java - RSA数据解密错误Java : javax. crypto.BadPaddingException: Decryption error

Question

我在使用 Java 中的 RSA 解密数据(或者也可能是错误的加密)时遇到了问题。我想用字符串中的更多信息加密公钥，然后解密这个公钥并用它加密一些东西(我使用 2048 RSA):

加密:

public void saveExportToFile(String fileName, BigInteger mod, BigInteger exp, String info, PublicKey puk) throws IOException {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    ObjectOutputStream oout = new ObjectOutputStream(new BufferedOutputStream(baos));
    try {
        oout.writeObject(mod);
        oout.writeObject(exp);
        oout.writeChars(info);
        oout.close();
        baos.close();
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, puk);

        FileOutputStream fos = new FileOutputStream(new File(fileName));
        BufferedOutputStream bos = new BufferedOutputStream(fos);

        byte[] data = baos.toByteArray();

        int i = 0;
        byte[] buffer = new byte[128];
        byte[] cipherData = null;
        while (i < data.length) {
            if (i+128 >= data.length) {
                buffer = new byte[data.length - i];
                System.arraycopy(data, i, buffer, 0, data.length - i);
                cipherData = cipher.doFinal(buffer);
                bos.write(cipherData);
            } else {
                System.arraycopy(data, i, buffer, 0, 128);
                cipherData = cipher.doFinal(buffer);
                bos.write(cipherData);
            }
            i += 128;
        }

        bos.close();
    } catch (Exception e) {
        throw new IOException("Unexpected error", e);
    }
}

解密:

public void getDataFromRSA(String sendname, PrivateKey privateKey) {
    try {
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(new File(sendname)));

        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);

        int length = 0;
        int allLength = 0;
        byte[] buffer = new byte[128];
        byte[] bufferAC = null;
        byte[] outData = null;
        byte[] allData = null;
        byte[] tmpData = null;
        while ( (length = bis.read(buffer)) != -1) {
            if (length < 128) {
                bufferAC = new byte[length];
                System.arraycopy(buffer, 0, bufferAC, 0, length);
                outData = cipher.doFinal(bufferAC);
            } else {
                outData = cipher.doFinal(buffer); // HERE IS THE ERROR
            }
            allLength += outData.length;
            tmpData = allData;
            allData = new byte[allLength];
            System.arraycopy(tmpData, 0, allData, 0, tmpData.length);
            System.arraycopy(outData, 0, allData, tmpData.length, outData.length);
        }
    } catch (IOException | NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException | ClassNotFoundException | InvalidKeySpecException e) {
        e.printStackTrace();
    }
}

编辑好吧，看来我对加密的了解并没有我想象的那么多。我只想使用 RSA(如果可能的话)，因为我不需要多次传输信息(信息大小各不相同)。我已经像这样编辑了加密:

int i = 0;
byte[] buffer = new byte[245];
byte[] cipherData = null;
while (i < data.length) {
    if (i+245 >= data.length) {
        buffer = new byte[data.length - i];
        System.arraycopy(data, i, buffer, 0, data.length - i);
    } else {
        System.arraycopy(data, i, buffer, 0, 245);
    }
    cipherData = cipher.update(buffer);
    bos.write(cipherData);
    i += 245;
}
bos.write(cipher.doFinal()); // HERE IS THE ERROR
bos.close();

现在我得到 javax.crypto.IllegalBlockSizeException: Data must not be longer than 245 bytes(尝试了几个较低的缓冲区大小值)。是因为数据长度不是 block 大小的倍数吗？这可以修复吗？感谢您的回答。

Answer 1

首先，您应该使用混合加密，即首先使用对称密码加密数据，然后使用 RSA key 加密随机 secret - 将两者发送到接收方。

其次，您永远不必在循环中为单个消息执行 doFinal。请改用 update 和一个 doFinal。

第三，2048 位是 256 字节。只要您继续尝试解密 128 字节而不是 256 字节，就会出现此异常。通常我使用 2048/Byte.SIZE 代替，它使代码更具可读性并且会避免错误。