X-Git-Url: https://git.cryptolib.org/?a=blobdiff_plain;f=arcfour-asm.S;h=6c8c351f677f6b68e218fd2857a3a2cee587ff53;hb=17332291e15183d71d88ed868275e3cb53917180;hp=78d0491ed0c78b3001d3b5ea28fe3a4cb66e4aae;hpb=3c995d0a8faeb9d37927d48e20fc45d839e066ea;p=avr-crypto-lib.git

diff --git a/arcfour-asm.S b/arcfour-asm.S
index 78d0491..6c8c351 100644
--- a/arcfour-asm.S
+++ b/arcfour-asm.S
@@ -1,74 +1,85 @@
+/* arcfour-asm.S */
+/*
+    This file is part of the This file is part of the AVR-Crypto-Lib.
+    Copyright (C) 2008  Daniel Otte (daniel.otte@rub.de)
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
 /* 
- * File:		arcfour-asm.S
- * Author:	Daniel Otte
- * Date: 	07.06.2006
- * License: GPL
+ * File:        arcfour-asm.S
+ * Author:      Daniel Otte
+ * Date:        2006-07-06
+ * License:     GPLv3 or later
  * Description: Implementation of the ARCFOUR (RC4 compatible) stream cipher algorithm.
  * 
  */
  
+#include <avr/io.h>
+#include "avr-asm-macros.S"
+ 
  /* +---+---+---------------------+
  *  | i | j | ......<256>........ |
  *  +---+---+---------------------+
  */
  
 .global arcfour_init
-
-;== arcfour_init ==
-;  this function initialises the context
-; param1: 16-bit pointer to a ctx struct
-;	given in r25,r24
-; param2: 16-bit pointer to a key
-;	given in r23,r22
-; param1: 8-bit integer indicating keylength in byte
-;	given in 	r20
-
+/*
+ *== arcfour_init ==
+ *  this function initialises the context
+ * param1: 16-bit pointer to the key
+ *	given in r24:r25
+ * param2: 8-bit integer indicating keylength in byte
+ *	given in r22
+ * param3: 16-bit pointer to a ctx struct
+ *	given in r20:r21
+ */
 arcfour_init:
-	push r29
-	push r28
-	push r2
-	
-	movw r26, r24	/* X points to ctx */
-	movw r30, r22	/* Z points to key */
+	push_ r28, r29
+	movw r26, r20   /* X points to ctx */
+	movw r30, r24   /* Z points to key */
 	st X+, r1
-	st X+, r1		/* X points to S */
+	st X+, r1       /* X points to S */
+	movw r20, r26   /* store pointer to S in r21:r20 */
 	
 1:		
 	st X+, r1 
 	inc r1
 	brne 1b
 	
-	adiw r24, 2		/* r24:r25 points to S */
-	clr r21			/* r21 is j */
-	mov r18, r20		/* r18 is keyindex counter */
+	movw r26, r20
+	add r22, r30         /* r18 is keyindex counter */
 	clr r0
+	clr r19
 2:
-	movw r26, r24
-	ld r19, Z+
-	add r21, r19		/* j+= key[i%length] */
-	
-	add r26, r1
-	adc r27, r0
-	ld r19, X
-	add r21, r19		/* j += S[i] */
-	
-	dec r18		/* check the key-index counter */
+	ld r23, X
+	ld r18, Z+
+	add r19, r18
+	add r19, r23
+	movw r28, r20   /* load pointer to S in Y */
+	add r28, r19
+	adc r29, r1
+	ld r18, Y
+	st Y,  r23
+	st X+, r18
+	cp r30, r22
 	brne 3f
-	movw r30, r22
-	mov r18, r20
-3:	/* now swap(S[i], S[j]) */ /* r19 is still S[i] */
-	movw r28, r24 
-	add r28, r21
-	adc r29, r0		/* Y points to S[j]*/
-	ld r2, Y
-	st Y, r19
-	st X, r2	
-	inc r1
+	movw r30, r24
+3:		
+	inc r0
 	brne 2b	
-	
-	pop r2
-	pop r28
-	pop r29
+	pop_ r29, r28
 	ret
 
 /*