AES

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.util.Base64;

public class AESManager {

    // 16바이트(128비트) 키와 IV 설정 (실제 사용 시 외부에서 관리 권장)
    private static final String KEY = "1234567890123456";
    private static final String IV = "abcdefghijklmnop";
    private static final String ALGO = "AES/CBC/PKCS5Padding";

    public static void main(String[] args) {
        if (args.length < 2) {
            System.out.println("사용법:");
            System.out.println("  암호화: java AESManager enc \"평문\"");
            System.out.println("  복호화: java AESManager dec \"암호문(Base64)\"");
            return;
        }

        String mode = args[0];    // enc 또는 dec
        String input = args[1];   // 대상 문자열

        try {
            if ("enc".equalsIgnoreCase(mode)) {
                String encrypted = encrypt(input);
                System.out.println("암호화 결과 (Base64): " + encrypted);
            } else if ("dec".equalsIgnoreCase(mode)) {
                String decrypted = decrypt(input);
                System.out.println("복호화 결과: " + decrypted);
            } else {
                System.out.println("알 수 없는 모드입니다. 'enc' 또는 'dec'를 사용하세요.");
            }
        } catch (Exception e) {
            System.err.println("오류 발생: " + e.getMessage());
        }
    }

    // --- 암호화 메소드 ---
    public static String encrypt(String plainText) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGO);
        SecretKeySpec keySpec = new SecretKeySpec(KEY.getBytes(StandardCharsets.UTF_8), "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(IV.getBytes(StandardCharsets.UTF_8));

        cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
        
        byte[] encryptedBytes = cipher.doFinal(plainText.getBytes(StandardCharsets.UTF_8));
        return Base64.getEncoder().encodeToString(encryptedBytes);
    }

    // --- 복호화 메소드 ---
    public static String decrypt(String cipherText) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGO);
        SecretKeySpec keySpec = new SecretKeySpec(KEY.getBytes(StandardCharsets.UTF_8), "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(IV.getBytes(StandardCharsets.UTF_8));

        cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);

        byte[] decodedBytes = Base64.getDecoder().decode(cipherText);
        byte[] decryptedBytes = cipher.doFinal(decodedBytes);
        return new String(decryptedBytes, StandardCharsets.UTF_8);
    }
}