以 16 字节为单位处理数据

Question

我正在 java 中构建一个加密工具。我得到了这个方法：

public byte[] blockEncrypt(byte[] b) {
//...
}

它以一个 16 字节的数组作为参数。但我不希望用户自己拆分字节，所以我创建了这个方法：

public byte[] encrypt(final byte[] plain) {

    int remainder = plain.length % blockSize();
    // I create the final array of size modulo blockSize
    byte[] encrypted = new byte[plain.length - remainder + (remainder == 0 ? 0 : blockSize())];
    // Here the array is splitted 
    byte[][] splitted = CryptoUtil.splitBytes(plain, blockSize());

    // I pad the last block if the argument is not modulo blockSize (with '=')
    if (plain.length % blockSize() != 0) {
        byte[] last = new byte[blockSize()];
        CryptoUtil.fill(last, (byte) 0x3D);
        System.arraycopy(splitted[splitted.length - 1], 0, last, 0, splitted[splitted.length - 1].length);
        splitted[splitted.length - 1] = last;
    }

    for (int i = 0; i < splitted.length; i++) {
        System.arraycopy(blockEncrypt(splitted[i], 0), 0, encrypted, i * blockSize(), blockSize());
    }
    return encrypted;
}

这段代码根本不起作用（而且很乱）。我根本不关心它是如何实现的，我只想处理参数中的所有数据，每 16 个字节 16 个字节。有没有人有这个方法？最后一个非完整块的大小应调整为 16（通过添加空字节或任何内容）。预先感谢您的帮助。

Answer 1

我不知道这是否过于复杂，但这是我想出的：

public List<byte[]> splitArray(byte[] array, int blockSize) {
    if (array.length < blockSize) {
        // shortcut if array is too small, will pad end with 0s
        return Arrays.asList(Arrays.copyOf(array, blockSize));
    } else if (array.length == blockSize) {
        // shortcut if array length is already blockSize
        return Arrays.asList(array);
    }
    List<byte[]> list = new ArrayList<>();
    int from = 0;
    int to;
    while ((to = from + blockSize) <= array.length) {
        // keep adding to list while array has another blockSize range of elements
        list.add(Arrays.copyOfRange(array, from, to));
        from = to;
    }
    if (from != array.length) {
        // array did not divide into blockSize evenly, fill last block
        // with remaining elements. Pads end with 0s
        byte[] leftOver = new byte[blockSize];
        System.arraycopy(array, from, leftOver, 0, array.length - from);
        list.add(leftOver);
    }
    return list;
}

我将 return 类型从 byte[][] 更改为 List<byte[]>（我发现 List 更易于使用）。

以 16 字节为单位处理数据

Process data in blocks of 16 bytes

java

arrays

byte

padding