Tim

I'm going to want encrypt a small file or two as part of an app. Is there a way of accessing the encryption you've built into ElevateDB?


Roy Lambert

Roy,

<< I'm going to want encrypt a small file or two as part of an app. Is there
a way of accessing the encryption you've built into ElevateDB? >>

Sure.  You can use it via the edbcommon unit and the TEDBBlowfish object.
Although, the easiest way might be to simply use the TEDBMemoryStream in the
the edbcommon.pas unit, which has these methods:

        procedure InitEncryption(PasswordDigest: TEDBDigest);
        procedure Encrypt(Count: Integer=0);
        procedure Decrypt(Count: Integer=0);

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim

Brill - thanks.

Roy Lambert

Tim

I've reached a point where I want to test things out. I've tried:



procedure TForm1.AdvGlowButton1Click(Sender: TObject);
var
interim: string;
ts: TEDBMemoryStream;
bf: TEDBDigest;
begin
if Saver.Execute then begin
 interim := Trim(Licencee.Text) + '¬' + MaxUsers.Text + '¬' + LicenceCode.Text;
 ts := TEDBMemoryStream.Create;
 bf := TEDBDigest.Create;
 bf.AsString := 'roylambert';
 ts.InitEncryption(bf);
 ts.WriteString(interim, Length(interim));
 ts.Encrypt(Length(interim));
 TMemoryStream(ts).SaveToFile(Saver.FileName);
end;
end;

This works until I include ts.Encrypt(Length(interim)); then I get strange results

---------------------------
Lm
---------------------------
Cannot create file "”:\Users\Roy Lambert\Documents\xxx.tfr". The system cannot find the path specified.
---------------------------
OK  
---------------------------

I'm obviously doing something wrong, but I have no idea what.

Roy Lambert

Roy,

<< This works until I include ts.Encrypt(Length(interim)); then I get
strange results >>

What the heck is this:

TMemoryStream(ts).SaveToFile(Saver.FileName);

TEDBMemoryStream is *not* a descendant of TMemoryStream or TStream.

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim


1. The rest is alright though?
2. Consider me an innocent victim of your naming scheme

Roy Lambert

Roy,

<< 1. The rest is alright though? >>

Yes.

<< 2. Consider me an innocent victim of your naming scheme >>

Well, originally it was a descendant of TStream, but I had to change that
all around due to .NET and various issues with trying to override all of the
variations the TStream methods have taken over the years since D5.

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim


Once I've got it in there how do I get at the encrypted version to save it? I've been trying various things but nothing works so far.

Roy Lambert

Roy,

<< Once I've got it in there how do I get at the encrypted version to save
it? I've been trying various things but nothing works so far. >>

You can access the memory buffer directly using the Memory property.
However, I forgot that there's a TEDBStreamWrapper class defined in
edbcomps.pas.  You create it like this:

constructor TEDBStreamWrapper.Create(SourceStream: TStream);

which means that you can use it to interface between a normal TStream and a
TEDBStream (or descendant like TEDBMemoryStream).

You would use it like this:

var
   MyFileStream: TFileStream;
   MyStreamWrapper: TEDBStreamWrapper;
   MyMemoryStream: TEDBMemoryStream;
begin
   MyFileStream:=.....
   MyStreamWrapper:=TEDBStreamWrapper.Create(MyFileStream);
   MyMemoryStream:=....
   // Work with the memory stream, encrypt it, etc.
   MyMemoryStream.SaveToStream(MyStreamWrapper);
   // Free everything up here, etc.
end;

And that should do the trick.

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim

>However, I forgot that there's a TEDBStreamWrapper class defined in
>edbcomps.pas.

Glad I'm not the only one that does that Unfortunately its not exposed, but I'm happy to work with the Memory property. One (hopefully) final question: How do I decrypt it?

I can stuff my data in and encrypt it and using

for cntr := 1 to Length(ts.Memory) do xyz:=xyz+char(ts.memory[cntr]);

get it out to have a look at (strangely with my data the last few characters are always in the clear).

What I'm doing now as a test is

interim := Trim(Licencee.Text) + '¬' + MaxUsers.Text + '¬' + LicenceCode.Text;
ts := TEDBMemoryStream.Create;
bf := TEDBDigest.Create;
bf.AsString := '1qw'+#8+#160+'roylambertqw42ecccrtyuiopasdfghjkl';
ts.InitEncryption(bf);
ts.WriteString(interim, Length(interim));
ts.Position := 0;
ts.Encrypt(Length(interim));
ts.Position := 0;
ts.Decrypt(length(ts.Memory));
ts.Position := 0;
for cntr := 1 to Length(ts.Memory) do xyz:=xyz+char(ts.memory[cntr]);
showmessage(inttostr(length(xyz))+'   '+xyz);
bf.Free;
ts.Free;

Roy Lambert