/**
Create a DSA key (with given params)
@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
@param p_hex Hexadecimal string 'p'
@param q_hex Hexadecimal string 'q'
@param g_hex Hexadecimal string 'g'
@return CRYPT_OK if successful, upon error this function will free all allocated memory
*/
static int dsa_make_key_ex(prng_state *prng, int wprng, int group_size, int modulus_size, dsa_key *key, char* p_hex, char* q_hex, char* g_hex)
{
int err, qbits;
LTC_ARGCHK(key != NULL);
/* init mp_ints */
if ((err = mp_init_multi(&key->g, &key->q, &key->p, &key->x, &key->y, NULL)) != CRYPT_OK) {
return err;
}
if (p_hex == NULL || q_hex == NULL || g_hex == NULL) {
/* generate params */
err = dsa_make_params(prng, wprng, group_size, modulus_size, key->p, key->q, key->g);
if (err != CRYPT_OK) { goto cleanup; }
}
else {
/* read params */
if ((err = mp_read_radix(key->p, p_hex, 16)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_read_radix(key->q, q_hex, 16)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_read_radix(key->g, g_hex, 16)) != CRYPT_OK) { goto cleanup; }
/* XXX-TODO maybe do some validity check for p, q, g */
}
/* so now we have our DH structure, generator g, order q, modulus p
Now we need a random exponent [mod q] and it's power g^x mod p
*/
qbits = mp_count_bits(key->q);
do {
if ((err = rand_bn_bits(key->x, qbits, prng, wprng)) != CRYPT_OK) { goto cleanup; }
/* private key x should be from range: 1 <= x <= q-1 (see FIPS 186-4 B.1.2) */
} while (mp_cmp_d(key->x, 0) != LTC_MP_GT || mp_cmp(key->x, key->q) != LTC_MP_LT);
if ((err = mp_exptmod(key->g, key->x, key->p, key->y)) != CRYPT_OK) { goto cleanup; }
key->type = PK_PRIVATE;
key->qord = group_size;
return CRYPT_OK;
cleanup:
mp_clear_multi(key->g, key->q, key->p, key->x, key->y, NULL);
return err;
}
/**
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;
}
int ecc_make_key_ex(prng_state *prng, int wprng, ecc_key *key, const ltc_ecc_set_type *dp)
{
int err;
ecc_point *base;
void *prime, *order, *a;
unsigned char *buf;
int keysize, orderbits;
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(ltc_mp.name != NULL);
LTC_ARGCHK(dp != NULL);
/* good prng? */
if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
return err;
}
key->idx = -1;
key->dp = dp;
keysize = dp->size;
/* allocate ram */
base = NULL;
buf = XMALLOC(ECC_MAXSIZE);
if (buf == NULL) {
return CRYPT_MEM;
}
/* make up random string */
if (prng_descriptor[wprng].read(buf, (unsigned long)keysize, prng) != (unsigned long)keysize) {
err = CRYPT_ERROR_READPRNG;
goto ERR_BUF;
}
/* setup the key variables */
if ((err = mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->pubkey.z, &key->k, &prime, &order, &a, NULL)) != CRYPT_OK) {
goto ERR_BUF;
}
base = ltc_ecc_new_point();
if (base == NULL) {
err = CRYPT_MEM;
goto errkey;
}
/* read in the specs for this key */
if ((err = mp_read_radix(prime, (char *)key->dp->prime, 16)) != CRYPT_OK) { goto errkey; }
if ((err = mp_read_radix(order, (char *)key->dp->order, 16)) != CRYPT_OK) { goto errkey; }
if ((err = mp_read_radix(base->x, (char *)key->dp->Gx, 16)) != CRYPT_OK) { goto errkey; }
if ((err = mp_read_radix(base->y, (char *)key->dp->Gy, 16)) != CRYPT_OK) { goto errkey; }
if ((err = mp_set(base->z, 1)) != CRYPT_OK) { goto errkey; }
if ((err = mp_read_unsigned_bin(key->k, (unsigned char *)buf, keysize)) != CRYPT_OK) { goto errkey; }
/* ECC key pair generation according to FIPS-186-4 (B.4.2 Key Pair Generation by Testing Candidates):
* the generated private key k should be the range [1, order–1]
* a/ N = bitlen(order)
* b/ generate N random bits and convert them into big integer k
* c/ if k not in [1, order-1] go to b/
* e/ Q = k*G
*/
orderbits = mp_count_bits(order);
do {
if ((err = rand_bn_bits(key->k, orderbits, prng, wprng)) != CRYPT_OK) { goto errkey; }
} while (mp_iszero(key->k) || mp_cmp(key->k, order) != LTC_MP_LT);
/* make the public key */
if ((err = mp_read_radix(a, (char *)key->dp->A, 16)) != CRYPT_OK) { goto errkey; }
if ((err = ltc_mp.ecc_ptmul(key->k, base, &key->pubkey, a, prime, 1)) != CRYPT_OK) { goto errkey; }
key->type = PK_PRIVATE;
/* free up ram */
err = CRYPT_OK;
goto cleanup;
errkey:
mp_clear_multi(key->pubkey.x, key->pubkey.y, key->pubkey.z, key->k, NULL);
cleanup:
ltc_ecc_del_point(base);
mp_clear_multi(prime, order, a, NULL);
ERR_BUF:
#ifdef LTC_CLEAN_STACK
zeromem(buf, ECC_MAXSIZE);
#endif
XFREE(buf);
return err;
}
/**
Encrypt a symmetric key with DSA
@param in The symmetric key you want to encrypt
@param inlen The length of the key to encrypt (octets)
@param out [out] The destination for the ciphertext
@param outlen [in/out] The max size and resulting size of the ciphertext
@param prng An active PRNG state
@param wprng The index of the PRNG you wish to use
@param hash The index of the hash you want to use
@param key The DSA key you want to encrypt to
@return CRYPT_OK if successful
*/
int dsa_encrypt_key(const unsigned char *in, unsigned long inlen,
unsigned char *out, unsigned long *outlen,
prng_state *prng, int wprng, int hash,
dsa_key *key)
{
unsigned char *expt, *skey;
void *g_pub, *g_priv;
unsigned long x, y;
int err, qbits;
LTC_ARGCHK(in != NULL);
LTC_ARGCHK(out != NULL);
LTC_ARGCHK(outlen != NULL);
LTC_ARGCHK(key != NULL);
/* check that wprng/cipher/hash are not invalid */
if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
return err;
}
if ((err = hash_is_valid(hash)) != CRYPT_OK) {
return err;
}
if (inlen > hash_descriptor[hash]->hashsize) {
return CRYPT_INVALID_HASH;
}
/* make a random key and export the public copy */
if ((err = mp_init_multi(&g_pub, &g_priv, NULL)) != CRYPT_OK) {
return err;
}
expt = XMALLOC(mp_unsigned_bin_size(key->p) + 1);
skey = XMALLOC(MAXBLOCKSIZE);
if (expt == NULL || skey == NULL) {
if (expt != NULL) {
XFREE(expt);
}
if (skey != NULL) {
XFREE(skey);
}
mp_clear_multi(g_pub, g_priv, NULL);
return CRYPT_MEM;
}
/* make a random g_priv, g_pub = g^x pair */
qbits = mp_count_bits(key->q);
do {
if ((err = rand_bn_bits(g_priv, qbits, prng, wprng)) != CRYPT_OK) {
goto LBL_ERR;
}
/* private key x should be from range: 1 <= x <= q-1 (see FIPS 186-4 B.1.2) */
} while (mp_cmp_d(g_priv, 0) != LTC_MP_GT || mp_cmp(g_priv, key->q) != LTC_MP_LT);
/* compute y */
if ((err = mp_exptmod(key->g, g_priv, key->p, g_pub)) != CRYPT_OK) {
goto LBL_ERR;
}
/* make random key */
x = mp_unsigned_bin_size(key->p) + 1;
if ((err = dsa_shared_secret(g_priv, key->y, key, expt, &x)) != CRYPT_OK) {
goto LBL_ERR;
}
y = MAXBLOCKSIZE;
if ((err = hash_memory(hash, expt, x, skey, &y)) != CRYPT_OK) {
goto LBL_ERR;
}
/* Encrypt key */
for (x = 0; x < inlen; x++) {
skey[x] ^= in[x];
}
err = der_encode_sequence_multi(out, outlen,
LTC_ASN1_OBJECT_IDENTIFIER, hash_descriptor[hash]->OIDlen, hash_descriptor[hash]->OID,
LTC_ASN1_INTEGER, 1UL, g_pub,
LTC_ASN1_OCTET_STRING, inlen, skey,
LTC_ASN1_EOL, 0UL, NULL);
LBL_ERR:
#ifdef LTC_CLEAN_STACK
/* clean up */
zeromem(expt, mp_unsigned_bin_size(key->p) + 1);
zeromem(skey, MAXBLOCKSIZE);
#endif
XFREE(skey);
XFREE(expt);
mp_clear_multi(g_pub, g_priv, NULL);
return err;
}
/**
Sign a hash with DSA
@param in The hash to sign
@param inlen The length of the hash to sign
@param r The "r" integer of the signature (caller must initialize with mp_init() first)
@param s The "s" integer of the signature (caller must initialize with mp_init() first)
@param prng An active PRNG state
@param wprng The index of the PRNG desired
@param key A private DSA key
@return CRYPT_OK if successful
*/
int dsa_sign_hash_raw(const unsigned char *in, unsigned long inlen,
void *r, void *s,
prng_state *prng, int wprng, dsa_key *key)
{
void *k, *kinv, *tmp;
unsigned char *buf;
int err, qbits;
LTC_ARGCHK(in != NULL);
LTC_ARGCHK(r != NULL);
LTC_ARGCHK(s != NULL);
LTC_ARGCHK(key != NULL);
if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
return err;
}
if (key->type != PK_PRIVATE) {
return CRYPT_PK_NOT_PRIVATE;
}
/* check group order size */
if (key->qord >= LTC_MDSA_MAX_GROUP) {
return CRYPT_INVALID_ARG;
}
buf = XMALLOC(LTC_MDSA_MAX_GROUP);
if (buf == NULL) {
return CRYPT_MEM;
}
/* Init our temps */
if ((err = mp_init_multi(&k, &kinv, &tmp, NULL)) != CRYPT_OK) { goto ERRBUF; }
qbits = mp_count_bits(key->q);
retry:
do {
/* gen random k */
if ((err = rand_bn_bits(k, qbits, prng, wprng)) != CRYPT_OK) { goto error; }
/* k should be from range: 1 <= k <= q-1 (see FIPS 186-4 B.2.2) */
if (mp_cmp_d(k, 0) != LTC_MP_GT || mp_cmp(k, key->q) != LTC_MP_LT) { goto retry; }
/* test gcd */
if ((err = mp_gcd(k, key->q, tmp)) != CRYPT_OK) { goto error; }
} while (mp_cmp_d(tmp, 1) != LTC_MP_EQ);
/* now find 1/k mod q */
if ((err = mp_invmod(k, key->q, kinv)) != CRYPT_OK) { goto error; }
/* now find r = g^k mod p mod q */
if ((err = mp_exptmod(key->g, k, key->p, r)) != CRYPT_OK) { goto error; }
if ((err = mp_mod(r, key->q, r)) != CRYPT_OK) { goto error; }
if (mp_iszero(r) == LTC_MP_YES) { goto retry; }
/* FIPS 186-4 4.6: use leftmost min(bitlen(q), bitlen(hash)) bits of 'hash'*/
inlen = MIN(inlen, (unsigned long)(key->qord));
/* now find s = (in + xr)/k mod q */
if ((err = mp_read_unsigned_bin(tmp, (unsigned char *)in, inlen)) != CRYPT_OK) { goto error; }
if ((err = mp_mul(key->x, r, s)) != CRYPT_OK) { goto error; }
if ((err = mp_add(s, tmp, s)) != CRYPT_OK) { goto error; }
if ((err = mp_mulmod(s, kinv, key->q, s)) != CRYPT_OK) { goto error; }
if (mp_iszero(s) == LTC_MP_YES) { goto retry; }
err = CRYPT_OK;
error:
mp_clear_multi(k, kinv, tmp, NULL);
ERRBUF:
#ifdef LTC_CLEAN_STACK
zeromem(buf, LTC_MDSA_MAX_GROUP);
#endif
XFREE(buf);
return err;
}
