105 lines
2.7 KiB
C
105 lines
2.7 KiB
C
/* $NetBSD: arc4.c,v 1.5 2003/08/26 20:12:22 thorpej Exp $ */
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/*
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* ARC4 implementation
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* A Stream Cipher Encryption Algorithm "Arcfour"
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* <draft-kaukonen-cipher-arcfour-03.txt>
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*/
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/* This code illustrates a sample implementation
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* of the Arcfour algorithm
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* Copyright (c) April 29, 1997 Kalle Kaukonen.
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* All Rights Reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that this copyright
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* notice and disclaimer are retained.
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*
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* THIS SOFTWARE IS PROVIDED BY KALLE KAUKONEN AND CONTRIBUTORS ``AS
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* IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KALLE
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* KAUKONEN OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: arc4.c,v 1.5 2003/08/26 20:12:22 thorpej Exp $");
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#include <sys/types.h>
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#include <crypto/arc4/arc4.h>
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struct arc4_ctx {
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unsigned int x;
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unsigned int y;
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unsigned int state[256];
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/* was unsigned char, changed to int for performance -- onoe */
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};
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int
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arc4_ctxlen(void)
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{
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return sizeof(struct arc4_ctx);
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}
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void
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arc4_setkey(void *ctxp, const u_char *key, u_int keylen)
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{
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struct arc4_ctx *ctx = ctxp;
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unsigned int i, t, u, ki, si;
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unsigned int *state;
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state = ctx->state;
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ctx->x = 0;
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ctx->y = 0;
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for (i = 0; i < 256; i++)
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state[i] = i;
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ki = si = 0;
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for (i = 0; i < 256; i++) {
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t = state[i];
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si = (si + key[ki] + t) & 0xff;
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u = state[si];
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state[si] = t;
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state[i] = u;
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if (++ki >= keylen)
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ki = 0;
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}
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}
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void
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arc4_encrypt(void *ctxp, u_char *dst, const u_char *src, int len)
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{
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struct arc4_ctx *ctx = ctxp;
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unsigned int x, y, sx, sy;
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unsigned int *state;
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const unsigned char *endsrc;
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state = ctx->state;
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x = ctx->x;
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y = ctx->y;
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for (endsrc = src + len; src != endsrc; src++, dst++) {
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x = (x + 1) & 0xff;
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sx = state[x];
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y = (sx + y) & 0xff;
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state[x] = sy = state[y];
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state[y] = sx;
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*dst = *src ^ state[(sx + sy) & 0xff];
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}
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ctx->x = x;
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ctx->y = y;
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}
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void
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arc4_decrypt(void *ctxp, u_char *dst, const u_char *src, int len)
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{
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arc4_encrypt(ctxp, dst, src, len);
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}
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