| // SPDX-License-Identifier: BSD-2-Clause |
| /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
| * |
| * LibTomCrypt is a library that provides various cryptographic |
| * algorithms in a highly modular and flexible manner. |
| * |
| * The library is free for all purposes without any express |
| * guarantee it works. |
| */ |
| |
| #include "tomcrypt_private.h" |
| |
| #ifdef LTC_MDH |
| |
| static int _dh_groupsize_to_keysize(int groupsize) |
| { |
| /* The strength estimates from https://tools.ietf.org/html/rfc3526#section-8 |
| * We use "Estimate 2" to get an appropriate private key (exponent) size. |
| */ |
| if (groupsize <= 0) { |
| return 0; |
| } |
| if (groupsize <= 192) { |
| return 30; /* 1536-bit => key size 240-bit */ |
| } |
| if (groupsize <= 256) { |
| return 40; /* 2048-bit => key size 320-bit */ |
| } |
| if (groupsize <= 384) { |
| return 52; /* 3072-bit => key size 416-bit */ |
| } |
| if (groupsize <= 512) { |
| return 60; /* 4096-bit => key size 480-bit */ |
| } |
| if (groupsize <= 768) { |
| return 67; /* 6144-bit => key size 536-bit */ |
| } |
| if (groupsize <= 1024) { |
| return 77; /* 8192-bit => key size 616-bit */ |
| } |
| return 0; |
| } |
| |
| int dh_generate_key(prng_state *prng, int wprng, dh_key *key) |
| { |
| unsigned char *buf; |
| unsigned long keysize; |
| int err, max_iterations = LTC_PK_MAX_RETRIES; |
| |
| LTC_ARGCHK(key != NULL); |
| LTC_ARGCHK(ltc_mp.name != NULL); |
| |
| /* good prng? */ |
| if ((err = prng_is_valid(wprng)) != CRYPT_OK) { |
| return err; |
| } |
| |
| keysize = _dh_groupsize_to_keysize(mp_unsigned_bin_size(key->prime)); |
| if (keysize == 0) { |
| err = CRYPT_INVALID_KEYSIZE; |
| goto freemp; |
| } |
| |
| /* allocate buffer */ |
| buf = XMALLOC(keysize); |
| if (buf == NULL) { |
| err = CRYPT_MEM; |
| goto freemp; |
| } |
| |
| key->type = PK_PRIVATE; |
| do { |
| /* make up random buf */ |
| if (prng_descriptor[wprng]->read(buf, keysize, prng) != keysize) { |
| err = CRYPT_ERROR_READPRNG; |
| goto freebuf; |
| } |
| /* load the x value - private key */ |
| if ((err = mp_read_unsigned_bin(key->x, buf, keysize)) != CRYPT_OK) { |
| goto freebuf; |
| } |
| /* compute the y value - public key */ |
| if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) { |
| goto freebuf; |
| } |
| err = dh_check_pubkey(key); |
| } while (err != CRYPT_OK && max_iterations-- > 0); |
| |
| freebuf: |
| zeromem(buf, keysize); |
| XFREE(buf); |
| freemp: |
| if (err != CRYPT_OK) dh_free(key); |
| return err; |
| } |
| |
| #endif /* LTC_MDH */ |
| |
| /* ref: $Format:%D$ */ |
| /* git commit: $Format:%H$ */ |
| /* commit time: $Format:%ai$ */ |