2 * Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
10 #include "internal/ffc.h"
13 * SP800-56Ar3 5.6.1.1.4 Key pair generation by testing candidates.
14 * Generates a private key in the interval [1, min(2 ^ N - 1, q - 1)].
16 * ctx must be set up with a libctx (for fips mode).
17 * params contains the FFC domain parameters p, q and g (for DH or DSA).
18 * N is the maximum bit length of the generated private key,
19 * s is the security strength.
20 * priv_key is the returned private key,
22 int ffc_generate_private_key(BN_CTX *ctx, const FFC_PARAMS *params,
23 int N, int s, BIGNUM *priv)
27 BIGNUM *m, *two_powN = NULL;
29 /* Step (2) : check range of N */
30 if (N < 2 * s || N > BN_num_bits(params->q))
35 if (two_powN == NULL || !BN_lshift(two_powN, BN_value_one(), N))
38 /* Step (5) : M = min(2 ^ N, q) */
39 m = (BN_cmp(two_powN, params->q) > 0) ? params->q : two_powN;
41 /* Steps (3, 4 & 7) : c + 1 = 1 + random[0..2^N - 1] */
42 if (!BN_priv_rand_range_ex(priv, two_powN, ctx)
43 || !BN_add_word(priv, 1))
45 /* Step (6) : loop if c > M - 2 (i.e. c + 1 >= M) */
46 if (BN_cmp(priv, m) < 0)
56 if (!BN_priv_rand_range_ex(priv, params->q, ctx))
58 } while (BN_is_zero(priv) || BN_is_one(priv));
60 #endif /* FIPS_MODE */