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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: xtea.c,v 1.3 2004/04/08 01:36:15 mdw Exp $ |
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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 | |
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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 | |
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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; |
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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 | |
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98 | for (i = 0; i < k->r; i++) { |
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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]; |
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109 | uint32 n = DELTA * k->r; |
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110 | unsigned i; |
111 | |
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112 | for (i = 0; i < k->r; i++) { |
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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 -------------------------------------------------*/ |