crypto/ffc/ffc_key_generate.c

   1 /*
   2  * Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   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
   8  */
   9
  10 #include "internal/ffc.h"
  11
  12 /*
  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)].
  15  *
  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,
  21  */
  22 int ffc_generate_private_key(BN_CTX *ctx, const FFC_PARAMS *params,
  23                              int N, int s, BIGNUM *priv)
  24 {
  25 #ifdef FIPS_MODE
  26     return ffc_generate_private_key_fips(ctx, params, N, s, priv);
  27 #else
  28     do {
  29         if (!BN_priv_rand_range_ex(priv, params->q, ctx))
  30             return 0;
  31     } while (BN_is_zero(priv) || BN_is_one(priv));
  32     return 1;
  33 #endif /* FIPS_MODE */
  34 }
  35
  36 int ffc_generate_private_key_fips(BN_CTX *ctx, const FFC_PARAMS *params,
  37                                   int N, int s, BIGNUM *priv)
  38 {
  39     int ret = 0, qbits = BN_num_bits(params->q);
  40     BIGNUM *m, *two_powN = NULL;
  41
  42     /* Step (2) : check range of N */
  43     if (N < 2 * s || N > qbits)
  44         return 0;
  45
  46     /* Deal with the edge case where the value of N is not set */
  47     if (N == 0) {
  48         N = qbits;
  49         s = N / 2;
  50     }
  51
  52     two_powN = BN_new();
  53     /* 2^N */
  54     if (two_powN == NULL || !BN_lshift(two_powN, BN_value_one(), N))
  55         goto err;
  56
  57     /* Step (5) : M = min(2 ^ N, q) */
  58     m = (BN_cmp(two_powN, params->q) > 0) ? params->q : two_powN;
  59
  60     do {
  61         /* Steps (3, 4 & 7) :  c + 1 = 1 + random[0..2^N - 1] */
  62         if (!BN_priv_rand_range_ex(priv, two_powN, ctx)
  63             || !BN_add_word(priv, 1))
  64             goto err;
  65         /* Step (6) : loop if c > M - 2 (i.e. c + 1 >= M) */
  66         if (BN_cmp(priv, m) < 0)
  67             break;
  68     } while (1);
  69
  70     ret = 1;
  71 err:
  72     BN_free(two_powN);
  73     return ret;
  74 }