by Glenn Larsson (5 Submissions)
Category: String Manipulation
Compatability: Visual Basic 3.0
Difficulty: Unknown Difficulty
Originally Published: Mon 15th November 1999
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
A simple Substitution function. Works on HEX data. (This generates the SBox)
VBcoders
' A key dependent SBox, feed a key dependent value (You figure it out; dead easy) info
' this function and voila..
'
' Disclaimer: This is not supposed to be used for any other purpose than to learn what an SBox is.
' This is not an encryption system but a part of one, if you use it AS one = Good luck!
'
' ABSOLUTELY NO SUPPORT will be provided via Email!
' Free for educational use (C) 1999 Glenn Larsson ([email protected])
'
Dim A(256) As Integer
' MOD 256 it to 0>=n<=255
SBoxSeed = SBoxSeed Mod 256
' Fill the array with stuff
' -------------------------
For Z = 0 To 255
A(Z) = (154 + Z) Mod 256
Next Z
' Generate the Substitution Box using the "Stuff" in the array
' ------------------------------------------------------------
For P = 0 To SBoxSeed
For x = (67 + P) To 3 Step -1
For Z = 0 To 255 Step (4 + x)
s = Z + x
If s > 255 Then s = s Mod 256
C = A(s)
B = A(Z)
A(s) = B
A(Z) = C
Next Z
Next x
Next P
' Convert the Array to a Hex string (Duuh?)
' -----------------------------------------
H:
For Z = 0 To 255
L = ""
If Len(Trim(Hex(A(Z)))) < 2 Then L = "0"
TOT = TOT & L & Hex(A(Z))
Next Z
GenerateSBox = TOT
End Function
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