[d7dadcb4] | 1 | /*
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| 2 | * Copyright (c) 2015 Jan Kolarik
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| 3 | * All rights reserved.
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| 4 | *
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| 5 | * Redistribution and use in source and binary forms, with or without
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| 6 | * modification, are permitted provided that the following conditions
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| 7 | * are met:
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| 8 | *
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| 9 | * - Redistributions of source code must retain the above copyright
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| 10 | * notice, this list of conditions and the following disclaimer.
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| 11 | * - Redistributions in binary form must reproduce the above copyright
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| 12 | * notice, this list of conditions and the following disclaimer in the
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| 13 | * documentation and/or other materials provided with the distribution.
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| 14 | * - The name of the author may not be used to endorse or promote products
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| 15 | * derived from this software without specific prior written permission.
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| 16 | *
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 27 | */
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| 28 |
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| 29 | /** @file rc4.c
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| 30 | *
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| 31 | * Implementation of ARC4 symmetric cipher cryptographic algorithm.
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| 32 | *
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| 33 | */
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| 34 |
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| 35 | #include <errno.h>
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| 36 | #include <mem.h>
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| 37 |
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| 38 | #include "crypto.h"
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| 39 |
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| 40 | /* Sbox table size. */
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| 41 | #define SBOX_SIZE 256
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| 42 |
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| 43 | /**
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| 44 | * Swap two values in sbox.
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| 45 | *
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| 46 | * @param i First index of value in sbox to be swapped.
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| 47 | * @param j Second index of value in sbox to be swapped.
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| 48 | * @param sbox Sbox to be modified.
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| 49 | */
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| 50 | static void swap(size_t i, size_t j, uint8_t *sbox)
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| 51 | {
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| 52 | uint8_t temp = sbox[i];
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| 53 | sbox[i] = sbox[j];
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| 54 | sbox[j] = temp;
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| 55 | }
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| 56 |
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| 57 | /**
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| 58 | * Sbox initialization procedure.
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| 59 | *
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| 60 | * @param key Input key.
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| 61 | * @param key_size Size of key sequence.
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| 62 | * @param sbox Place for result sbox.
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| 63 | */
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| 64 | static void create_sbox(uint8_t *key, size_t key_size, uint8_t *sbox)
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| 65 | {
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| 66 | for(size_t i = 0; i < SBOX_SIZE; i++) {
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| 67 | sbox[i] = i;
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| 68 | }
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| 69 |
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| 70 | uint8_t j = 0;
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| 71 | for(size_t i = 0; i < SBOX_SIZE; i++) {
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| 72 | j = j + sbox[i] + key[i % key_size];
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| 73 | swap(i, j, sbox);
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| 74 | }
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| 75 | }
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| 76 |
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| 77 | /**
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| 78 | * ARC4 encryption/decryption algorithm.
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| 79 | *
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| 80 | * @param key Input key.
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| 81 | * @param key_size Size of key sequence.
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| 82 | * @param input Input data sequence to be processed.
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| 83 | * @param input_size Size of input data sequence.
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[a931b7b] | 84 | * @param skip Number of bytes to be skipped from the beginning of key stream.
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[d7dadcb4] | 85 | * @param output Result data sequence.
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| 86 | *
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| 87 | * @return EINVAL when input or key not specified, ENOMEM when pointer for
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| 88 | * output is not allocated, otherwise EOK.
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| 89 | */
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| 90 | int rc4(uint8_t *key, size_t key_size, uint8_t *input, size_t input_size,
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[a931b7b] | 91 | size_t skip, uint8_t *output)
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[d7dadcb4] | 92 | {
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| 93 | if(!key || !input)
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| 94 | return EINVAL;
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| 95 |
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| 96 | if(!output)
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| 97 | return ENOMEM;
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| 98 |
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| 99 | /* Initialize sbox. */
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| 100 | uint8_t sbox[SBOX_SIZE];
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| 101 | create_sbox(key, key_size, sbox);
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| 102 |
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[a931b7b] | 103 | /* Skip first x bytes. */
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| 104 | uint8_t i = 0, j = 0;
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| 105 | for(size_t k = 0; k < skip; k++) {
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[cc575ef9] | 106 | i = i + 1;
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[a931b7b] | 107 | j = j + sbox[i];
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| 108 | swap(i, j, sbox);
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| 109 | }
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| 110 |
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[d7dadcb4] | 111 | /* Processing loop. */
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[a931b7b] | 112 | uint8_t val;
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[d7dadcb4] | 113 | for(size_t k = 0; k < input_size; k++) {
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[cc575ef9] | 114 | i = i + 1;
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[d7dadcb4] | 115 | j = j + sbox[i];
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| 116 | swap(i, j, sbox);
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| 117 | val = sbox[sbox[i] + sbox[j]];
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| 118 | output[k] = val ^ input[k];
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| 119 | }
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| 120 |
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| 121 | return EOK;
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| 122 | } |
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