4 * This file is part of BeRTOS.
6 * Bertos is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 * As a special exception, you may use this file as part of a free software
21 * library without restriction. Specifically, if other files instantiate
22 * templates or use macros or inline functions from this file, or you compile
23 * this file and link it with other files to produce an executable, this
24 * file does not by itself cause the resulting executable to be covered by
25 * the GNU General Public License. This exception does not however
26 * invalidate any other reasons why the executable file might be covered by
27 * the GNU General Public License.
29 * Copyright 2010 Develer S.r.l. (http://www.develer.com/)
33 * \brief ANSI X9.17 PRNG implementation
34 * \author Giovanni Bajo <rasky@develer.com>
40 #include <drv/timer.h>
41 #include "hw/hw_timer.h"
43 static void x917_next(X917Context *ctx, BlockCipher *cipher, uint8_t *out)
45 const size_t blen = cipher_block_len(cipher);
57 ASSERT(sizeof(DT.bytes) >= sizeof(ticks_t) + sizeof(hptime_t));
59 DT.data.t0 = timer_clock();
60 DT.data.t1 = timer_hw_hpread();
62 cipher_ecb_encrypt(cipher, DT.bytes);
64 xor_block(out, DT.bytes, ctx->state, blen);
65 cipher_ecb_encrypt(cipher, out);
67 xor_block(ctx->state, DT.bytes, out, blen);
68 cipher_ecb_encrypt(cipher, ctx->state);
74 static void x917_generate(PRNG *ctx_, uint8_t *data, size_t len)
76 X917Context *ctx = (X917Context *)ctx_;
77 BlockCipher *cipher = AES128_stackinit();
79 const size_t blen = cipher_block_len(cipher);
83 ASSERT(sizeof(ctx->state) >= blen);
84 ASSERT(sizeof(ctx->key) >= cipher_key_len(cipher));
86 cipher_set_key(cipher, ctx->key);
90 size_t L = MIN(blen, len);
91 x917_next(ctx, cipher, temp);
92 memcpy(data, temp, L);
98 static void x917_reseed(PRNG *ctx_, const uint8_t *seed)
100 // The X9.17 standard does not specify reseeding. To avoid external
101 // dependencies, we implement it this way:
102 // * Generate a new random block, xor it with the first part
103 // of the seed, and use the result as new seed.
104 // * Generate and throw away a block to update the state.
105 X917Context *ctx = (X917Context *)ctx_;
107 size_t klen = sizeof(ctx->key);
108 size_t blen = sizeof(ctx->state);
111 x917_generate(ctx_, buf, klen);
113 xor_block(ctx->key, buf, seed, klen);
114 xor_block(ctx->state, ctx->state, seed+klen, blen);
119 /*********************************************************************/
121 void x917_init(X917Context *ctx)
123 ctx->rng.reseed = x917_reseed;
124 ctx->rng.generate = x917_generate;
125 ctx->rng.seed_len = sizeof(ctx->key) + sizeof(ctx->state);