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#1
KimChi

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This tutorial was made by Sora. If you are going
to spread this tutorial on other forums, give credit.


What you will need:
Visual Basic 6 or Visual Basic 6 Portable
A RC4 module
A brain


The RC4 module and Visual Basic 6 Portable will have the download links
at the end of this tutorial.

TABLE OF CONTENTS:
1. Introduction
2. Building your crypter
3. Conclusion

1. Introduction

RC4:
In cryptography, RC4 (also known as ARCFOUR or ARC4 meaning
Alleged RC4, see below) is the most widely used stream cipher and is
used in protocols such as Secure Sockets Layer (SSL) (to protect
Internet traffic) and WEP (to secure wireless networks).

Stub:
A method stub or simply stub in software development is a piece of code
used to stand in for some other programming functionality. A stub may
simulate the behavior of existing code (such as a procedure on a remote
machine) or be a temporary substitute for yet-to-be-developed code.
Stubs are therefore most useful in porting, distributed computing as
well as general software development and testing.

Builder:
A builder is usually the client to make/do something to a file, and it
is supposed to go with a stub. The builder usually allows the stub to
simulate the behaivor of existing code, and than it makes the file/does
something to a file.

2. Building your crypter.

Now, open up Visual Basic 6 or Visual Basic Portable. To
make the task easier, open two Visual Basic 6 programs. One is
going to be the builder, and one is going to be the stub.

Now, lets start on the builder. Add a RC4 module, and lets go on. First
of all, add one label that says "File Path:", a text box right beside
"File Path:", a button that says "Browse" or "...", and another button
that says "Crypt" or "Build". Now, lets add the CommonDialog
control. Add a CommonDialog and name it commondlg. Now, lets
double click the button that says "Browse" or "...". Add this code, and
I'll explain it.

Code:
With commondlg 'CommonDialog1.
.Filter = "Executable files | *.exe" 'The file used for crypting. (*.exe)
.DialogTitle = "Please select a executable file..." 'The title of the dialog.
.ShowOpen 'Show the dialog.
End With
TextBox1.Text = commondlg.FileName 'Make TextBox1.Text as the selected filename.

The With commondlg command calls CommonDialog1.
The .Filter part allows you to choose what files you only want to
be selected.
The .DialogTitle command is the title of the dialog (the prompt
that tells you which file you want to select for crypting).
The .ShowOpen command shows the dialog.
End With will
end CommonDialog1.
And finally, the TextBox1.Text = commondlg.FileName command makes
TextBox1.text show the selected filename.

Now, click the button that says "Build" or "Crypt". Add this code. It
explains it, so please take time to read what it says.
Code:
Dim sStub As String, sFile As String 'This command will declare the two strings.
Open App.Path & "\stub.exe" For Binary As #1 'Opens up the stub.
sStub = Space(LOF(1)) 'This declares the space.
Get #1, , sStub 'This puts in a space in the file.
Close #1 'This closes the file.

Open TextBox1.Text For Binary As #1 'Opens up the stub.
sFile = Space(LOF(1)) 'This declares the space.
Get #1, , sFile 'This puts a space in the file.
Close #1 'This closes the file.

Open App.Path & "\output.exe" For Binary As #1 'This creates the crypted file as "output.exe".
Put #1, , sStub & FileSplit & RC4(sFile, Pass) 'This adds the option FileSplit and the RC4 option.
Close #1 'This closes the file.

MsgBox ("File crypted successfully!") 'This is the prompt to show the message that the program successfully crypted the file.

Now, you might have an error that will show you that
FileSplit and Pass is not declared. To do so, we will add the
declarations on the top of the coding.

Code:

Const FileSplit = "<@#@>" 'The file split.
Const Pass = "s0rasRC4Tutorial" 'The RC4 password.

For this tutorial, we will be using "s0rasRC4Tutorial" as
the RC4 password.

Now, lets start on the stub. Add the RC4 module, and make a new module
called modMain. Add this code in modMain:
Code:
Const FileSplit = "<@#@>" 'The file split.
Const Pass = "s0rasRC4Tutorial" 'The RC4 password; It must be the same as the one on the builder!

Public Declare Function ShellExecute Lib "Shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, ByVal lpszOp As String, ByVal lpszFile As String, ByVal lpszParams As String, ByVal LpszDir As String, ByVal FsShowCmd As Long) As Long 'Calls the ShellExecute command.

Public Sub Main() 'The main part of the stub.
Dim sStub As String, sFile As String 'This will declare the strings again, just like we did on the builder.
Open App.Path & "\" & App.EXEName & ".exe" For Binary As #1 'Opens up the selected .exe file.
sStub = Space(LOF(1)) 'This will declare the space.
Get #1, , sStub 'This puts a space in the file.
Close #1 'This closes the file.

sFile = Split(sStub, FileSplit)(1) 'This will split the file and the stub.
Open Environ("tmp") & "\decrypted.exe" For Binary As #1 'This will make a decrypted file in the RC4 folder.
Put #1, , RC4(sFile, Pass) 'This will add the RC4 password to the file with the selected RC4 password.

Call ShellExecute(0, vbNullString, Environ("tmp") & "\decrypted.exe", vbNullString, vbNullString, 1) 'Calls the ShellExecute command and drops the decrypted file in the temporary files folder.

End Sub 'This ends "Public Sub Main()".

The code will be teaching you. Once you're done, remove the
Form1.

3. Conclusion
I hope you liked this tutorial, and I hope you learned a lot about
crypting with RC4!
RC4 module: RC4 Encryption in VB

I am Sora from HF. :great:

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#2
lonestar

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Level 0
Level 0
thanks for this!

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