AES 加密，解密文件中有多余的垃圾字符

The problem is when i decrypt the encrypted log i got some weird content in it, i also got the encrypted content, but there are some extra characters, see below.

Android 应用日志部分:

public class FileLogger {

//file and folder name
public static String LOG_FILE_NAME = "my_log.txt";
public static String LOG_FOLDER_NAME = "my_log_folder";

static SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd_HH-mm-ss_SSS");

//My secret key, 16 bytes = 128 bit
static byte[] key = {1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6};

//Appends to a log file, using encryption
public static void appendToLog(Context context, Object msg) {

    String msgStr;
    String timestamp = "t:" + formatter.format(new java.util.Date());

    msgStr = msg + "|" + timestamp + "
";

    File sdcard = Environment.getExternalStorageDirectory();
    File dir = new File(sdcard.getAbsolutePath() + "/" + LOG_FOLDER_NAME);
    if (!dir.exists()) {
        dir.mkdir();
    }

    File encryptedFile = new File(dir, LOG_FILE_NAME);

    try {
        
        //Encryption using my key above defined
        Key secretKey = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);

        byte[] outputBytes = cipher.doFinal(msgStr.getBytes());

        //Writing to the file using append mode
        FileOutputStream outputStream = new FileOutputStream(encryptedFile, true);
        outputStream.write(outputBytes);
        outputStream.close();
        
        
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        e.printStackTrace();
    } catch (IllegalBlockSizeException e) {
        e.printStackTrace();
    } catch (BadPaddingException e) {
        e.printStackTrace();
    } catch (InvalidKeyException e) {
        e.printStackTrace();
    }

}

}

这是解密JAVA程序:

public class Main {

    

//output file name after decryption
private static String decryptedFileName;
//input encrypted file
private static String fileSource;
//a prefix tag for output file name
private static String outputFilePrefix = "decrypted_";
//My key for decryption, its the same as in the encrypter program.
static byte[] key = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6 };

//Decrypting function
public static void decrypt(byte[] key, File inputFile, File outputFile) throws Exception {
    try {

        Key secretKey = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, secretKey);

        FileInputStream inputStream = new FileInputStream(inputFile);
        byte[] inputBytes = new byte[(int) inputFile.length()];
        inputStream.read(inputBytes);

        byte[] outputBytes = cipher.doFinal(inputBytes);

        FileOutputStream outputStream = new FileOutputStream(outputFile, true);
        outputStream.write(outputBytes);

        inputStream.close();
        outputStream.close();

    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

//first argument is the intput file source
public static void main(String[] args) {

    if (args.length != 1) {
        System.out.println("Add log file name as a parameter.");

    } else {
        fileSource = args[0];

        try {
            File sourceFile = new File(fileSource);
            if (sourceFile.exists()) {
                
                //Decrption
                decryptedFileName = outputFilePrefix + sourceFile.getName();
                File decryptedFile = new File(decryptedFileName);
                decrypt(key, sourceFile, decryptedFile);
            } else {
                System.out.println("Log file not found: " + fileSource);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println("Decryption done, output file: " + decryptedFileName);
    }

}

}

输出解密后的日志(用notepad++打开):

T这是有效内容，但您也可以看到额外的 thrash 字符.如果我使用默认的 windows 文本编辑器打开，我也会得到 thrash 字符，但不同.

private static SecretKey key = generateAESkey();
private static String cipherString = "AES/CBC/PKCS5Padding";

public static void main(String[] args) throws Exception {
    ByteArrayOutputStream log = new ByteArrayOutputStream();
    appendToLog("Test1", log);
    appendToLog("Test2 is longer", log);
    appendToLog("Test3 is multiple of block size!", log);
    appendToLog("Test4 is shorter.", log);

    byte[] encLog = log.toByteArray();

    List<String> logs = decryptLog(new ByteArrayInputStream(encLog));

    for(String logLine : logs) {
        System.out.println(logLine);
    }
}

private static SecretKey generateAESkey() {
    try {
        return KeyGenerator.getInstance("AES").generateKey();
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return null;
}

private static byte[] generateIV() {
    SecureRandom random = new SecureRandom();
    byte[] iv = new byte[16];
    random.nextBytes(iv);
    return iv;
}

public static void appendToLog(String s, OutputStream os) throws Exception {
    Cipher cipher = Cipher.getInstance(cipherString);
    byte[] iv = generateIV();
    cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(iv));
    byte[] data = cipher.doFinal(s.getBytes("UTF-8"));
    os.write(data.length);
    os.write(iv);
    os.write(data);
}

public static List<String> decryptLog(InputStream is) throws Exception{
    ArrayList<String> logs = new ArrayList<String>();
    while(is.available() > 0) {
        int len = is.read();
        byte[] encLogLine = new byte[len];
        byte[] iv = new byte[16];
        is.read(iv);
        is.read(encLogLine);

        Cipher cipher = Cipher.getInstance(cipherString);
        cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
        byte[] data = cipher.doFinal(encLogLine);
        logs.add(new String(data, "UTF-8"));
    }
    return logs;
}