/* *  An implementation of the ARCFOUR algorithm * *  Copyright (C) 2006-2007  Christophe Devine * *  This library is free software; you can redistribute it and/or *  modify it under the terms of the GNU Lesser General Public *  License, version 2.1 as published by the Free Software Foundation. * *  This library 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 *  Lesser General Public License for more details. * *  You should have received a copy of the GNU Lesser General Public *  License along with this library; if not, write to the Free Software *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, *  MA  02110-1301  USA *//* *  The ARCFOUR algorithm was publicly disclosed on 94/09. * *  http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0 */#include "xyssl/config.h"#if defined(XYSSL_ARC4_C)#include "xyssl/arc4.h"/* * ARC4 key schedule */void arc4_setup( arc4_context *ctx, unsigned char *key, int keylen ){    int i, j, k, a;    unsigned char *m;    ctx->x = 0;    ctx->y = 0;    m = ctx->m;    for( i = 0; i < 256; i++ )        m[i] = (unsigned char) i;    j = k = 0;    for( i = 0; i < 256; i++, k++ )    {        if( k >= keylen ) k = 0;        a = m[i];        j = ( j + a + key[k] ) & 0xFF;        m[i] = m[j];        m[j] = (unsigned char) a;    }}/* * ARC4 cipher function */void arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen ){    int i, x, y, a, b;    unsigned char *m;    x = ctx->x;    y = ctx->y;    m = ctx->m;    for( i = 0; i < buflen; i++ )    {        x = ( x + 1 ) & 0xFF; a = m[x];        y = ( y + a ) & 0xFF; b = m[y];        m[x] = (unsigned char) b;        m[y] = (unsigned char) a;        buf[i] = (unsigned char)            ( buf[i] ^ m[(unsigned char)( a + b )] );    }    ctx->x = x;    ctx->y = y;}#if defined(XYSSL_SELF_TEST)#include <string.h>#include <stdio.h>/* * ARC4 tests vectors as posted by Eric Rescorla in sep. 1994: * * http://groups.google.com/group/comp.security.misc/msg/10a300c9d21afca0 */static const unsigned char arc4_test_key[3][8] ={    { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },    { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }};static const unsigned char arc4_test_pt[3][8] ={    { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }};static const unsigned char arc4_test_ct[3][8] ={    { 0x75, 0xB7, 0x87, 0x80, 0x99, 0xE0, 0xC5, 0x96 },    { 0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79 },    { 0xDE, 0x18, 0x89, 0x41, 0xA3, 0x37, 0x5D, 0x3A }};/* * Checkup routine */int arc4_self_test( int verbose ){    int i;    unsigned char buf[8];    arc4_context ctx;    for( i = 0; i < 3; i++ )    {        if( verbose != 0 )            printf( "  ARC4 test #%d: ", i + 1 );        memcpy( buf, arc4_test_pt[i], 8 );        arc4_setup( &ctx, (unsigned char *) arc4_test_key[i], 8 );        arc4_crypt( &ctx, buf, 8 );        if( memcmp( buf, arc4_test_ct[i], 8 ) != 0 )        {            if( verbose != 0 )                printf( "failed\n" );            return( 1 );        }        if( verbose != 0 )            printf( "passed\n" );    }    if( verbose != 0 )        printf( "\n" );    return( 0 );}#endif#endif