Encryption Algorithm Implementation using Cipher from javax.crypto pa…

…ckage

src/main/java/encryption/EncryptionUtil.java

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+package encryption;
+
+import javax.crypto.*;
+import javax.crypto.spec.IvParameterSpec;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.util.Base64;
+import java.util.Objects;
+
+public class EncryptionUtil {
+    EncryptionUtil encryptionUtil;
+
+    EncryptionUtil getInstance() {
+        synchronized (this) {
+            return Objects.requireNonNullElseGet(encryptionUtil, EncryptionUtil::new);
+        }
+    }
+
+    private EncryptionUtil() {
+    }
+
+    public static String encrypt(String algorithm, String input, SecretKey key, IvParameterSpec iv)
+            throws NoSuchPaddingException, NoSuchAlgorithmException,
+            InvalidAlgorithmParameterException, InvalidKeyException,
+            BadPaddingException, IllegalBlockSizeException {
+        Cipher cipher = Cipher.getInstance(algorithm);
+        cipher.init(Cipher.ENCRYPT_MODE, key, iv);
+//            First applying cipher and then Encoding using Base64 Encryption
+        byte[] cipheredBytes = cipher.doFinal(input.getBytes());
+        return Base64.getEncoder().encodeToString(cipheredBytes);
+    }
+
+    public static String decrypt(String algorithm, String input, SecretKey key, IvParameterSpec iv)
+            throws NoSuchPaddingException, NoSuchAlgorithmException,
+            InvalidAlgorithmParameterException, InvalidKeyException,
+            BadPaddingException, IllegalBlockSizeException {
+        Cipher cipher = Cipher.getInstance(algorithm);
+        cipher.init(Cipher.DECRYPT_MODE, key, iv);
+//          Opposite of encrypt logic. First decoding from Base64 and then deciphering.
+        byte[] decodedBytes = Base64.getDecoder().decode(input.getBytes());
+        byte[] decipheredBytes = cipher.doFinal(decodedBytes);
+        return new String(decipheredBytes);
+    }
+
+    /**
+     * To Generate Initialization Vector (IV). It is a pseudo-random value
+     * and has the same size as the block that is encrypted.
+     **/
+    public static IvParameterSpec generateIv() {
+        byte[] iv = new byte[16];
+        new SecureRandom().nextBytes(iv);
+        return new IvParameterSpec(iv);
+    }
+
+
+    public static SecretKey generateKey(int n) throws NoSuchAlgorithmException {
+        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
+        keyGenerator.init(n);
+        return keyGenerator.generateKey();
+    }
+
+
+}

src/test/java/encryption/EncryptionUtilTest.java

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+package encryption;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import javax.crypto.BadPaddingException;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.NoSuchPaddingException;
+import javax.crypto.SecretKey;
+import javax.crypto.spec.IvParameterSpec;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+
+public class EncryptionUtilTest {
+
+    @Test
+    void givenString_whenEncrypt_thenSuccess() throws NoSuchAlgorithmException,
+            IllegalBlockSizeException, InvalidKeyException, BadPaddingException,
+            InvalidAlgorithmParameterException, NoSuchPaddingException {
+        String input = "Vamsi";
+        SecretKey key = EncryptionUtil.generateKey(256);
+        IvParameterSpec ivParameterSpec = EncryptionUtil.generateIv();
+        String algorithm = "AES/CBC/PKCS5Padding";
+        String cipherText = EncryptionUtil.encrypt(algorithm, input, key, ivParameterSpec);
+        String decipheredText = EncryptionUtil.decrypt(algorithm, cipherText, key, ivParameterSpec);
+        assertEquals(input, decipheredText);
+    }
+}