajce.provider.asymmetric.rsa.KeyFactorySpi.engineGeneratePublic(Unknown Source)
        at java.security.KeyFactory.generatePublic(KeyFactory.java:328)
        at cn.hutool.crypto.KeyUtil.generatePublicKey(KeyUtil.java:353)

Use der Format public key converted to PublicKey This is done as follows ：

// It cannot be generated normally publickey
            // PublicKey publicKey = KeyUtil.generatePublicKey("RSA", Forms.hexStringToByte(publicKeyDerHex));
            // PublicKey publicKey = KeyUtil.generatePublicKey("RSA/ECB/PKCS1Padding", Forms.hexStringToByte(publicKeyDerHex));
            // PublicKey publicKey = KeyUtil.generatePublicKey("RSA/ECB/NoPadding", Forms.hexStringToByte(publicKeyDerHex));
            // PublicKey publicKey = KeyUtil.generatePublicKey("RSA/None/NoPadding", Forms.hexStringToByte(publicKeyDerHex));
            // PublicKey publicKey = KeyUtil.generateRSAPublicKey(Forms.hexStringToByte(publicKeyDerHex));

 None of the above methods can be generated normally PublicKey, The errors reported are all the above abnormal information 

The reasons for the error are as follows ：

Generated by encryptor RSA The public key is ANS.1 Coded , The use of conversion here requires that ANS.1 Code to X509 code , The specific conversion method is as follows ：

/**
     * RSA  Public key   format conversion  ANS1 turn X509
     * @param encodedKey    Public key 
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static byte[] ansOneToX509(byte[] encodedKey) throws NoSuchAlgorithmException, InvalidKeySpecException {

        //  call ASN1Sequence, Yes ASN1 Of RSADER Code to decode 
        ASN1Sequence asn1 = ASN1Sequence.getInstance(encodedKey);
        Enumeration<?> e = asn1.getObjects();
        BigInteger modulus = ASN1Integer.getInstance(e.nextElement()).getPositiveValue();
        BigInteger publicExponent = ASN1Integer.getInstance(e.nextElement()).getPositiveValue();

        //  Reconstruct a x509 object , And get the encoded data 
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey pubkey = keyFactory.generatePublic(new RSAPublicKeySpec(modulus, publicExponent));
        byte[] x509Encoded = pubkey.getEncoded();
        return x509Encoded;
    }

After the conversion , Let's talk about it again der Format conversion to PublicKey It's normal .