Java Android AES解密结果如果只有长字符串，将被截断

Question

我正在尝试用AES（“AES/CBC/PKCS7Padding”）用密码加密和解密纯文本。
由KeyGenerator制作secretKey，并用它加密/解密。这一开始效果很好。

但是，如果纯文本是一个大字符串（如183244个字符），则解密其中的一部分，而不是全部。

“part of it”表示
如果纯文本为“abcdefghijklmn”，则解密文本为“abcdefgh”
（这是一个示例。实际上，只有字符太长时才会出现这种情况）

        // get key from Android kyestore
        SecretKey secretKey = (SecretKey)mKeyStore.getKey(KEY_ALIAS, null);

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);

        IvParameterSpec ivParams = cipher.getParameters().getParameterSpec(IvParameterSpec.class);

        //
        // Encrypt
        //
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        CipherOutputStream cipherOutputStream = new CipherOutputStream(outputStream, cipher);
        cipherOutputStream.write(plainString.getBytes("UTF-8"));
        cipherOutputStream.close();

        String encryptedString = Base64.encodeToString(outputStream.toByteArray(), Base64.DEFAULT);

        //
        // Decrypt
        //
        Cipher decryptCipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
        decryptCipher.init(Cipher.DECRYPT_MODE, secretKey, ivParams);

        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(Base64.decode(encryptedString, Base64.DEFAULT));
        CipherInputStream cipherInputStream = new CipherInputStream(byteArrayInputStream, decryptCipher);
        outputStream = new ByteArrayOutputStream();

        int b;
        while ((b = cipherInputStream.read()) != -1) {
            outputStream.write(b);
        }
        outputStream.close();

        String decryptedString =  outputStream.toString("UTF-8");

        //
        // results. decrypted string is part of source string and short.
        //
        int sourceStringLength = plainString.length(); // is 183244;
        int decryptedStringLength = decryptedString.length()); // is UNEXPECTED 68553;

你能告诉我修好这件事的要点吗？

我检查了加密/解密的字节数。

加密输出字节：“OutputStream.TobyteArray（）.Length”为68560
解密输入字节：“Base64.Decode（encryptedString,Base64.Default).Length”也为68560

  cipherOutputStream.write(plainString.getBytes("UTF-8"));
  cipherOutputStream.close();

        // NOTE: workaround. too bit bytes doesn't writted correctly.
        byte[] bytes = plainString.getBytes("UTF-8");

        int oneBulkSize = 1024;// temp value for proof of concept. might be bigger one.
        int numOfBulk = (bytes.length / oneBulkSize);

        for (int i = 0; i < numOfBulk; i++) {
            cipherOutputStream.write(bytes, oneBulkSize * i, oneBulkSize);
        }

        if ((bytes.length % oneBulkSize) != 0) {
            cipherOutputStream.write(bytes, oneBulkSize * numOfBulk, bytes.length % oneBulkSize);
        }
        cipherOutputStream.close();

解决了问题。

Answer 1

AES没有数据长度限制。加密数据的长度应与输入相同，再加上最多16字节的填充长度。

在加密循环中添加一些调试代码，并验证正在读取整个输入。也许加密流和解密流一样需要一个循环。

另一种可能是183244是UTF-16编码的字节大小，但您读取的是UTF-8，大多数UTF-16字符可以是一个UTF-8字节。

  cipherOutputStream.write(plainString.getBytes("UTF-8"));
  cipherOutputStream.close();

        // NOTE: workaround. too bit bytes doesn't writted correctly.
        byte[] bytes = plainString.getBytes("UTF-8");

        int oneBulkSize = 1024;// temp value for proof of concept. might be bigger one.
        int numOfBulk = (bytes.length / oneBulkSize);

        for (int i = 0; i < numOfBulk; i++) {
            cipherOutputStream.write(bytes, oneBulkSize * i, oneBulkSize);
        }

        if ((bytes.length % oneBulkSize) != 0) {
            cipherOutputStream.write(bytes, oneBulkSize * numOfBulk, bytes.length % oneBulkSize);
        }
        cipherOutputStream.close();