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#IF 0
Code appears below for the following three files:
RC4OBJ.INC Class implementation of the RC4 encryption algorithm
RC4OBJ.BAS Test bed program illustrating use of RC4OBJ.INC
RC4UTIL.BAS Utility macros and functions
[b]Note: See the test bed code (RC4OBJ.BAS) for examples illustrating use
of the code in RC4OBJ.INC.[/b]
Although the stream cipher RC4 is today often treated as obsolete for
long-term, high security purposes, it still remains extremely useful,
especially for short-term encryption of strings whose length is varied
or unpredictable.
This PB implementation of RC4 is hereby placed in the public domain.
Use it as you wish.
Greg Turgeon
8/2008
#ENDIF
'=====================================================================
'-- RC4OBJ.INC
'-- WIN32 API not required
'-- Uses no global data
'-- Compiles with either PBWIN 9.0 or PBCC 5.0
'=====================================================================
%SUBKEY_SIZE = 256
TYPE ENCRYPTION_CONTEXT
UserKeyLength AS LONG
UserKey AS BYTE PTR
InBlock AS BYTE PTR
OutBlock AS BYTE PTR
BlockLength AS LONG
END TYPE
'===========================================================
CLASS RC4Class
'===========================================================
INSTANCE UserKeyLength, BlockLength, RC4X, RC4Y AS LONG
INSTANCE UserKey, InBlock, OutBlock, RC4State AS BYTE PTR
INSTANCE State_Buffer AS STRING * %SUBKEY_SIZE '<-- encryption subkey buffer
'====================
CLASS METHOD CREATE
State_Buffer = nul$(%SUBKEY_SIZE)
RC4State = varptr(State_Buffer)
RC4X = 0 : RC4Y = 0
END METHOD
'====================
CLASS METHOD Init(Ctx AS ENCRYPTION_CONTEXT) AS LONG
LOCAL keydata$, pkeydata, tmp AS BYTE PTR
LOCAL i, index1, index2, passlen AS LONG
passlen = Ctx.UserKeyLength
keydata = nul$(passlen)
pkeydata = strptr(keydata)
poke$ pkeydata, peek$(Ctx.UserKey, passlen)
InBlock = Ctx.InBlock
OutBlock = Ctx.OutBlock
BlockLength = Ctx.BlockLength
tmp = (RC4State+%SUBKEY_SIZE)-1
! push esi
! mov esi, tmp
! mov ecx, %SUBKEY_SIZE-1
LoopTop:
! mov [esi], cl
! dec ecx
! js LoopDone
! dec esi
! jmp LoopTop
LoopDone:
! pop esi
tmp = RC4State
for i = 0 to %SUBKEY_SIZE-1
index2 = (@pkeydata[index1] + @tmp[i] + index2) AND 255
swap @tmp[i], @tmp[index2]
index1 = (index1 + 1) mod passlen
next i
END METHOD
'====================
CLASS METHOD DESTROY
poke$ RC4State, nul$(%SUBKEY_SIZE)
RC4X = 0 : RC4Y = 0
END METHOD
'=======================================
INTERFACE RC4Interface
'=======================================
INHERIT iUnknown
'====================
METHOD Process(Ctx AS ENCRYPTION_CONTEXT) AS LONG
REGISTER i AS LONG, xorindex AS LONG
LOCAL pin, pout AS BYTE PTR
Me.Init(Ctx)
pin = InBlock
pout = OutBlock
for i = 1 to BlockLength
RC4X = (RC4X + 1) AND 255
RC4Y = (@RC4State[RC4X] + RC4Y) AND 255
swap @RC4State[RC4X], @RC4State[RC4Y]
xorindex = (@RC4State[RC4X] + @RC4State[RC4Y]) AND 255
@pout = @pin XOR @RC4State[xorindex]
incr pin : incr pout
next i
END METHOD
END INTERFACE
END CLASS
'-- end RC4OBJ.INC
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