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Posted 16 Apr 2005

Encrypt and decrypt DataSets to XML files

, 23 Apr 2005
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This class lib allows encrypting DataSets to XML files and reading them back. A Win Form app is included as a showcase.


XML is an easy, portable way to save DataSets within the .NET Framework. All methods to handle the XML are contained within .NET, so the end user will not need proprietary data handling software or server to read in the data.

I recently needed the ability to save encrypted DataSets to track a student's learning progress. Obviously, the XML format was too accessible to save this sort of information which needed to be kept from tampering, so I needed encryption, which comes standard with .NET. However, I was still facing a few challenges:

  1. I wanted to be able to accomplish all encryption and decryption with just a few calls to a special "crypto" class library.
  2. While decrypting a file in .NET is very easy, I wanted to avoid having temporary unencrypted files written to disk in the process.
  3. The start of every XML file is quite standard, so it can potentially be used to "guess" the encryption key and crack the code.
  4. Finally, I needed a mechanism to recognize encrypted files so the DataSet would not load erroneous data.

I set out to develop a class library (XMLEncryptor) to encrypt and decrypt DataSets using a username and password. The challenges above were handled as follows:

The XMLEncryptor class is instantiated using two strings, a user name and password. The constructor creates the encryption key and initialization vector, as well as a 16-byte signature.

The signature, which is written as a file header without encryption, is used by the XMLEncryptor to identify files as having been encrypted using its methods. Also, the signature serves as a mask for to push the standard XML header to the 17th byte in the file, which should offer some level of protection against "guessing" the XML header (see 3 above).

The XMLEncryptor exposes two public functions, one for reading in the encrypted XML file and one for writing the DataSet back to a file:

  • public DataSet ReadEncryptedXML(string fileName)
  • public void WriteEncryptedXML(DataSet dataset, string encFileName)

The ReadEncryptedXML function will return a DataSet if all goes as intended. The encrypted XML data is decrypted into a MemoryStream, which is subsequently used to load a DataSet which can then be returned to the caller without having intermediary files written to disk. If an error is encountered during reading, decryption etc., the ReadEncryptedXML function returns null.

The WriteEncryptedXML function takes the DataSet and writes it to a file using the same encryption key and IV as was used for the decryption. Once again, no temporary files are involved.

A typical use of the XMLEncryptor would be as follows:

   XMLEncryptor XMLenc = new XMLEncryptor("myname", "mypassword");
   // Load encrypted file into DataSet
   DataSet myDataSet = XMLenc.ReadEncryptedXML("myfile.enc");
   // test for successful read
   if (myDataSet == null)
      // Do something
   // write back the dataset
   XMLEnc.WriteEncryptedXML(myDataSet, "myfile.enc");

Limitations of the application are:

  1. The handling of the username and password is left up to the parent application.
  2. Files of more than 2 GB cannot be handled. However, since the process involves in-memory handling of data, practical size limits may be smaller.

That's all!



This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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Comments and Discussions

GeneralMy vote of 1 Pin
BhagwatiPal1-Apr-11 0:54
memberBhagwatiPal1-Apr-11 0:54 
GeneralRe: My vote of 1 Pin
d347hm4n18-Nov-11 0:38
memberd347hm4n18-Nov-11 0:38 
GeneralMore elegant way Pin
super-e-20-Sep-09 23:00
membersuper-e-20-Sep-09 23:00 
Generalbug fix Pin
Ronchen7777-Jul-09 4:28
memberRonchen7777-Jul-09 4:28 
GeneralMade one change in XmlEncryptor Pin
shedao21-Oct-08 10:08
membershedao21-Oct-08 10:08 
NewsTwo other related encryption articles in CodeProject ... Pin
Tony Selke27-Sep-07 6:49
memberTony Selke27-Sep-07 6:49 
GeneralCannot decrypt in VB.Net Pin
stmarcus28-Dec-06 19:24
memberstmarcus28-Dec-06 19:24 
AnswerRe: Cannot decrypt in VB.Net Pin
stmarcus29-Dec-06 8:19
memberstmarcus29-Dec-06 8:19 
QuestionData Type in the Decrypted File Pin
Luis Mora16-Dec-06 14:27
memberLuis Mora16-Dec-06 14:27 
AnswerRe: Data Type in the Decrypted File Pin
Koenraad8-Jan-07 11:38
memberKoenraad8-Jan-07 11:38 
GeneralVB.NET and the null result Pin
Luis Mora16-Dec-06 13:09
memberLuis Mora16-Dec-06 13:09 
GeneralRe: VB.NET and the null result Pin
Koenraad8-Jan-07 11:34
memberKoenraad8-Jan-07 11:34 
Generalbetter ways Pin
ediazc3-Aug-05 8:14
memberediazc3-Aug-05 8:14 
Generalencryption explanation Pin
Ashley van Gerven24-Apr-05 21:28
memberAshley van Gerven24-Apr-05 21:28 
GeneralRe: encryption explanation Pin
Koenraad Blot25-Apr-05 1:02
sussKoenraad Blot25-Apr-05 1:02 
GeneralDataset Encryption Pin
Dale Sides24-Apr-05 14:53
sussDale Sides24-Apr-05 14:53 
GeneralRe: Dataset Encryption Pin
Koenraad25-Apr-05 1:07
memberKoenraad25-Apr-05 1:07 

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