Home | History | Annotate | Line # | Download | only in ffc 
      1 /*
      2  * Copyright 2019-2021 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 ossl_ffc_generate_private_key(BN_CTX *ctx, const FFC_PARAMS *params,
     23     int N, int s, BIGNUM *priv)
     24 {
     25     int ret = 0, qbits = BN_num_bits(params->q);
     26     BIGNUM *m, *two_powN = NULL;
     27 
     28     /* Deal with the edge cases where the value of N and/or s is not set */
     29     if (s == 0)
     30         goto err;
     31     if (N == 0)
     32         N = params->keylength ? params->keylength : 2 * s;
     33 
     34     /* Step (2) : check range of N */
     35     if (N < 2 * s || N > qbits)
     36         return 0;
     37 
     38     two_powN = BN_new();
     39     /* 2^N */
     40     if (two_powN == NULL || !BN_lshift(two_powN, BN_value_one(), N))
     41         goto err;
     42 
     43     /* Step (5) : M = min(2 ^ N, q) */
     44     m = (BN_cmp(two_powN, params->q) > 0) ? params->q : two_powN;
     45 
     46     do {
     47         /* Steps (3, 4 & 7) :  c + 1 = 1 + random[0..2^N - 1] */
     48         if (!BN_priv_rand_range_ex(priv, two_powN, 0, ctx)
     49             || !BN_add_word(priv, 1))
     50             goto err;
     51         /* Step (6) : loop if c > M - 2 (i.e. c + 1 >= M) */
     52         if (BN_cmp(priv, m) < 0)
     53             break;
     54     } while (1);
     55 
     56     ret = 1;
     57 err:
     58     BN_free(two_powN);
     59     return ret;
     60 }
     61