bool
rsa_test(unsigned bits, mt64_context *rand_ctx)
{
mt64_init_u64(rand_ctx, 1234567890U);
rsa_ctx rsa;
if (!rsa_init_keygen(&rsa, bits, rand_ctx))
return false;
ASSERT(rsa.n != NULL);
ASSERT(rsa.phi != NULL);
ASSERT(rsa.e != NULL);
ASSERT(rsa.d != NULL);
mpi_t m = MPI_INITIALIZER;
mpi_mul(rsa.e, rsa.d, m);
mpi_mod(m, rsa.phi, m);
bool result = true;
if (!mpi_is_one(m)) {
printf("N: "), mpi_print_dec(rsa.n), printf("\n");
printf("E: "), mpi_print_dec(rsa.e), printf("\n");
printf("D: "), mpi_print_dec(rsa.d), printf("\n");
printf("Φ: "), mpi_print_dec(rsa.phi), printf("\n");
printf("E * D mod Φ: "), mpi_print_dec(m), printf("\n");
result = false;
}
mpi_free(m);
rsa_free(&rsa);
return result;
}
/* R = X mod M
Using Barrett reduction. Before using this function
_gcry_mpi_barrett_init must have been called to do the
precalculations. CTX is the context created by this precalculation
and also conveys M. If the Barret reduction could no be done a
straightforward reduction method is used.
We assume that these conditions are met:
Input: x =(x_2k-1 ...x_0)_b
m =(m_k-1 ....m_0)_b with m_k-1 != 0
Output: r = x mod m
*/
void
_gcry_mpi_mod_barrett (gcry_mpi_t r, gcry_mpi_t x, mpi_barrett_t ctx)
{
gcry_mpi_t m = ctx->m;
int k = ctx->k;
gcry_mpi_t y = ctx->y;
gcry_mpi_t r1 = ctx->r1;
gcry_mpi_t r2 = ctx->r2;
int sign;
mpi_normalize (x);
if (mpi_get_nlimbs (x) > 2*k )
{
mpi_mod (r, x, m);
return;
}
sign = x->sign;
x->sign = 0;
/* 1. q1 = floor( x / b^k-1)
* q2 = q1 * y
* q3 = floor( q2 / b^k+1 )
* Actually, we don't need qx, we can work direct on r2
*/
mpi_set ( r2, x );
mpi_rshift_limbs ( r2, k-1 );
mpi_mul ( r2, r2, y );
mpi_rshift_limbs ( r2, k+1 );
/* 2. r1 = x mod b^k+1
* r2 = q3 * m mod b^k+1
* r = r1 - r2
* 3. if r < 0 then r = r + b^k+1
*/
mpi_set ( r1, x );
if ( r1->nlimbs > k+1 ) /* Quick modulo operation. */
r1->nlimbs = k+1;
mpi_mul ( r2, r2, m );
if ( r2->nlimbs > k+1 ) /* Quick modulo operation. */
r2->nlimbs = k+1;
mpi_sub ( r, r1, r2 );
if ( mpi_has_sign ( r ) )
{
if (!ctx->r3)
{
ctx->r3 = mpi_alloc ( k + 2 );
mpi_set_ui (ctx->r3, 1);
mpi_lshift_limbs (ctx->r3, k + 1 );
}
mpi_add ( r, r, ctx->r3 );
}
/* 4. while r >= m do r = r - m */
while ( mpi_cmp( r, m ) >= 0 )
mpi_sub ( r, r, m );
x->sign = sign;
}
/*
* Return the signature struct (r,s) from the message hash. The caller
* must have allocated R and S.
*/
static gpg_err_code_t
sign (gcry_mpi_t input, ECC_secret_key *skey, gcry_mpi_t r, gcry_mpi_t s)
{
gpg_err_code_t err = 0;
gcry_mpi_t k, dr, sum, k_1, x;
mpi_point_t I;
mpi_ec_t ctx;
k = NULL;
dr = mpi_alloc (0);
sum = mpi_alloc (0);
k_1 = mpi_alloc (0);
x = mpi_alloc (0);
point_init (&I);
mpi_set_ui (s, 0);
mpi_set_ui (r, 0);
ctx = _gcry_mpi_ec_init (skey->E.p, skey->E.a);
while (!mpi_cmp_ui (s, 0)) /* s == 0 */
{
while (!mpi_cmp_ui (r, 0)) /* r == 0 */
{
/* Note, that we are guaranteed to enter this loop at least
once because r has been intialized to 0. We can't use a
do_while because we want to keep the value of R even if S
has to be recomputed. */
mpi_free (k);
k = gen_k (skey->E.n, GCRY_STRONG_RANDOM);
_gcry_mpi_ec_mul_point (&I, k, &skey->E.G, ctx);
if (_gcry_mpi_ec_get_affine (x, NULL, &I, ctx))
{
if (DBG_CIPHER)
log_debug ("ecc sign: Failed to get affine coordinates\n");
err = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
mpi_mod (r, x, skey->E.n); /* r = x mod n */
}
mpi_mulm (dr, skey->d, r, skey->E.n); /* dr = d*r mod n */
mpi_addm (sum, input, dr, skey->E.n); /* sum = hash + (d*r) mod n */
mpi_invm (k_1, k, skey->E.n); /* k_1 = k^(-1) mod n */
mpi_mulm (s, k_1, sum, skey->E.n); /* s = k^(-1)*(hash+(d*r)) mod n */
}
leave:
_gcry_mpi_ec_free (ctx);
point_free (&I);
mpi_free (x);
mpi_free (k_1);
mpi_free (sum);
mpi_free (dr);
mpi_free (k);
return err;
}
static void
do_rem (void)
{
if (stackidx < 2)
{
fputs ("stack underflow\n", stderr);
return;
}
mpi_mod (stack[stackidx - 2],
stack[stackidx - 2], stack[stackidx - 1]);
stackidx--;
}
/* Generate a random secret scalar k with an order of p
At the beginning this was identical to the code is in elgamal.c.
Later imporved by mmr. Further simplified by wk. */
static gcry_mpi_t
gen_k (gcry_mpi_t p, int security_level)
{
gcry_mpi_t k;
unsigned int nbits;
nbits = mpi_get_nbits (p);
k = mpi_snew (nbits);
if (DBG_CIPHER)
log_debug ("choosing a random k of %u bits\n", nbits);
gcry_mpi_randomize (k, nbits, security_level);
mpi_mod (k, k, p); /* k = k mod p */
return k;
}
int
mpi_crt_step(mpi_crt_ctx *ctx, const mpi *a_i, const mpi *m_i)
{
if (ctx->i == 0) {
mpi_init_mpi(ctx->x, a_i);
mpi_init_mpi(ctx->m, m_i);
} else {
mpi_t u, v, gcd;
mpi_init(u);
mpi_init(v);
mpi_init(gcd);
mpi_gcdext(ctx->m, m_i, u, v, gcd);
if (!mpi_is_one(gcd)) {
mpi_free(u);
mpi_free(v);
mpi_free(gcd);
mpi_free(ctx->x);
mpi_free(ctx->m);
ctx->i = 0;
return -1;
}
mpi_mul(u, ctx->m, u);
mpi_mul(u, a_i, u);
mpi_mul(v, m_i, v);
mpi_mul(v, ctx->x, v);
mpi_add(u, v, ctx->x);
mpi_mul(ctx->m, m_i, ctx->m);
mpi_mod(ctx->x, ctx->m, ctx->x);
mpi_free(u);
mpi_free(v);
mpi_free(gcd);
}
ctx->i++;
return 0;
}
/*
* Check if R and S verifies INPUT.
*/
static gpg_err_code_t
verify (gcry_mpi_t input, ECC_public_key *pkey, gcry_mpi_t r, gcry_mpi_t s)
{
gpg_err_code_t err = 0;
gcry_mpi_t h, h1, h2, x, y;
mpi_point_t Q, Q1, Q2;
mpi_ec_t ctx;
if( !(mpi_cmp_ui (r, 0) > 0 && mpi_cmp (r, pkey->E.n) < 0) )
return GPG_ERR_BAD_SIGNATURE; /* Assertion 0 < r < n failed. */
if( !(mpi_cmp_ui (s, 0) > 0 && mpi_cmp (s, pkey->E.n) < 0) )
return GPG_ERR_BAD_SIGNATURE; /* Assertion 0 < s < n failed. */
h = mpi_alloc (0);
h1 = mpi_alloc (0);
h2 = mpi_alloc (0);
x = mpi_alloc (0);
y = mpi_alloc (0);
point_init (&Q);
point_init (&Q1);
point_init (&Q2);
ctx = _gcry_mpi_ec_init (pkey->E.p, pkey->E.a);
/* h = s^(-1) (mod n) */
mpi_invm (h, s, pkey->E.n);
/* log_mpidump (" h", h); */
/* h1 = hash * s^(-1) (mod n) */
mpi_mulm (h1, input, h, pkey->E.n);
/* log_mpidump (" h1", h1); */
/* Q1 = [ hash * s^(-1) ]G */
_gcry_mpi_ec_mul_point (&Q1, h1, &pkey->E.G, ctx);
/* log_mpidump ("Q1.x", Q1.x); */
/* log_mpidump ("Q1.y", Q1.y); */
/* log_mpidump ("Q1.z", Q1.z); */
/* h2 = r * s^(-1) (mod n) */
mpi_mulm (h2, r, h, pkey->E.n);
/* log_mpidump (" h2", h2); */
/* Q2 = [ r * s^(-1) ]Q */
_gcry_mpi_ec_mul_point (&Q2, h2, &pkey->Q, ctx);
/* log_mpidump ("Q2.x", Q2.x); */
/* log_mpidump ("Q2.y", Q2.y); */
/* log_mpidump ("Q2.z", Q2.z); */
/* Q = ([hash * s^(-1)]G) + ([r * s^(-1)]Q) */
_gcry_mpi_ec_add_points (&Q, &Q1, &Q2, ctx);
/* log_mpidump (" Q.x", Q.x); */
/* log_mpidump (" Q.y", Q.y); */
/* log_mpidump (" Q.z", Q.z); */
if (!mpi_cmp_ui (Q.z, 0))
{
if (DBG_CIPHER)
log_debug ("ecc verify: Rejected\n");
err = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
if (_gcry_mpi_ec_get_affine (x, y, &Q, ctx))
{
if (DBG_CIPHER)
log_debug ("ecc verify: Failed to get affine coordinates\n");
err = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
mpi_mod (x, x, pkey->E.n); /* x = x mod E_n */
if (mpi_cmp (x, r)) /* x != r */
{
if (DBG_CIPHER)
{
log_mpidump (" x", x);
log_mpidump (" y", y);
log_mpidump (" r", r);
log_mpidump (" s", s);
log_debug ("ecc verify: Not verified\n");
}
err = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
if (DBG_CIPHER)
log_debug ("ecc verify: Accepted\n");
leave:
_gcry_mpi_ec_free (ctx);
point_free (&Q2);
point_free (&Q1);
point_free (&Q);
mpi_free (y);
mpi_free (x);
mpi_free (h2);
mpi_free (h1);
mpi_free (h);
return err;
}
/* Compute an ECDSA signature.
* Return the signature struct (r,s) from the message hash. The caller
* must have allocated R and S.
*/
gpg_err_code_t
_gcry_ecc_ecdsa_sign (gcry_mpi_t input, ECC_secret_key *skey,
gcry_mpi_t r, gcry_mpi_t s,
int flags, int hashalgo)
{
gpg_err_code_t err = 0;
int extraloops = 0;
gcry_mpi_t k, dr, sum, k_1, x;
mpi_point_struct I;
gcry_mpi_t hash;
const void *abuf;
unsigned int abits, qbits;
mpi_ec_t ctx;
if (DBG_CIPHER)
log_mpidump ("ecdsa sign hash ", input );
qbits = mpi_get_nbits (skey->E.n);
/* Convert the INPUT into an MPI if needed. */
if (mpi_is_opaque (input))
{
abuf = gcry_mpi_get_opaque (input, &abits);
err = gpg_err_code (gcry_mpi_scan (&hash, GCRYMPI_FMT_USG,
abuf, (abits+7)/8, NULL));
if (err)
return err;
if (abits > qbits)
gcry_mpi_rshift (hash, hash, abits - qbits);
}
else
hash = input;
k = NULL;
dr = mpi_alloc (0);
sum = mpi_alloc (0);
k_1 = mpi_alloc (0);
x = mpi_alloc (0);
point_init (&I);
ctx = _gcry_mpi_ec_p_internal_new (skey->E.model, skey->E.dialect,
skey->E.p, skey->E.a, skey->E.b);
/* Two loops to avoid R or S are zero. This is more of a joke than
a real demand because the probability of them being zero is less
than any hardware failure. Some specs however require it. */
do
{
do
{
mpi_free (k);
k = NULL;
if ((flags & PUBKEY_FLAG_RFC6979) && hashalgo)
{
/* Use Pornin's method for deterministic DSA. If this
flag is set, it is expected that HASH is an opaque
MPI with the to be signed hash. That hash is also
used as h1 from 3.2.a. */
if (!mpi_is_opaque (input))
{
err = GPG_ERR_CONFLICT;
goto leave;
}
abuf = gcry_mpi_get_opaque (input, &abits);
err = _gcry_dsa_gen_rfc6979_k (&k, skey->E.n, skey->d,
abuf, (abits+7)/8,
hashalgo, extraloops);
if (err)
goto leave;
extraloops++;
}
else
k = _gcry_dsa_gen_k (skey->E.n, GCRY_STRONG_RANDOM);
_gcry_mpi_ec_mul_point (&I, k, &skey->E.G, ctx);
if (_gcry_mpi_ec_get_affine (x, NULL, &I, ctx))
{
if (DBG_CIPHER)
log_debug ("ecc sign: Failed to get affine coordinates\n");
err = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
mpi_mod (r, x, skey->E.n); /* r = x mod n */
}
while (!mpi_cmp_ui (r, 0));
mpi_mulm (dr, skey->d, r, skey->E.n); /* dr = d*r mod n */
mpi_addm (sum, hash, dr, skey->E.n); /* sum = hash + (d*r) mod n */
mpi_invm (k_1, k, skey->E.n); /* k_1 = k^(-1) mod n */
mpi_mulm (s, k_1, sum, skey->E.n); /* s = k^(-1)*(hash+(d*r)) mod n */
}
while (!mpi_cmp_ui (s, 0));
if (DBG_CIPHER)
{
log_mpidump ("ecdsa sign result r ", r);
log_mpidump ("ecdsa sign result s ", s);
}
leave:
_gcry_mpi_ec_free (ctx);
point_free (&I);
mpi_free (x);
mpi_free (k_1);
mpi_free (sum);
mpi_free (dr);
mpi_free (k);
if (hash != input)
mpi_free (hash);
return err;
}
/* Verify an ECDSA signature.
* Check if R and S verifies INPUT.
*/
gpg_err_code_t
_gcry_ecc_ecdsa_verify (gcry_mpi_t input, ECC_public_key *pkey,
gcry_mpi_t r, gcry_mpi_t s)
{
gpg_err_code_t err = 0;
gcry_mpi_t h, h1, h2, x;
mpi_point_struct Q, Q1, Q2;
mpi_ec_t ctx;
if( !(mpi_cmp_ui (r, 0) > 0 && mpi_cmp (r, pkey->E.n) < 0) )
return GPG_ERR_BAD_SIGNATURE; /* Assertion 0 < r < n failed. */
if( !(mpi_cmp_ui (s, 0) > 0 && mpi_cmp (s, pkey->E.n) < 0) )
return GPG_ERR_BAD_SIGNATURE; /* Assertion 0 < s < n failed. */
h = mpi_alloc (0);
h1 = mpi_alloc (0);
h2 = mpi_alloc (0);
x = mpi_alloc (0);
point_init (&Q);
point_init (&Q1);
point_init (&Q2);
ctx = _gcry_mpi_ec_p_internal_new (pkey->E.model, pkey->E.dialect,
pkey->E.p, pkey->E.a, pkey->E.b);
/* h = s^(-1) (mod n) */
mpi_invm (h, s, pkey->E.n);
/* h1 = hash * s^(-1) (mod n) */
mpi_mulm (h1, input, h, pkey->E.n);
/* Q1 = [ hash * s^(-1) ]G */
_gcry_mpi_ec_mul_point (&Q1, h1, &pkey->E.G, ctx);
/* h2 = r * s^(-1) (mod n) */
mpi_mulm (h2, r, h, pkey->E.n);
/* Q2 = [ r * s^(-1) ]Q */
_gcry_mpi_ec_mul_point (&Q2, h2, &pkey->Q, ctx);
/* Q = ([hash * s^(-1)]G) + ([r * s^(-1)]Q) */
_gcry_mpi_ec_add_points (&Q, &Q1, &Q2, ctx);
if (!mpi_cmp_ui (Q.z, 0))
{
if (DBG_CIPHER)
log_debug ("ecc verify: Rejected\n");
err = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
if (_gcry_mpi_ec_get_affine (x, NULL, &Q, ctx))
{
if (DBG_CIPHER)
log_debug ("ecc verify: Failed to get affine coordinates\n");
err = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
mpi_mod (x, x, pkey->E.n); /* x = x mod E_n */
if (mpi_cmp (x, r)) /* x != r */
{
if (DBG_CIPHER)
{
log_mpidump (" x", x);
log_mpidump (" r", r);
log_mpidump (" s", s);
}
err = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
leave:
_gcry_mpi_ec_free (ctx);
point_free (&Q2);
point_free (&Q1);
point_free (&Q);
mpi_free (x);
mpi_free (h2);
mpi_free (h1);
mpi_free (h);
return err;
}