/*  * Cryptographic API * * ARC4 Cipher Algorithm * * Jon Oberheide <jon@oberheide.org> * * 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 2 of the License, or * (at your option) any later version. * */#include <linux/module.h>#include <linux/init.h>#include <linux/crypto.h> #define ARC4_MIN_KEY_SIZE	1#define ARC4_MAX_KEY_SIZE	256#define ARC4_BLOCK_SIZE		1 struct arc4_ctx {	u8 S[256];	u8 x, y;}; static int arc4_set_key(struct crypto_tfm *tfm, const u8 *in_key,			unsigned int key_len){	struct arc4_ctx *ctx = crypto_tfm_ctx(tfm);	int i, j = 0, k = 0; 	ctx->x = 1;	ctx->y = 0; 	for(i = 0; i < 256; i++)		ctx->S[i] = i; 	for(i = 0; i < 256; i++)	{		u8 a = ctx->S[i];		j = (j + in_key[k] + a) & 0xff;		ctx->S[i] = ctx->S[j];		ctx->S[j] = a;		if(++k >= key_len)			k = 0;	} 	return 0;} static void arc4_crypt(struct crypto_tfm *tfm, u8 *out, const u8 *in){	struct arc4_ctx *ctx = crypto_tfm_ctx(tfm); 	u8 *const S = ctx->S;	u8 x = ctx->x;	u8 y = ctx->y;	u8 a, b; 	a = S[x];	y = (y + a) & 0xff;	b = S[y];	S[x] = b;	S[y] = a;	x = (x + 1) & 0xff;	*out++ = *in ^ S[(a + b) & 0xff]; 	ctx->x = x;	ctx->y = y;} static struct crypto_alg arc4_alg = {	.cra_name		=	"arc4",	.cra_flags		=	CRYPTO_ALG_TYPE_CIPHER,	.cra_blocksize		=	ARC4_BLOCK_SIZE,	.cra_ctxsize		=	sizeof(struct arc4_ctx),	.cra_module		=	THIS_MODULE,	.cra_list		=	LIST_HEAD_INIT(arc4_alg.cra_list),	.cra_u			=	{ .cipher = {	.cia_min_keysize	=	ARC4_MIN_KEY_SIZE,	.cia_max_keysize	=	ARC4_MAX_KEY_SIZE,	.cia_setkey	   	= 	arc4_set_key,	.cia_encrypt	 	=	arc4_crypt,	.cia_decrypt	  	=	arc4_crypt } }}; static int __init arc4_init(void){	return crypto_register_alg(&arc4_alg);}  static void __exit arc4_exit(void){	crypto_unregister_alg(&arc4_alg);} module_init(arc4_init);module_exit(arc4_exit); MODULE_LICENSE("GPL");MODULE_DESCRIPTION("ARC4 Cipher Algorithm");MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>");