Use RSA to encrypt and decrypt in Java

rsa_test.java

@Test
public void encrypt_decrypt_jdk_rsa() throws NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, NoSuchPaddingException, BadPaddingException, IllegalBlockSizeException {
    String source = "Hala Madrid!";
    // 1. init secureKey
    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
    keyPairGenerator.initialize(512);
    KeyPair keyPair = keyPairGenerator.generateKeyPair();
    RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
    RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();

    System.out.println("public: " + Base64.encodeBase64String(rsaPublicKey.getEncoded()));
    System.out.println("private: " + Base64.encodeBase64String(rsaPrivateKey.getEncoded()));

    // 2. privateKey encryption, publicKey decryption - encrypt
    PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.ENCRYPT_MODE, privateKey);
    byte[] cipherTextBytes = cipher.doFinal(source.getBytes());
    System.out.println("privateKey encryption: " + Base64.encodeBase64String(cipherTextBytes));

    // 3. privateKey encryption, publicKey decryption - decrypt
    X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
    keyFactory = KeyFactory.getInstance("RSA");
    PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
    cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.DECRYPT_MODE, publicKey);
    byte[] plainTextBytes = cipher.doFinal(cipherTextBytes);
    System.out.println("publicKey decryption: " + new String(plainTextBytes));


    // 4. privateKey decryption, publicKey encryption - encrypt
    x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
    keyFactory = KeyFactory.getInstance("RSA");
    publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
    cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.ENCRYPT_MODE, publicKey);
    cipherTextBytes = cipher.doFinal(source.getBytes());
    System.out.println("publicKey encryption: " + Base64.encodeBase64String(cipherTextBytes));

    // 5. privateKey decryption, publicKey encryption - decrypt
    pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(privateKey.getEncoded());
    keyFactory = KeyFactory.getInstance("RSA");
    privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
    cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.DECRYPT_MODE, privateKey);
    plainTextBytes = cipher.doFinal(cipherTextBytes);
    System.out.println("privateKey decryption: " + new String(plainTextBytes));
}

@Test
public void sign_jdk_rsa() throws NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, SignatureException {
    String source = "Hala Madrid!";
    // 1. init security key
    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
    keyPairGenerator.initialize(512);
    KeyPair keyPair = keyPairGenerator.generateKeyPair();
    RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
    RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();

    // 3. sign
    PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
    Signature signature = Signature.getInstance("MD5withRSA");
    signature.initSign(privateKey);
    signature.update(source.getBytes());
    byte[] signSource = signature.sign();
    System.out.println("jdk rsa sign: " + Hex.encodeHexString(signSource));

    // 3. verify
    X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
    keyFactory = KeyFactory.getInstance("RSA");
    PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
    signature = Signature.getInstance("MD5withRSA");
    signature.initVerify(publicKey);
    signature.update(source.getBytes());
    boolean verify = signature.verify(signSource);
    System.out.println("jdk rsa sign verify: " + verify);
}

@Test
public void sign_jdk_ecdsa() throws NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, SignatureException {
    String source = "Hala Madrid!";

    // 1. init security key
    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("EC");
    keyPairGenerator.initialize(256);
    KeyPair keyPair = keyPairGenerator.generateKeyPair();
    ECPublicKey ecPublicKey = (ECPublicKey) keyPair.getPublic();
    ECPrivateKey ecPrivateKey = (ECPrivateKey) keyPair.getPrivate();

    // 2. sign
    PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(ecPrivateKey.getEncoded());
    KeyFactory keyFactory = KeyFactory.getInstance("EC");
    PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
    Signature signature = Signature.getInstance("SHA1withECDSA");
    signature.initSign(privateKey);
    signature.update(source.getBytes());
    byte[] signBytes = signature.sign();
    System.out.println("jdk ecdsa sign: " + Hex.encodeHexString(signBytes));

    // 3. verify
    X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(ecPublicKey.getEncoded());
    keyFactory = KeyFactory.getInstance("EC");
    PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
    signature = Signature.getInstance("SHA1withECDSA");
    signature.initVerify(publicKey);
    signature.update(source.getBytes());
    boolean verify = signature.verify(signBytes);
    System.out.println("jdk ecdsa verify: " + verify);
}