[linux-2.6-block.git] / crypto / arc4.c

/*
 * 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>");
Commit	Line	Data
cfa2b54e	1	/*
1da177e4 LT	2	* Cryptographic API
	3	*
	4	* ARC4 Cipher Algorithm
	5	*
	6	* Jon Oberheide <jon@oberheide.org>
	7	*
	8	* This program is free software; you can redistribute it and/or modify
	9	* it under the terms of the GNU General Public License as published by
	10	* the Free Software Foundation; either version 2 of the License, or
	11	* (at your option) any later version.
	12	*
	13	*/
	14	#include <linux/module.h>
	15	#include <linux/init.h>
	16	#include <linux/crypto.h>
	17
	18	#define ARC4_MIN_KEY_SIZE 1
	19	#define ARC4_MAX_KEY_SIZE 256
	20	#define ARC4_BLOCK_SIZE 1
	21
	22	struct arc4_ctx {
	23	u8 S[256];
	24	u8 x, y;
	25	};
	26
6c2bb98b	27	static int arc4_set_key(struct crypto_tfm tfm, const u8 in_key,
560c06ae	28	unsigned int key_len)
1da177e4	29	{
6c2bb98b	30	struct arc4_ctx *ctx = crypto_tfm_ctx(tfm);
1da177e4 LT	31	int i, j = 0, k = 0;
	32
	33	ctx->x = 1;
	34	ctx->y = 0;
	35
cfa2b54e	36	for (i = 0; i < 256; i++)
1da177e4 LT	37	ctx->S[i] = i;
1da177e4 LT	38
cfa2b54e	39	for (i = 0; i < 256; i++) {
1da177e4 LT	40	u8 a = ctx->S[i];
	41	j = (j + in_key[k] + a) & 0xff;
	42	ctx->S[i] = ctx->S[j];
	43	ctx->S[j] = a;
cfa2b54e	44	if (++k >= key_len)
1da177e4 LT	45	k = 0;
	46	}
	47
	48	return 0;
	49	}
	50
6c2bb98b	51	static void arc4_crypt(struct crypto_tfm tfm, u8 out, const u8 *in)
1da177e4	52	{
6c2bb98b	53	struct arc4_ctx *ctx = crypto_tfm_ctx(tfm);
1da177e4 LT	54
	55	u8 *const S = ctx->S;
	56	u8 x = ctx->x;
	57	u8 y = ctx->y;
	58	u8 a, b;
	59
	60	a = S[x];
	61	y = (y + a) & 0xff;
	62	b = S[y];
	63	S[x] = b;
	64	S[y] = a;
	65	x = (x + 1) & 0xff;
	66	out++ = in ^ S[(a + b) & 0xff];
	67
	68	ctx->x = x;
	69	ctx->y = y;
	70	}
	71
	72	static struct crypto_alg arc4_alg = {
	73	.cra_name = "arc4",
	74	.cra_flags = CRYPTO_ALG_TYPE_CIPHER,
	75	.cra_blocksize = ARC4_BLOCK_SIZE,
	76	.cra_ctxsize = sizeof(struct arc4_ctx),
	77	.cra_module = THIS_MODULE,
	78	.cra_list = LIST_HEAD_INIT(arc4_alg.cra_list),
	79	.cra_u = { .cipher = {
	80	.cia_min_keysize = ARC4_MIN_KEY_SIZE,
	81	.cia_max_keysize = ARC4_MAX_KEY_SIZE,
cfa2b54e MV	82	.cia_setkey = arc4_set_key,
	83	.cia_encrypt = arc4_crypt,
	84	.cia_decrypt = arc4_crypt } }
1da177e4 LT	85	};
	86
	87	static int __init arc4_init(void)
	88	{
	89	return crypto_register_alg(&arc4_alg);
	90	}
	91
	92
	93	static void __exit arc4_exit(void)
	94	{
	95	crypto_unregister_alg(&arc4_alg);
	96	}
	97
	98	module_init(arc4_init);
	99	module_exit(arc4_exit);
	100
	101	MODULE_LICENSE("GPL");
	102	MODULE_DESCRIPTION("ARC4 Cipher Algorithm");
	103	MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>");