[linux.git] / lib / crypto / arc4.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Cryptographic API
 *
 * ARC4 Cipher Algorithm
 *
 * Jon Oberheide <[email protected]>
 */

#include <crypto/arc4.h>
#include <linux/module.h>

int arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len)
{
	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++) {
		u32 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;
}
EXPORT_SYMBOL(arc4_setkey);

void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len)
{
	u32 *const S = ctx->S;
	u32 x, y, a, b;
	u32 ty, ta, tb;

	if (len == 0)
		return;

	x = ctx->x;
	y = ctx->y;

	a = S[x];
	y = (y + a) & 0xff;
	b = S[y];

	do {
		S[y] = a;
		a = (a + b) & 0xff;
		S[x] = b;
		x = (x + 1) & 0xff;
		ta = S[x];
		ty = (y + ta) & 0xff;
		tb = S[ty];
		*out++ = *in++ ^ S[a];
		if (--len == 0)
			break;
		y = ty;
		a = ta;
		b = tb;
	} while (true);

	ctx->x = x;
	ctx->y = y;
}
EXPORT_SYMBOL(arc4_crypt);

MODULE_LICENSE("GPL");
Commit	Line	Data
dc51f257 AB	1	// SPDX-License-Identifier: GPL-2.0-or-later
	2	/*
	3	* Cryptographic API
	4	*
	5	* ARC4 Cipher Algorithm
	6	*
	7	* Jon Oberheide <[email protected]>
	8	*/
	9
	10	#include <crypto/arc4.h>
	11	#include <linux/module.h>
	12
	13	int arc4_setkey(struct arc4_ctx ctx, const u8 in_key, unsigned int key_len)
	14	{
	15	int i, j = 0, k = 0;
	16
	17	ctx->x = 1;
	18	ctx->y = 0;
	19
	20	for (i = 0; i < 256; i++)
	21	ctx->S[i] = i;
	22
	23	for (i = 0; i < 256; i++) {
	24	u32 a = ctx->S[i];
	25
	26	j = (j + in_key[k] + a) & 0xff;
	27	ctx->S[i] = ctx->S[j];
	28	ctx->S[j] = a;
	29	if (++k >= key_len)
	30	k = 0;
	31	}
	32
	33	return 0;
	34	}
	35	EXPORT_SYMBOL(arc4_setkey);
	36
	37	void arc4_crypt(struct arc4_ctx ctx, u8 out, const u8 *in, unsigned int len)
	38	{
	39	u32 *const S = ctx->S;
	40	u32 x, y, a, b;
	41	u32 ty, ta, tb;
	42
	43	if (len == 0)
	44	return;
	45
	46	x = ctx->x;
	47	y = ctx->y;
	48
	49	a = S[x];
	50	y = (y + a) & 0xff;
	51	b = S[y];
	52
	53	do {
	54	S[y] = a;
	55	a = (a + b) & 0xff;
	56	S[x] = b;
	57	x = (x + 1) & 0xff;
	58	ta = S[x];
	59	ty = (y + ta) & 0xff;
	60	tb = S[ty];
	61	out++ = in++ ^ S[a];
	62	if (--len == 0)
	63	break;
	64	y = ty;
65	a = ta;
66	b = tb;
67	} while (true);
68
69	ctx->x = x;
70	ctx->y = y;
71	}
72	EXPORT_SYMBOL(arc4_crypt);
73
74	MODULE_LICENSE("GPL");