Please find the below working code:
Working Function code:
package com.test .fn;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;
import java.util.logging.*;
import java.security.SecureRandom;
public class AESEncryptDecrypt {
private static final Logger logger = Logger.getLogger(AESEncryptDecrypt.class.getName());
public static class Input {
public String message;
public String secretKeyBase64;
public String ivBase64;
public String aesMode; // AES/CBC/PKCS5Padding or AES/ECB/PKCS5Padding
public String actionType; //ENCRYPT or DECRYPT
}
public static class Result {
public String message;
public String salt;
public String wechataeskey;
public String executionInfo;
}
public Result handleRequest(Input input) {
logger.log(Level.INFO, "OIC - message:", input.message);
logger.log(Level.INFO, "OIC - secretKeyBase64:", input.secretKeyBase64);
logger.log(Level.INFO, "OIC - ivBase64", input.ivBase64);
logger.log(Level.INFO, "OIC - aesMode:", input.aesMode);
logger.log(Level.INFO, "OIC - actionType:", input.actionType);
Result result = null;
if ("DECRYPT".equals(input.actionType)) {
result = decryptMyMessage(input);
} else if ("ENCRYPT".equals(input.actionType)) {
result = encryptMyMessage(input);
} else {
result = new Result();
result.executionInfo = "ERROR: No proper action found , possible value is ENCRYPT or DECRYPT , recieved value:" + input.actionType;
}
return result;
}
// Generate random 16-byte IV for AES/CBC
public static IvParameterSpec generateIV() {
byte[] iv = new byte[16]; // 128-bit IV
new SecureRandom().nextBytes(iv);
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
return ivParameterSpec;
}
public Result encryptMyMessage(Input input) {
Result result = new Result();
try {
byte[] decodedKey = null;
if (input.secretKeyBase64 == null) {
// Generate 16-digit random numeric string
String keyString = generateRandomDigits(16);
//System.out.println("Generated 16-digit AES key: " + keyString);
// Convert to byte array (each digit becomes 1 byte, 16 bytes total = 128 bits)
result.wechataeskey = keyString;
decodedKey = keyString.getBytes("UTF-8");
} else {
// Decode the base64 encoded string
decodedKey = Base64.getDecoder().decode(input.secretKeyBase64);
}
byte[] messageBytes = input.message.getBytes("UTF-8");
// Create a SecretKeySpec for the AES key
SecretKeySpec secretKeySpec = new SecretKeySpec(decodedKey, "AES");
// Create a Cipher instance for AES
Cipher cipher = Cipher.getInstance(input.aesMode);
if (input.aesMode.contains("CBC")) {
//AES/CBC/PKCS5Padding required IV
IvParameterSpec ivParameterSpec = generateIV();
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
result.salt = Base64.getEncoder().encodeToString(ivParameterSpec.getIV());
} else {
//AES/ECB/PKCS5Padding do not require IV
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
}
// Decrypt the message
byte[] originalBytes = cipher.doFinal(messageBytes);
String encodedString = Base64.getEncoder().encodeToString(originalBytes);
result.message = encodedString;
//String originalMessage = =new String(originalBytes);
result.executionInfo = "SUCCESS";
} catch(Exception e) {
result.executionInfo = e.getMessage();
logger.log(Level.INFO, "Error Details:", e.getMessage());
}
return result;
}
public Result decryptMyMessage(Input input) {
Result result = new Result();
generateIV();
try {
// Decode the base64 encoded string
byte[] decodedKey = Base64.getDecoder().decode(input.secretKeyBase64);
byte[] encryptedBytes = Base64.getDecoder().decode(input.message);
// Create a SecretKeySpec for the AES key
SecretKeySpec secretKeySpec = new SecretKeySpec(decodedKey, "AES");
// Create a Cipher instance for AES
Cipher cipher = Cipher.getInstance(input.aesMode);
if (input.aesMode.contains("CBC")) {
//AES/CBC/PKCS5Padding required IV
byte[] decodedIV = Base64.getDecoder().decode(input.ivBase64);
IvParameterSpec ivParameterSpec = new IvParameterSpec(decodedIV);
cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
} else {
//AES/ECB/PKCS5Padding do not require IV
cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
}
// Decrypt the message
byte[] originalBytes = cipher.doFinal(encryptedBytes);
String encodedString = Base64.getEncoder().encodeToString(originalBytes);
result.message = encodedString;
//String originalMessage = =new String(originalBytes);
result.executionInfo = "SUCCESS";
} catch(Exception e) {
result.executionInfo = e.getMessage();
logger.log(Level.INFO, "Error Details:", e.getMessage());
}
return result;
}
// Wechat, Generate a random string of digits for AES Key
public static String generateRandomDigits(int length) {
SecureRandom random = new SecureRandom();
StringBuilder sb = new StringBuilder(length);
for (int i = 0; i < length; i++) {
sb.append(random.nextInt(10)); // 0-9
}
return sb.toString();
}
public static void main(String[] args) {
AESEncryptDecrypt service = new AESEncryptDecrypt();
Input input = new Input();
input.message = "put encrypted cyper message";
// Base64 for "1234567890123456"
input.secretKeyBase64 = "Put base64 encoded secret key";
input.ivBase64 = "base63 encode salt ot IV";
input.aesMode = "AES/CBC/PKCS5Padding";
input.actionType = "DECRYPT";
Result result = service.handleRequest(input);
// Print output
System.out.println("=== RESULT ===");
System.out.println("Message: " + result.message);
System.out.println("Salt: " + result.salt);
System.out.println("WeChat AES Key: " + result.wechataeskey);
System.out.println("Execution Info: " + result.executionInfo);
}
}
Screenshots:
Test online tool :
https://www.onlinegdb.com/online_java_compiler#
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