| // 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 |
| |
| /** |
| Check DH public key (INTERNAL ONLY, not part of public API) |
| @param key The key you wish to test |
| @return CRYPT_OK if successful |
| */ |
| int dh_check_pubkey(const dh_key *key) |
| { |
| void *p_minus1; |
| ltc_mp_digit digit; |
| int i, digit_count, bits_set = 0, err; |
| |
| LTC_ARGCHK(key != NULL); |
| |
| if ((err = mp_init(&p_minus1)) != CRYPT_OK) { |
| return err; |
| } |
| |
| /* avoid: y <= 1 OR y >= p-1 */ |
| if ((err = mp_sub_d(key->prime, 1, p_minus1)) != CRYPT_OK) { |
| goto error; |
| } |
| if (mp_cmp(key->y, p_minus1) != LTC_MP_LT || mp_cmp_d(key->y, 1) != LTC_MP_GT) { |
| err = CRYPT_INVALID_ARG; |
| goto error; |
| } |
| |
| /* public key must have more than one bit set */ |
| digit_count = mp_get_digit_count(key->y); |
| for (i = 0; i < digit_count && bits_set < 2; i++) { |
| digit = mp_get_digit(key->y, i); |
| while (digit > 0) { |
| if (digit & 1) bits_set++; |
| digit >>= 1; |
| } |
| } |
| if (bits_set > 1) { |
| err = CRYPT_OK; |
| } |
| else { |
| err = CRYPT_INVALID_ARG; |
| } |
| |
| error: |
| mp_clear(p_minus1); |
| return err; |
| } |
| |
| #endif /* LTC_MDH */ |
| |
| /* ref: $Format:%D$ */ |
| /* git commit: $Format:%H$ */ |
| /* commit time: $Format:%ai$ */ |