RSAService.java

package ftn.security.minikms.service;

import ftn.security.minikms.entity.KeyMaterial;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

public class RSAService implements ICryptoService {
    public KeyMaterial generateKey() throws NoSuchAlgorithmException {
        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
        generator.initialize(3072);
        var pair = generator.generateKeyPair();
        return KeyMaterial.of(pair);
    }
    public String encrypt(String input, KeyMaterial key) throws InvalidKeyException,
            IllegalBlockSizeException, BadPaddingException,
            NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeySpecException {
        Cipher encryptCipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");

        KeyFactory factory = KeyFactory.getInstance("RSA");
        PublicKey publicKey = factory.generatePublic(new X509EncodedKeySpec(key.getPublicKey()));

        encryptCipher.init(Cipher.ENCRYPT_MODE, publicKey);

        byte[] secretMessageBytes = input.getBytes(StandardCharsets.UTF_8);
        byte[] encryptedMessageBytes = encryptCipher.doFinal(secretMessageBytes);
        return Base64.getEncoder().encodeToString(encryptedMessageBytes);
    }

    public String decrypt(String encrypted, KeyMaterial key) throws NoSuchPaddingException, NoSuchAlgorithmException,
            InvalidKeyException, IllegalBlockSizeException, BadPaddingException, InvalidKeySpecException {
        Cipher decryptCipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");

        KeyFactory factory = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = factory.generatePrivate(new PKCS8EncodedKeySpec(key.getKey()));

        decryptCipher.init(Cipher.DECRYPT_MODE, privateKey);

        byte[] encryptedBytes = Base64.getDecoder().decode(encrypted);
        byte[] decryptedMessageBytes = decryptCipher.doFinal(encryptedBytes);

        return new String(decryptedMessageBytes, StandardCharsets.UTF_8);
    }
}