; Copyright (c) 2003 Samuel "Wolf on Air" Ljungkvist
;
; Redistribution and use of this software, in source code and binary forms,
; for any legal use, modified or unmodified, is permitted, provided that
; the following conditions are met:
;
; 1: Redistributions of SOURCE CODE must retain the above copyright notice,
;    these conditions, and the following disclaimer.
;
; 2: Redistributions in BINARY FORM must reproduce the above copyright notice,
;    these conditions, and the following disclaimer, in the documentation
;    and/or other materials provided with the distribution.
;
; Disclaimer:
;  This software is provided by the author "as is", and any express or implied
;  warranties, including - but not limited to - the implied warranties of
;  merchantability and fitness for a particular purpose, are DISCLAIMED.
;
;  In no event shall the authors or contributors be liable for any direct,
;  indirect, incidental, special, exemplary, or consequential damages
;  (including, but not limited to, procurement of substitute goods or services;
;  loss of use, data, or profits; or business interruption) however caused,
;  and on any theory of liability, whether in contract, stict liability,
;  or tort (including neglience or otherwise) arising in any way out of
;  the use of this software, even if adviced of the possibility of such damage.


.equ	code,		0x2000
.equ	pm2_phex,	0x0034
.equ	pm2_esc,	0x003E

.org	code

.db	165, 229, 224, 165
.db	 35, 255,   0,   0
.db	  0,   0,   0,   0
.db	  0,   0,   0,   0
.db	  0,   0,   0,   0
.db	  0,   0,   0,   0
.db	  0,   0,   0,   0
.db	255, 255, 255, 255

.db	"ArcFour",0

.org	code+60
ajmp	arcfour_set_key
ajmp	arcfour

;-----

mov	dptr,	#code+0x100

acall	arcfour_set_key

loop:
clr	a
acall	arcfour
lcall	pm2_phex
lcall	pm2_esc
jnc	loop

ret

;-----

arcfour_set_key:
push	acc

mov	dpl,	#0
inc	dph
arcfour_reset_sbox_loop:
mov	a,	dpl
movx	@dptr,	a
inc	dpl
clr	a
cjne	a,	dpl, arcfour_reset_sbox_loop
dec	dph

mov	r6,	#0
arcfour_rand_sbox_loop:
movx	a,	@dptr
add	a,	r6
mov	r6,	a

inc	dph

movx	a,	@dptr
mov	r7,	a
add	a,	r6
mov	r6,	a

push	dpl
mov	dpl,	r6
movx	a,	@dptr
xch	a,	r7
movx	@dptr,	a
pop	dpl

mov	a,	r7
movx	@dptr,	a

dec	dph
inc	dpl

clr	a
cjne	a,	dpl, arcfour_rand_sbox_loop

mov	r6,	#0
mov	r7,	#0

pop	acc
ret

;-----

arcfour:
push	b
push	acc
inc	dph

inc	r6

mov	dpl,	r6
movx	a,	@dptr
mov	b,	a
add	a,	r7
mov	r7,	a

mov	dpl,	r7
movx	a,	@dptr
xch	a,	b
movx	@dptr,	a

mov	dpl,	r6
xch	a,	b
movx	@dptr,	a

add	a,	b
mov	dpl,	a
movx	a,	@dptr

pop	b
xrl	a,	b

dec	dph
pop	b
ret