| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: xtea.c,v 1.3 2004/04/08 01:36:15 mdw Exp $ |
| 4 | * |
| 5 | * The Extended Tiny Encryption Algorithm |
| 6 | * |
| 7 | * (c) 2000 Straylight/Edgeware |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of Catacomb. |
| 13 | * |
| 14 | * Catacomb is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU Library General Public License as |
| 16 | * published by the Free Software Foundation; either version 2 of the |
| 17 | * License, or (at your option) any later version. |
| 18 | * |
| 19 | * Catacomb is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU Library General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU Library General Public |
| 25 | * License along with Catacomb; if not, write to the Free |
| 26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 27 | * MA 02111-1307, USA. |
| 28 | */ |
| 29 | |
| 30 | /*----- Header files ------------------------------------------------------*/ |
| 31 | |
| 32 | #include <mLib/bits.h> |
| 33 | |
| 34 | #include "blkc.h" |
| 35 | #include "gcipher.h" |
| 36 | #include "paranoia.h" |
| 37 | #include "xtea.h" |
| 38 | |
| 39 | /*----- Global variables --------------------------------------------------*/ |
| 40 | |
| 41 | const octet xtea_keysz[] = { KSZ_RANGE, XTEA_KEYSZ, 0, 16, 1 }; |
| 42 | |
| 43 | /*----- Main code ---------------------------------------------------------*/ |
| 44 | |
| 45 | /* --- @xtea_init@ --- * |
| 46 | * |
| 47 | * Arguments: @xtea_ctx *k@ = pointer to key block |
| 48 | * @const void *buf@ = pointer to key buffer |
| 49 | * @size_t sz@ = size of key material |
| 50 | * |
| 51 | * Returns: --- |
| 52 | * |
| 53 | * Use: Initializes an XTEA key buffer. The key buffer must be 16 |
| 54 | * bytes long. |
| 55 | */ |
| 56 | |
| 57 | void xtea_init(xtea_ctx *k, const void *buf, size_t sz) |
| 58 | { |
| 59 | octet kb[16]; |
| 60 | const octet *p; |
| 61 | |
| 62 | KSZ_ASSERT(xtea, sz); |
| 63 | if (sz >= sizeof(kb)) |
| 64 | p = buf; |
| 65 | else { |
| 66 | memcpy(kb, buf, sz); |
| 67 | memset(kb + sz, 0, sizeof(kb) - sz); |
| 68 | p = kb; |
| 69 | } |
| 70 | |
| 71 | k->k[0] = LOAD32(p + 0); k->k[1] = LOAD32(p + 4); |
| 72 | k->k[2] = LOAD32(p + 8); k->k[3] = LOAD32(p + 12); |
| 73 | k->r = 32; |
| 74 | |
| 75 | if (p == kb) |
| 76 | BURN(kb); |
| 77 | } |
| 78 | |
| 79 | /* --- @xtea_eblk@, @xtea_dblk@ --- * |
| 80 | * |
| 81 | * Arguments: @const xtea_ctx *k@ = pointer to key block |
| 82 | * @const uint32 s[2]@ = pointer to source block |
| 83 | * @uint32 d[2]@ = pointer to xteatination block |
| 84 | * |
| 85 | * Returns: --- |
| 86 | * |
| 87 | * Use: Low-level block encryption and decryption. |
| 88 | */ |
| 89 | |
| 90 | #define DELTA 0x9e3779b9 |
| 91 | |
| 92 | void xtea_eblk(const xtea_ctx *k, const uint32 *s, uint32 *d) |
| 93 | { |
| 94 | uint32 y = s[0], z = s[1]; |
| 95 | uint32 n = 0; |
| 96 | unsigned i; |
| 97 | |
| 98 | for (i = 0; i < k->r; i++) { |
| 99 | y = U32(y + ((((z << 4) ^ (z >> 5)) + z) ^ (n + k->k[n & 3]))); |
| 100 | n += DELTA; |
| 101 | z = U32(z + ((((y << 4) ^ (y >> 5)) + y) ^ (n + k->k[(n >> 11) & 3]))); |
| 102 | } |
| 103 | d[0] = y; d[1] = z; |
| 104 | } |
| 105 | |
| 106 | void xtea_dblk(const xtea_ctx *k, const uint32 *s, uint32 *d) |
| 107 | { |
| 108 | uint32 y = s[0], z = s[1]; |
| 109 | uint32 n = DELTA * k->r; |
| 110 | unsigned i; |
| 111 | |
| 112 | for (i = 0; i < k->r; i++) { |
| 113 | z = U32(z - ((((y << 4) ^ (y >> 5)) + y) ^ (n + k->k[(n >> 11) & 3]))); |
| 114 | n -= DELTA; |
| 115 | y = U32(y - ((((z << 4) ^ (z >> 5)) + z) ^ (n + k->k[n & 3]))); |
| 116 | } |
| 117 | d[0] = y; d[1] = z; |
| 118 | } |
| 119 | |
| 120 | BLKC_TEST(XTEA, xtea) |
| 121 | |
| 122 | /*----- That's all, folks -------------------------------------------------*/ |