Question

For Extra Security, i would like to Encrypt/Decrypt a MS Access 2000 (*.mdb) Database File.

I am using Delphi 7 and I am looking for a free or opensource solution (possible just two functions that allow you to pass a file name and a key).

I would like to perform the decrypt before my app starts, and the encrypt when the app shuts down. Where are the best places to do this. OnCreate, OnDestroy events?

I assume i would first have to create a small utility which uses the encrypt portion of the solution to encrypt the database file first?

thanks

Answer 1

I understand the reasons which you have to encrypt your old access database , because the security of access 2000 and 2003 is very weak. but my primary recommendation is which try to upgrade to Access 2007 or higher which uses the Microsoft Cryptographic API, and incorporates significant improvements in security.

If you can’t upgrade, here i leave an option to encrypt your mdb file.

1) to encrypt you data you can use the JwaWinCrypt unit which is part of the Jedi JWSCL library, you can download this library from here.

check this sample function which uses 3DES algorithm to encrypt a file.

uses
  Classes,
  JwaWinType,
  JwaWinCrypt,
  SysUtils;


procedure CryptFile(Const InFileName, OutFileName, Password: AnsiString; Encrypt: Boolean);
const
  BufferSize=1024*64;
var
  StreamSource  : TFileStream;
  StreamDest    : TFileStream;
  CRYPTPROV     : HCRYPTPROV;
  CRYPTHASH     : HCRYPTHASH;
  CRYPTKEY      : HCRYPTKEY;
  Buffer        : LPBYTE;
  BytesIn       : DWORD;
  Final         : Boolean;
begin
  CryptAcquireContext(CRYPTPROV, nil, nil, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
  try
      CryptCreateHash(CRYPTPROV, CALG_3DES_112, 0, 0, CRYPTHASH);
      try
        CryptHashData(CRYPTHASH, @Password[1], Length(Password), 0);
        CryptDeriveKey(CRYPTPROV, CALG_3DES, CRYPTHASH, 0, CRYPTKEY);
      finally
        CryptDestroyHash(CRYPTHASH);
      end;

      StreamSource := TFileStream.Create(InFileName, fmOpenRead or fmShareDenyWrite);
      StreamDest   := TFileStream.Create(OutFileName, fmCreate);
      try
        GetMem(Buffer, BufferSize);
        try
            repeat
              BytesIn   := StreamSource.Read(Buffer^, BufferSize);
              Final     := (StreamSource.Position >= StreamSource.Size);
              if Encrypt then
                CryptEncrypt(CRYPTKEY, 0, Final, 0, Buffer, BytesIn, BytesIn)
              else
              CryptDecrypt(CRYPTKEY, 0, Final, 0, Buffer, BytesIn);
              StreamDest.Write(Buffer^, BytesIn);
            until Final;
        finally
         FreeMem(Buffer, BufferSize);
        end;

      finally
        StreamSource.Free;
        StreamDest.Free;
      end;
  finally
    CryptReleaseContext(CRYPTPROV, 0);
  end;
end;

and use in this way

to encrypt a file

 CryptFile('C:\temp\in.zip', 'C:\temp\out.zip','fdkjldf3832kka83' ,True);

to decrypt a file

 CryptFile('C:\temp\out.zip', 'C:\temp\in.zip','fdkjldf3832kka83' ,True);

2) about the location of the code to encryot and decrypt the data, will depends of the design of you application.

3) keep in mind that if your application crashes your data will be unprotected.

4) maybe the best option is build a small application which decrypt your data and launch your main application and stay monitoring the status until the main application ends. and then encypt your data again.