Question

通过cryptojs加密文件会使文件大小增加近30％。这在使用C＃中的AESManaged类解密文件时导致问题。如何将加密对象保存为文件而不增加太多的大小？

JS中的文件加密：

function esp() {
        selectedFiles = document.getElementById("MainContent_file1");
        var sfile = selectedFiles.files[0];
        var read = new FileReader();
        read.onload = function (e) {
            var encrypted = CryptoJS.AES.encrypt(read.result, '123456');
            var ct = encrypted.toString();
            debugger;
            $.ajax({
                async: 'true',
                url: "http://localhost:51936/WebService1.asmx/FileUpload",
                method: "POST",
                processData: 'false',
                headers: {
                    'content-type': "application/json",
                    'cache-control': "no-cache"
                },
                data: JSON.stringify({ 'folderPath': folderPath, 'uploadData': ct, 'fileName': sfile.name + '.encrypted' }),
                success: function (response) {
                    console.log(response);
                },
                error: function (xhr, textStatus, error) {
                    console.log(xhr.statusText);
                }
            });
        }
        read.readAsDataURL(sfile);
    }

将加密对象保存为文件的Web服务：

[WebMethod]
    public bool FileUpload(string folderPath, string uploadData, string fileName)
    {
        //NOTE: A CODE SCAN TOOL is showing a PATH TRAVERSAL ERROR. a folderPath can be retrieve from DATABASE for remove the error but would affect the performance which is not advisable.
        bool returnValue = false;
        try
        {
            byte[] byteUploadFile = Convert.FromBase64String(uploadData);
            BinaryWriter binWriter = new BinaryWriter(File.Open(Path.Combine(folderPath, fileName), FileMode.Create, FileAccess.ReadWrite));
            binWriter.Write(byteUploadFile);
            binWriter.Close();
            returnValue = true;
        }
        catch (Exception ex)
        {
            returnValue = false;
        }
        return returnValue;
    }

Answer 1

我将加密字符串（base64）保存为文件的方式是正确的。但是，为了正确解密并从解密的字符串中生成原始文件，需要进行一些剥离。请参阅下文，了解我如何从加密文件中获取解密字符串并将其另存为原始文件。

Mywebservice.Mywebservice dts = new Mywebservice.Mywebservice();
            using (var rijAlg = new RijndaelManaged())
            {
                rijAlg.Key = keybytes;
                rijAlg.IV = iv;
                var decryptor = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV);
                using (var msDecrypt = new MemoryStream(cipherText))
                {
                    using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (var srDecrypt = new StreamReader(csDecrypt))
                        {
                            plaintext = srDecrypt.ReadToEnd();
                        }
                    }
                }
            }
            plaintext = plaintext.Substring(23); //This is the part to strip. The first
            //23 chars are the mime type of the file. Remove that and just save the string data.
            string name = filename.Replace(".encrypted", "");
            dts.FileUpload(folderPath, plaintext, name); //call the same webservice used for saving encrypted object.
        }

CryptoJs文件加密大大增加了文件大小

1 个答案: