What is the file size after encryption using AES/CBC/PKCS5Padding in java

Question

I tried to use encryption and decryption when sending files using socket. I use the AES/CBC/PKCS5Padding algorithm and first write the IV and then the file to the stream.

The problem is that the loop does not end when the file is receiving.

I think this is due to the file size and the encrypted file seems to be smaller than the original file, While I give the size of the original file to the receiver. If this hypothesis is correct, is there a way to calculate the size of the encrypted file?

File sender

            SecretKey keySpec = new SecretKeySpec(key, "AES");
            byte[] iv = AES.randomNonce(16);
            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivParameterSpec);

            outputStream = socket.getOutputStream();
            outputStream.write(iv);
            outputStream.flush();
            inputStream = context.getContentResolver().openInputStream(message.getUri());
            cipherOutputStream = new CipherOutputStream(outputStream, cipher);

            long size = message.getSize();
            long written = 0;
            byte[] buffer = new byte[8192];
            int count;
            int percent = 0;
            while (!isStopped && (count = inputStream.read(buffer)) > 0) {
                cipherOutputStream.write(buffer, 0, count);
                written += count;
                int p = (int) (((float) written / (float) size) * 100);
                if (percent != p) {
                    percent = p;
                    if (onProgressListener != null) {
                        onProgressListener.onProgress(percent);
                    }
                }
            }
            cipherOutputStream.flush();
            if (onProgressListener != null) {
                onProgressListener.onEnd(null);
            }

File receiver

            inputStream = socket.getInputStream();
            fileOutputStream = new FileOutputStream(file);
            byte[] iv = new byte[16];
            inputStream.read(iv);

            SecretKey keySpec = new SecretKeySpec(key, "AES");
            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, keySpec, ivParameterSpec);

            cipherInputStream = new CipherInputStream(inputStream, cipher);

            long size = message.getSize();
            long read = size;
            byte[] buffer = new byte[8192];
            int count;
            int percent = 0;
            while (!isStopped && read > 0 && (count = cipherInputStream.read(buffer, 0, (int) Math.min(buffer.length, read))) != -1) {
                fileOutputStream.write(buffer, 0, count);
                read -= count;
                int p = (int) (((float) read / (float) size) * 100);
                if (percent != p) {
                    percent = p;
                    if (onProgressListener != null) {
                        onProgressListener.onProgress(100 - percent);
                    }
                }
            }
            if (onProgressListener != null) {
                onProgressListener.onEnd(Uri.fromFile(file));
            }

Answer 1

I tried to use encryption and decryption when sending files using socket. I use the AES/CBC/PKCS5Padding algorithm and first write the IV and then the file to the stream.

The problem is that the loop does not end when the file is receiving.

I think this is due to the file size and the encrypted file seems to be smaller than the original file, While I give the size of the original file to the receiver. If this hypothesis is correct, is there a way to calculate the size of the encrypted file?

File sender

            SecretKey keySpec = new SecretKeySpec(key, "AES");
            byte[] iv = AES.randomNonce(16);
            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivParameterSpec);

            outputStream = socket.getOutputStream();
            outputStream.write(iv);
            outputStream.flush();
            inputStream = context.getContentResolver().openInputStream(message.getUri());
            cipherOutputStream = new CipherOutputStream(outputStream, cipher);

            long size = message.getSize();
            long written = 0;
            byte[] buffer = new byte[8192];
            int count;
            int percent = 0;
            while (!isStopped && (count = inputStream.read(buffer)) > 0) {
                cipherOutputStream.write(buffer, 0, count);
                written += count;
                int p = (int) (((float) written / (float) size) * 100);
                if (percent != p) {
                    percent = p;
                    if (onProgressListener != null) {
                        onProgressListener.onProgress(percent);
                    }
                }
            }
            cipherOutputStream.flush();
            if (onProgressListener != null) {
                onProgressListener.onEnd(null);
            }

File receiver

            inputStream = socket.getInputStream();
            fileOutputStream = new FileOutputStream(file);
            byte[] iv = new byte[16];
            inputStream.read(iv);

            SecretKey keySpec = new SecretKeySpec(key, "AES");
            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, keySpec, ivParameterSpec);

            cipherInputStream = new CipherInputStream(inputStream, cipher);

            long size = message.getSize();
            long read = size;
            byte[] buffer = new byte[8192];
            int count;
            int percent = 0;
            while (!isStopped && read > 0 && (count = cipherInputStream.read(buffer, 0, (int) Math.min(buffer.length, read))) != -1) {
                fileOutputStream.write(buffer, 0, count);
                read -= count;
                int p = (int) (((float) read / (float) size) * 100);
                if (percent != p) {
                    percent = p;
                    if (onProgressListener != null) {
                        onProgressListener.onProgress(100 - percent);
                    }
                }
            }
            if (onProgressListener != null) {
                onProgressListener.onEnd(Uri.fromFile(file));
            }

Answer 2

I tried to use encryption and decryption when sending files using socket. I use the AES/CBC/PKCS5Padding algorithm and first write the IV and then the file to the stream.

The problem is that the loop does not end when the file is receiving.

I think this is due to the file size and the encrypted file seems to be smaller than the original file, While I give the size of the original file to the receiver. If this hypothesis is correct, is there a way to calculate the size of the encrypted file?

File sender

            SecretKey keySpec = new SecretKeySpec(key, "AES");
            byte[] iv = AES.randomNonce(16);
            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivParameterSpec);

            outputStream = socket.getOutputStream();
            outputStream.write(iv);
            outputStream.flush();
            inputStream = context.getContentResolver().openInputStream(message.getUri());
            cipherOutputStream = new CipherOutputStream(outputStream, cipher);

            long size = message.getSize();
            long written = 0;
            byte[] buffer = new byte[8192];
            int count;
            int percent = 0;
            while (!isStopped && (count = inputStream.read(buffer)) > 0) {
                cipherOutputStream.write(buffer, 0, count);
                written += count;
                int p = (int) (((float) written / (float) size) * 100);
                if (percent != p) {
                    percent = p;
                    if (onProgressListener != null) {
                        onProgressListener.onProgress(percent);
                    }
                }
            }
            cipherOutputStream.flush();
            if (onProgressListener != null) {
                onProgressListener.onEnd(null);
            }

File receiver

            inputStream = socket.getInputStream();
            fileOutputStream = new FileOutputStream(file);
            byte[] iv = new byte[16];
            inputStream.read(iv);

            SecretKey keySpec = new SecretKeySpec(key, "AES");
            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, keySpec, ivParameterSpec);

            cipherInputStream = new CipherInputStream(inputStream, cipher);

            long size = message.getSize();
            long read = size;
            byte[] buffer = new byte[8192];
            int count;
            int percent = 0;
            while (!isStopped && read > 0 && (count = cipherInputStream.read(buffer, 0, (int) Math.min(buffer.length, read))) != -1) {
                fileOutputStream.write(buffer, 0, count);
                read -= count;
                int p = (int) (((float) read / (float) size) * 100);
                if (percent != p) {
                    percent = p;
                    if (onProgressListener != null) {
                        onProgressListener.onProgress(100 - percent);
                    }
                }
            }
            if (onProgressListener != null) {
                onProgressListener.onEnd(Uri.fromFile(file));
            }

Answer 3

Check for this exception. java.io.IOException: javax.crypto.BadPaddingException