[Java] AES(128,192,256)::iv 암복호화

AES 암복호화

AES128 : 키값 16bytes

AES192 : 키값 24bytes

AES256 : 키값 32bytes

 

** ivBytes 값은 16bytes로 랜덤 키값으로 주로 사용한다.

 

 AES256::iv 암호화
 1. "991226" : aes256 encode 후 Base64 encode
 2. 구분자 "::" 추가후 뒤에 iv 값 추가
     ex) 65wUWQtaMSe8PJSBOmTCLA==::mchnuridyvpvrzsy
3. ex 전체 데이터 Base64로 재포장
     최종결과 : R3hvQzJxWTFIc2o5bXQ3RDNpdmpLUT09OjpyZ294em5jcXZvZHpocWdw

import android.util.Base64;
import java.security.spec.AlgorithmParameterSpec;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
 
public class AES256Util {
    //키값 32바이트: AES256 / 24바이트: AES192 / 16바이트: AES128
    private static String secretKey = "HNUJAEBfB9ygAm4wGJZ2XV4qTzFg2XAA";
    private static final String LOWERCASE = "abcdefghijklmnopqrstuvwxyz";
    
    // random iv key 생성
    public static String generateRandomPassword() {
        SecureRandom random = new SecureRandom();
        StringBuilder passwordBuilder = new StringBuilder();

        while (passwordBuilder.length() < 16) {
            int randomIndex = random.nextInt(LOWERCASE.length());
            char randomChar = LOWERCASE.charAt(randomIndex);
            passwordBuilder.append(randomChar);
        }

        return passwordBuilder.toString();
    }
    
    /**
     * AES256::iv 암호화
     * 1. "991226" : aes256 encode 후 Base64 encode
     * 2. 구분자 "::" 추가후 뒤에 iv 값 추가
     *    ex) 65wUWQtaMSe8PJSBOmTCLA==::mchnuridyvpvrzsy
     * 3. 전체 데이터 Base64로 재포장
     *  최종결과 : R3hvQzJxWTFIc2o5bXQ3RDNpdmpLUT09OjpyZ294em5jcXZvZHpocWdw
     * */
    public static String encryptAES256(@NonNull Context context, String str)  {
        String ivString = generateRandomPassword();

        AlgorithmParameterSpec ivSpec = new IvParameterSpec(ivString.getBytes());
        SecretKeySpec newKey = null;
        try {
            newKey = new SecretKeySpec(secretKey.getBytes("UTF-8"), "AES");
        } catch (UnsupportedEncodingException e) {
            DLog.e(new Exception(), e.getMessage());
        }
        Cipher cipher = null;
        try {
            cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, newKey, ivSpec);

        } catch (InvalidKeyException| InvalidAlgorithmParameterException |NoSuchPaddingException | NoSuchAlgorithmException e) {
            DLog.e(new Exception(), e.getMessage());
        }

        String encryptString = "";
        try {
            encryptString = Base64.encodeToString(cipher.doFinal(str.getBytes()), Base64.NO_WRAP)+"::"+ivString;
            encryptString = Base64.encodeToString(encryptString.getBytes(), Base64.NO_WRAP);
        } catch (IllegalBlockSizeException | BadPaddingException e) {
            DLog.e(new Exception(), e.getMessage());
        }
        return encryptString;
    }
 
    /**
     * AES256::iv 복호화
     * */
    public static String decryptAES256(@NonNull Context context, String str)  {
        byte[] textBytes = Base64.decode(str,Base64.DEFAULT);
        String string = new String(textBytes);
        int idx = string.indexOf("::");
        String bodyBase64 = string.substring(0, idx);
        byte[] message = Base64.decode(bodyBase64, Base64.DEFAULT);
        byte[] ivBytes = string.substring(idx+2).getBytes();

        AlgorithmParameterSpec ivSpec = new IvParameterSpec(ivBytes);
        SecretKeySpec newKey = null;
        try {
            newKey = new SecretKeySpec(secretKey.getBytes("UTF-8"), "AES");
        } catch (UnsupportedEncodingException e) {
            DLog.e(new Exception(), e.getMessage());
        }
        Cipher cipher = null;
        try {
            cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, newKey, ivSpec);

        } catch (InvalidKeyException| InvalidAlgorithmParameterException |NoSuchPaddingException | NoSuchAlgorithmException e) {
            DLog.e(new Exception(), e.getMessage());
        }

        String decodeData = null;
        try {
            decodeData = new String(cipher.doFinal(message), "UTF-8");
        } catch (IllegalBlockSizeException | BadPaddingException | UnsupportedEncodingException e) {
            DLog.e(new Exception(), e.getMessage());
        }
        return decodeData;
    }
}

 

 

[사용방법]

String str = "aes256_test";
String encrypt = AES256Util.encryptAES256(this, str);  // "R3hvQzJxWTFIc2o5bXQ3RDNpdmpLUT09OjpyZ294em5jcXZvZHpocWdw"
String decrypt = AES256Util.decryptAES256(this, encrypt); // "aes256_test"