Encryption with RSA using Java in Spring Framework.

CipherUtility.java

package com.jsgao.bean;

import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.annotation.PostConstruct;  

import org.springframework.stereotype.Component;

@Component
public class CipherUtility {

	private static KeyPairGenerator keyPairGenerator = null;
	
	private final SecureRandom random = new SecureRandom();
	
	public KeyPair getKeyPair() {
		return keyPairGenerator.genKeyPair();
	}
	
	public String encrypt(String content, Key pubKey) throws NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
		byte[] contentBytes = content.getBytes();
		Cipher cipher = Cipher.getInstance("RSA");
	   	cipher.init(Cipher.ENCRYPT_MODE, pubKey);
	    	byte[] cipherContent = cipher.doFinal(contentBytes);
	    	String encoded = Base64.getEncoder().encodeToString(cipherContent);
	    	return encoded;
	}
	
	public String decrypt(String cipherContent, Key privKey) throws NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
		Cipher cipher = Cipher.getInstance("RSA");
	    	cipher.init(Cipher.DECRYPT_MODE, privKey);
	    	byte[] cipherContentBytes = Base64.getDecoder().decode(cipherContent.getBytes());
	    	byte[] decryptedContent = cipher.doFinal(cipherContentBytes);
	    	String decoded = new String(decryptedContent);
	    	return decoded;
	}
	
	public String encodeKey(Key key) {
		byte[] keyBytes = key.getEncoded();
		String encodedKeyStr = Base64.getEncoder().encodeToString(keyBytes);
		return encodedKeyStr;
	}
	
	public PublicKey decodePublicKey(String keyStr) throws NoSuchAlgorithmException, InvalidKeySpecException {
		byte[] keyBytes = Base64.getDecoder().decode(keyStr);
		X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance("RSA");
		PublicKey key = keyFactory.generatePublic(spec);
		return key;
	}
	
	public PrivateKey decodePrivateKey(String keyStr) throws NoSuchAlgorithmException, InvalidKeySpecException {
		byte[] keyBytes = Base64.getDecoder().decode(keyStr);
		PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance("RSA");
		PrivateKey key = keyFactory.generatePrivate(keySpec);
		return key;
	}
	
	@PostConstruct
	private void init() {
		try {
			if(keyPairGenerator == null) keyPairGenerator = KeyPairGenerator.getInstance("RSA");
			keyPairGenerator.initialize(1024, random);
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
  
}

CipherUtilityTest.java

package com.jsgao.bean;

import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;

import javax.crypto.BadPaddingException;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import com.jsgao.Application;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = Application.class)
public class CipherUtilityTest {
	
	@Autowired
	private CipherUtility cipherUtility;

	@Test
	public void cipherTest() {
		
		String plain = "Happy day!";
		
		// Initialization of key pair for encryption and decryption.
		KeyPair keyPair = cipherUtility.getKeyPair();
		
		try {
			// Get public key from the key pair.
			PublicKey pubKey = keyPair.getPublic();
			
			// Get private key from the key pair.
			PrivateKey privKey = keyPair.getPrivate();
			
			// Try to encode public key as a string.
			String pubKeyStr = cipherUtility.encodeKey(pubKey);
			// Assertion of 'pubKey' and the public key decoded by 'pubKeyStr'.
			Assert.assertEquals(pubKey, cipherUtility.decodePublicKey(pubKeyStr));
			
			// Try to encode private key as a string.
			String privKeyStr = cipherUtility.encodeKey(privKey);
			// Assertion of 'privKey' and the private key decoded by 'privKeyStr'.
			Assert.assertEquals(privKey, cipherUtility.decodePrivateKey(privKeyStr));
			
			// Encrypt plain as a cipher.
			String cipherContent = cipherUtility.encrypt(plain, pubKey);
			// Decrypt cipher to original plain.
			String decryptResult = cipherUtility.decrypt(cipherContent, privKey);
			// Assertion of 'plain' and 'decryptResult'.
			Assert.assertEquals(plain, decryptResult);
		} catch (InvalidKeyException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchProviderException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchPaddingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalBlockSizeException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (BadPaddingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvalidKeySpecException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}

}