d03ab969 |
1 | /* -*-c-*- |
2 | * |
3 | * $Id: idea.c,v 1.1 1999/09/03 08:41:12 mdw Exp $ |
4 | * |
5 | * Implementation of the IDEA cipher |
6 | * |
7 | * (c) 1999 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 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: idea.c,v $ |
33 | * Revision 1.1 1999/09/03 08:41:12 mdw |
34 | * Initial import. |
35 | * |
36 | */ |
37 | |
38 | /*----- Header files ------------------------------------------------------*/ |
39 | |
40 | #include <assert.h> |
41 | #include <stdio.h> |
42 | #include <stdlib.h> |
43 | #include <string.h> |
44 | |
45 | #include <mLib/bits.h> |
46 | |
47 | #include "blkc.h" |
48 | #include "idea.h" |
49 | |
50 | /*----- Main code ---------------------------------------------------------*/ |
51 | |
52 | /* --- @inv@ --- * |
53 | * |
54 | * Arguments: @uint16 n@ = number to invert |
55 | * |
56 | * Returns: Multiplicative inverse of @n@ %$\pmod{2^{16} + 1}$%. |
57 | * |
58 | * Use: Computes multiplicative inverses. This is handy for the |
59 | * decryption key scheduling. |
60 | */ |
61 | |
62 | static uint16 inv(uint16 n) |
63 | { |
64 | uint32 m = 0x10001; |
65 | uint32 a = 1, b = 0; |
66 | |
67 | for (;;) { |
68 | uint32 q, r, t; |
69 | if (!(r = m % n)) |
70 | break; |
71 | q = m / n; |
72 | m = n; n = r; |
73 | t = a; a = b - q * a; b = t; |
74 | } |
75 | if (a > MASK16) |
76 | a += 1; |
77 | return (U16(a)); |
78 | } |
79 | |
80 | /* --- @MUL@ --- * |
81 | * |
82 | * Arguments @x@ and @y@ are two 32-bit values to multiply. On exit, @x@ is |
83 | * the product of the two arguments. The result is not normalized back to 16 |
84 | * bits; the arguments are not expected to be normalized. |
85 | */ |
86 | |
87 | #define MUL(x, y) do { \ |
88 | uint32 _mx, _my = (y); \ |
89 | if ((_mx = U16(x)) == 0) \ |
90 | (x) = 1 - _my; \ |
91 | else if (_my == 0) \ |
92 | (x) = 1 - _mx; \ |
93 | else { \ |
94 | _my *= _mx; \ |
95 | _mx = U16(_my); _my >>= 16; \ |
96 | if (_mx < _my) \ |
97 | (x) = _mx - _my + 1; \ |
98 | else \ |
99 | (x) = _mx - _my; \ |
100 | } \ |
101 | } while (0) |
102 | |
103 | /* --- @idea_init@ --- * |
104 | * |
105 | * Arguments: @idea_ctx *k@ = pointer to key block |
106 | * @const void *buf@ = pointer to key buffer |
107 | * @size_t sz@ = size of key material |
108 | * |
109 | * Returns: --- |
110 | * |
111 | * Use: Initializes an IDEA key buffer. The buffer must be exactly |
112 | * 16 bytes in size, because IDEA is only defined with a key |
113 | * size of 128 bits. |
114 | */ |
115 | |
116 | void idea_init(idea_ctx *k, const void *buf, size_t sz) |
117 | { |
118 | assert(((void)"IDEA key must be 128 bits", sz == IDEA_KEYSZ)); |
119 | |
120 | /* --- Unpack the encryption key --- */ |
121 | |
122 | { |
123 | const octet *p = buf; |
124 | uint16 *q = k->e; |
125 | uint32 a = LOAD32(p + 0); |
126 | uint32 b = LOAD32(p + 4); |
127 | uint32 c = LOAD32(p + 8); |
128 | uint32 d = LOAD32(p + 12); |
129 | int i; |
130 | |
131 | /* --- Main unpacking loop --- */ |
132 | |
133 | for (i = 0; i < 6; i++) { |
134 | |
135 | /* --- Spit out the next 8 subkeys --- */ |
136 | |
137 | q[0] = U16(a >> 16); |
138 | q[1] = U16(a >> 0); |
139 | q[2] = U16(b >> 16); |
140 | q[3] = U16(b >> 0); |
141 | q[4] = U16(c >> 16); |
142 | q[5] = U16(c >> 0); |
143 | q[6] = U16(d >> 16); |
144 | q[7] = U16(d >> 0); |
145 | q += 8; |
146 | |
147 | /* --- Rotate and permute the subkeys --- */ |
148 | |
149 | { |
150 | uint32 t = a; |
151 | a = U32((a << 25) | (b >> 7)); |
152 | b = U32((b << 25) | (c >> 7)); |
153 | c = U32((c << 25) | (d >> 7)); |
154 | d = U32((d << 25) | (t >> 7)); |
155 | } |
156 | } |
157 | |
158 | /* --- Write out the tail-enders --- */ |
159 | |
160 | q[0] = U16(a >> 16); |
161 | q[1] = U16(a >> 0); |
162 | q[2] = U16(b >> 16); |
163 | q[3] = U16(b >> 0); |
164 | } |
165 | |
166 | /* --- Convert this into the decryption key --- */ |
167 | |
168 | { |
169 | uint16 *p = k->e + 52; |
170 | uint16 *q = k->d; |
171 | int i; |
172 | |
173 | /* --- Translate the main round keys --- */ |
174 | |
175 | for (i = 0; i < 8; i++) { |
176 | p -= 6; |
177 | q[4] = p[0]; |
178 | q[5] = p[1]; |
179 | q[0] = inv(p[2]); |
180 | q[3] = inv(p[5]); |
181 | if (i) { |
182 | q[1] = 0x10000 - p[4]; |
183 | q[2] = 0x10000 - p[3]; |
184 | } else { |
185 | q[1] = 0x10000 - p[3]; |
186 | q[2] = 0x10000 - p[4]; |
187 | } |
188 | q += 6; |
189 | } |
190 | |
191 | /* --- Translate the tail-enders --- */ |
192 | |
193 | p -= 4; |
194 | q[0] = inv(p[0]); |
195 | q[1] = 0x10000 - p[1]; |
196 | q[2] = 0x10000 - p[2]; |
197 | q[3] = inv(p[3]); |
198 | } |
199 | } |
200 | |
201 | /* --- @ROUND@ --- */ |
202 | |
203 | #define MIX(k, a, b, c, d) do { \ |
204 | MUL(a, (k)[0]); \ |
205 | (b) += (k)[1]; \ |
206 | (c) += (k)[2]; \ |
207 | MUL(d, (k)[3]); \ |
208 | } while (0) |
209 | |
210 | #define MA(k, a, b, c, d) do { \ |
211 | unsigned _u = (a) ^ (c); \ |
212 | unsigned _v = (b) ^ (d); \ |
213 | MUL(_u, (k)[4]); \ |
214 | _v += _u; \ |
215 | MUL(_v, (k)[5]); \ |
216 | _u += _v; \ |
217 | (a) ^= _v; \ |
218 | (b) ^= _u; \ |
219 | (c) ^= _v; \ |
220 | (d) ^= _u; \ |
221 | } while (0); |
222 | |
223 | #define ROUND(k, a, b, c, d) do { \ |
224 | MIX((k), (a), (b), (c), (d)); \ |
225 | MA((k), (a), (b), (c), (d)); \ |
226 | (k) += 6; \ |
227 | } while (0) |
228 | |
229 | /* --- Encryption --- */ |
230 | |
231 | #define EBLK(k, a, b, c, d) do { \ |
232 | unsigned _a = U16(a >> 16); \ |
233 | unsigned _b = U16(a >> 0); \ |
234 | unsigned _c = U16(b >> 16); \ |
235 | unsigned _d = U16(b >> 0); \ |
236 | const uint16 *_k = (k); \ |
237 | \ |
238 | ROUND(_k, _a, _b, _c, _d); \ |
239 | ROUND(_k, _a, _c, _b, _d); \ |
240 | ROUND(_k, _a, _b, _c, _d); \ |
241 | ROUND(_k, _a, _c, _b, _d); \ |
242 | ROUND(_k, _a, _b, _c, _d); \ |
243 | ROUND(_k, _a, _c, _b, _d); \ |
244 | ROUND(_k, _a, _b, _c, _d); \ |
245 | ROUND(_k, _a, _c, _b, _d); \ |
246 | MIX (_k, _a, _c, _b, _d); \ |
247 | (c) = (U16(_a) << 16) | U16(_c); \ |
248 | (d) = (U16(_b) << 16) | U16(_d); \ |
249 | } while (0) |
250 | |
251 | #define DBLK(k, a, b) EBLK((k), (a), (b)) |
252 | |
253 | /* --- @idea_eblk@, @idea_dblk@ --- * |
254 | * |
255 | * Arguments: @const idea_ctx *k@ = pointer to a key block |
256 | * @const uint32 s[2]@ = pointer to source block |
257 | * @uint32 d[2]@ = pointer to destination block |
258 | * |
259 | * Returns: --- |
260 | * |
261 | * Use: Low-level block encryption and decryption. |
262 | */ |
263 | |
264 | void idea_eblk(const idea_ctx *k, const uint32 *s, uint32 *d) |
265 | { |
266 | EBLK(k->e, s[0], s[1], d[0], d[1]); |
267 | } |
268 | |
269 | void idea_dblk(const idea_ctx *k, const uint32 *s, uint32 *d) |
270 | { |
271 | EBLK(k->d, s[0], s[1], d[0], d[1]); |
272 | } |
273 | |
274 | BLKC_TEST(IDEA, idea) |
275 | |
276 | /*----- That's all, folks -------------------------------------------------*/ |