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/* 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.h"
/**
@file dsa_generate_pqg.c
DSA implementation - generate DSA parameters p, q & g
*/
#ifdef LTC_MDSA
/**
Create DSA parameters (INTERNAL ONLY, not part of public API)
@param prng An active PRNG state
@param wprng The index of the PRNG desired
@param group_size Size of the multiplicative group (octets)
@param modulus_size Size of the modulus (octets)
@param p [out] bignum where generated 'p' is stored (must be initialized by caller)
@param q [out] bignum where generated 'q' is stored (must be initialized by caller)
@param g [out] bignum where generated 'g' is stored (must be initialized by caller)
@return CRYPT_OK if successful, upon error this function will free all allocated memory
*/
static int _dsa_make_params(prng_state *prng, int wprng, int group_size, int modulus_size, void *p, void *q, void *g)
{
unsigned long L, N, n, outbytes, seedbytes, counter, j, i;
int err, res, mr_tests_q, mr_tests_p, found_p, found_q, hash;
unsigned char *wbuf, *sbuf, digest[MAXBLOCKSIZE];
void *t2L1, *t2N1, *t2q, *t2seedlen, *U, *W, *X, *c, *h, *e, *seedinc;
/* check size */
if (group_size >= LTC_MDSA_MAX_GROUP || group_size < 1 || group_size >= modulus_size) {
return CRYPT_INVALID_ARG;
}
/* FIPS-186-4 A.1.1.2 Generation of the Probable Primes p and q Using an Approved Hash Function
*
* L = The desired length of the prime p (in bits e.g. L = 1024)
* N = The desired length of the prime q (in bits e.g. N = 160)
* seedlen = The desired bit length of the domain parameter seed; seedlen shallbe equal to or greater than N
* outlen = The bit length of Hash function
*
* 1. Check that the (L, N)
* 2. If (seedlen <N), then return INVALID.
* 3. n = ceil(L / outlen) - 1
* 4. b = L- 1 - (n * outlen)
* 5. domain_parameter_seed = an arbitrary sequence of seedlen bits
* 6. U = Hash (domain_parameter_seed) mod 2^(N-1)
* 7. q = 2^(N-1) + U + 1 - (U mod 2)
* 8. Test whether or not q is prime as specified in Appendix C.3
* 9. If qis not a prime, then go to step 5.
* 10. offset = 1
* 11. For counter = 0 to (4L- 1) do {
* For j=0 to n do {
* Vj = Hash ((domain_parameter_seed+ offset + j) mod 2^seedlen
* }
* W = V0 + (V1 *2^outlen) + ... + (Vn-1 * 2^((n-1) * outlen)) + ((Vn mod 2^b) * 2^(n * outlen))
* X = W + 2^(L-1) Comment: 0 <= W < 2^(L-1); hence 2^(L-1) <= X < 2^L
* c = X mod 2*q
* p = X - (c - 1) Comment: p ~ 1 (mod 2*q)
* If (p >= 2^(L-1)) {
* Test whether or not p is prime as specified in Appendix C.3.
* If p is determined to be prime, then return VALID and the values of p, qand (optionally) the values of domain_parameter_seed and counter
* }
* offset = offset + n + 1 Comment: Increment offset
* }
*/
seedbytes = group_size;
L = (unsigned long)modulus_size * 8;
N = (unsigned long)group_size * 8;
/* XXX-TODO no Lucas test */
#ifdef LTC_MPI_HAS_LUCAS_TEST
/* M-R tests (when followed by one Lucas test) according FIPS-186-4 - Appendix C.3 - table C.1 */
mr_tests_p = (L <= 2048) ? 3 : 2;
if (N <= 160) { mr_tests_q = 19; }
else if (N <= 224) { mr_tests_q = 24; }
else { mr_tests_q = 27; }
#else
/* M-R tests (without Lucas test) according FIPS-186-4 - Appendix C.3 - table C.1 */
if (L <= 1024) { mr_tests_p = 40; }
else if (L <= 2048) { mr_tests_p = 56; }
else { mr_tests_p = 64; }
if (N <= 160) { mr_tests_q = 40; }
else if (N <= 224) { mr_tests_q = 56; }
else { mr_tests_q = 64; }
#endif
if (N <= 256) {
hash = register_hash(&sha256_desc);
}
else if (N <= 384) {
hash = register_hash(&sha384_desc);
}
else if (N <= 512) {
hash = register_hash(&sha512_desc);
}
else {
return CRYPT_INVALID_ARG; /* group_size too big */
}
if ((err = hash_is_valid(hash)) != CRYPT_OK) { return err; }
outbytes = hash_descriptor[hash].hashsize;
n = ((L + outbytes*8 - 1) / (outbytes*8)) - 1;
if ((wbuf = XMALLOC((n+1)*outbytes)) == NULL) { err = CRYPT_MEM; goto cleanup3; }
if ((sbuf = XMALLOC(seedbytes)) == NULL) { err = CRYPT_MEM; goto cleanup2; }
err = mp_init_multi(&t2L1, &t2N1, &t2q, &t2seedlen, &U, &W, &X, &c, &h, &e, &seedinc, NULL);
if (err != CRYPT_OK) { goto cleanup1; }
if ((err = mp_2expt(t2L1, L-1)) != CRYPT_OK) { goto cleanup; }
/* t2L1 = 2^(L-1) */
if ((err = mp_2expt(t2N1, N-1)) != CRYPT_OK) { goto cleanup; }
/* t2N1 = 2^(N-1) */
if ((err = mp_2expt(t2seedlen, seedbytes*8)) != CRYPT_OK) { goto cleanup; }
/* t2seedlen = 2^seedlen */
for(found_p=0; !found_p;) {
/* q */
for(found_q=0; !found_q;) {
if (prng_descriptor[wprng].read(sbuf, seedbytes, prng) != seedbytes) { err = CRYPT_ERROR_READPRNG; goto cleanup; }
i = outbytes;
if ((err = hash_memory(hash, sbuf, seedbytes, digest, &i)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_read_unsigned_bin(U, digest, outbytes)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mod(U, t2N1, U)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_add(t2N1, U, q)) != CRYPT_OK) { goto cleanup; }
if (!mp_isodd(q)) mp_add_d(q, 1, q);
if ((err = mp_prime_is_prime(q, mr_tests_q, &res)) != CRYPT_OK) { goto cleanup; }
if (res == LTC_MP_YES) found_q = 1;
}
/* p */
if ((err = mp_read_unsigned_bin(seedinc, sbuf, seedbytes)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_add(q, q, t2q)) != CRYPT_OK) { goto cleanup; }
for(counter=0; counter < 4*L && !found_p; counter++) {
for(j=0; j<=n; j++) {
if ((err = mp_add_d(seedinc, 1, seedinc)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mod(seedinc, t2seedlen, seedinc)) != CRYPT_OK) { goto cleanup; }
/* seedinc = (seedinc+1) % 2^seed_bitlen */
if ((i = mp_unsigned_bin_size(seedinc)) > seedbytes) { err = CRYPT_INVALID_ARG; goto cleanup; }
zeromem(sbuf, seedbytes);
if ((err = mp_to_unsigned_bin(seedinc, sbuf + seedbytes-i)) != CRYPT_OK) { goto cleanup; }
i = outbytes;
err = hash_memory(hash, sbuf, seedbytes, wbuf+(n-j)*outbytes, &i);
if (err != CRYPT_OK) { goto cleanup; }
}
if ((err = mp_read_unsigned_bin(W, wbuf, (n+1)*outbytes)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mod(W, t2L1, W)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_add(W, t2L1, X)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mod(X, t2q, c)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_sub_d(c, 1, p)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_sub(X, p, p)) != CRYPT_OK) { goto cleanup; }
if (mp_cmp(p, t2L1) != LTC_MP_LT) {
/* p >= 2^(L-1) */
if ((err = mp_prime_is_prime(p, mr_tests_p, &res)) != CRYPT_OK) { goto cleanup; }
if (res == LTC_MP_YES) {
found_p = 1;
}
}
}
}
/* FIPS-186-4 A.2.1 Unverifiable Generation of the Generator g
* 1. e = (p - 1)/q
* 2. h = any integer satisfying: 1 < h < (p - 1)
* h could be obtained from a random number generator or from a counter that changes after each use
* 3. g = h^e mod p
* 4. if (g == 1), then go to step 2.
*
*/
if ((err = mp_sub_d(p, 1, e)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_div(e, q, e, c)) != CRYPT_OK) { goto cleanup; }
/* e = (p - 1)/q */
i = mp_count_bits(p);
do {
do {
if ((err = rand_bn_bits(h, i, prng, wprng)) != CRYPT_OK) { goto cleanup; }
} while (mp_cmp(h, p) != LTC_MP_LT || mp_cmp_d(h, 2) != LTC_MP_GT);
if ((err = mp_sub_d(h, 1, h)) != CRYPT_OK) { goto cleanup; }
/* h is randon and 1 < h < (p-1) */
if ((err = mp_exptmod(h, e, p, g)) != CRYPT_OK) { goto cleanup; }
} while (mp_cmp_d(g, 1) == LTC_MP_EQ);
err = CRYPT_OK;
cleanup:
mp_clear_multi(t2L1, t2N1, t2q, t2seedlen, U, W, X, c, h, e, seedinc, NULL);
cleanup1:
XFREE(sbuf);
cleanup2:
XFREE(wbuf);
cleanup3:
return err;
}
/**
Generate DSA parameters p, q & g
@param prng An active PRNG state
@param wprng The index of the PRNG desired
@param group_size Size of the multiplicative group (octets)
@param modulus_size Size of the modulus (octets)
@param key [out] Where to store the created key
@return CRYPT_OK if successful.
*/
int dsa_generate_pqg(prng_state *prng, int wprng, int group_size, int modulus_size, dsa_key *key)
{
int err;
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(ltc_mp.name != NULL);
/* init mp_ints */
if ((err = mp_init_multi(&key->p, &key->g, &key->q, &key->x, &key->y, NULL)) != CRYPT_OK) {
return err;
}
/* generate params */
err = _dsa_make_params(prng, wprng, group_size, modulus_size, key->p, key->q, key->g);
if (err != CRYPT_OK) {
goto cleanup;
}
key->qord = group_size;
return CRYPT_OK;
cleanup:
dsa_free(key);
return err;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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