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Posted 31 Oct 2001


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Serializing encrypted data

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31 Oct 20011 min read
How to serialize encrypted data using CArchive


I've recently discovered the CArchive class. I've never used it before. I had to save my application's preferences and I thought I would try to serialize it to a file using the CArchive class. Then only problem is that I need to encrypt the data.

So I sat down and wrote a CFile derived class to encrypt data while saving it.

In the demo project I've used the Rijndael algorithm. The implementation was written by Szymon Stefanek.


The most important functions of the CFile class are Read and Write. Since these are virtual functions, you can override them with your own functions.

In the class, there are 2 callback functions. The class uses both to encrypt and to decrypt the data.

typedef UINT (FileEncryptProc)(const BYTE *pBuffer,UINT dwSize,BYTE *pDestination,DWORD


  • pBuffer - Pointer to the data
  • dwSize - Data length in bytes
  • pDestination - Pointer to a destination buffer
  • dwParam - User defined parameter

Return value:

New data length.


You set the callbacks using the SetEncryption function

//  These are the encryption and decryption functions

UINT Encrypt(const BYTE *pBufIn, UINT nSize, BYTE *pBufOut, 
             DWORD dwParam)
    return ((Rijndael*)dwParam)->padEncrypt(pBufIn, 
        nSize, pBufOut);

UINT Decrypt(const BYTE *pBufIn, UINT nSize, BYTE *pBufOut, 
             DWORD dwParam)
    return ((Rijndael*)dwParam)->padDecrypt(pBufIn, 
        nSize, pBufOut);

f.SetEncryption(&Encrypt, (DWORD)&rijEncrypt, &Decrypt, 
                (DWORD)&rijDecrypt); // Set the encryption callbacks


In the demo project, I've created two Rijndael objects. One for encryption and one for decryption. Both objects were initialized using the same key. I've also created a CFileEx object and set it's callbacks to my defined functions.

From that point, I can create a CArchive object and use it as normal with my file. As you can see in the demo, I am writing and reading various data types to and from the archive.


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About the Author

Gilad Novik
Web Developer
Israel Israel
Gilad was born accidently to a pair of old lesbians. His childhood was full of vibrators and drugs. Married without kids. Has 14 grandsons around the world, 4 crocodiles, 2 mushrooms and a green alien living behind the refrigerator.

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Comments and Discussions

Generalin out parameters Pin
selami17-Nov-03 0:08
Memberselami17-Nov-03 0:08 
GeneralPlease explain with more details Pin
Gilad Novik17-Nov-03 0:20
MemberGilad Novik17-Nov-03 0:20 
GeneralRe: Please explain with more details Pin
p_hose17-Nov-03 2:01
Memberp_hose17-Nov-03 2:01 
GeneralRe: Please explain with more details Pin
Gilad Novik17-Nov-03 2:43
MemberGilad Novik17-Nov-03 2:43 
Generalin out parameters Pin
Anonymous17-Nov-03 0:07
MemberAnonymous17-Nov-03 0:07 
QuestionHelp Please?? Pin
xxhimanshu30-Oct-03 20:34
Memberxxhimanshu30-Oct-03 20:34 
AnswerRe: Help Please?? Pin
Gilad Novik1-Nov-03 21:56
MemberGilad Novik1-Nov-03 21:56 
Generalproblem with bigger objects Pin
eXplodus19-May-03 5:57
MembereXplodus19-May-03 5:57 
hi there ...

i try your class ... and it works fine. if i serialize little objects below 10k in the file size.
but if i try to use it with a big and deep and complex serialization then i got problems with your
implementation. i really try to figure out from where the problem occours but i dont find anything.

if i use a normal CFile all works really fine. But with your CFileEx i can not decrypt after a come above 10k.

did you get this problem also?
or did you have any idea's where the problem occours?

thx anyway
GeneralRe: problem with bigger objects Pin
kinmenhans11-Apr-13 0:22
Memberkinmenhans11-Apr-13 0:22 

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