壓縮是在加密之后發生的嗎？

Question

在審查加密方案時，我遇到了以下代碼：

    @Override
    public OutputStream encrypt(OutputStream outputStream) throws Exception {

        // generate the IV for encryption
        final byte[] encryptionIV = KeyFileUtil.randomBytes(16);
        outputStream.write(encryptionIV);

        // now create the encryption cipher
        final Cipher cipher = Cipher.getInstance(ENCRYPTION_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, getKey(), new GCMParameterSpec(128, encryptionIV));

        // The CipherOutputStream shouldn't close the underlying stream
        outputStream = new FilterOutputStream(outputStream) {
            @Override
            public void close() throws IOException {
                // Do nothing
            }
        };
        final CipherOutputStream cos = new CipherOutputStream(outputStream, cipher);

        if (useZip) {
            final ZipOutputStream zipOutputStream = new ZipOutputStream(cos) {
                @Override
                public void finish() throws IOException {
                    super.finish();
                    def.end();
                }

                @Override
                public void flush() {
                    // Do nothing.
                }

                @Override
                public void close() throws IOException {
                    try {
                        super.flush();
                    } catch (final IOException exception) {
                        // Continue and try to close.
                    }
                    super.close();
                }
            };
            zipOutputStream.putNextEntry(new ZipEntry("ResourceContents"));
            return zipOutputStream;
        }
        return cos;
    }

據我所知，流的順序是數據首先被加密，然后（無用地）被壓縮。 這是正確的還是我誤解了 OutputStreams 上的排序方式？

謝謝

Answer 1

是的，您誤解（或閱讀）了訂購的運作方式。

在new ZipOutputStream(cos)處， CipherOutputStream被ZOS包裝，因此數據首先被壓縮，然后傳遞給包裝的 stream，它將加密數據，然后將其傳遞給下一個包裝的 stream，依此類推。

最外層stream先拿到go處的數據，如果開啟壓縮，則return zipOutputStream; 被稱為，zipstream 是最外層的 stream。它是FilterOutputStream的慣用用法。