/* Elgamal.c - Elgamal Public Key encryption
* Copyright (C) 1998, 2000, 2001, 2002, 2003,
* 2008 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Libgcrypt is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* Libgcrypt is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, see .
*
* For a description of the algorithm, see:
* Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
* ISBN 0-471-11709-9. Pages 476 ff.
*/
#include
#include
#include
#include
#include "g10lib.h"
#include "mpi.h"
#include "cipher.h"
typedef struct
{
gcry_mpi_t p; /* prime */
gcry_mpi_t g; /* group generator */
gcry_mpi_t y; /* g^x mod p */
} ELG_public_key;
typedef struct
{
gcry_mpi_t p; /* prime */
gcry_mpi_t g; /* group generator */
gcry_mpi_t y; /* g^x mod p */
gcry_mpi_t x; /* secret exponent */
} ELG_secret_key;
static int test_keys (ELG_secret_key *sk, unsigned int nbits, int nodie);
static gcry_mpi_t gen_k (gcry_mpi_t p, int small_k);
static void generate (ELG_secret_key *sk, unsigned nbits, gcry_mpi_t **factors);
static int check_secret_key (ELG_secret_key *sk);
static void do_encrypt (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
ELG_public_key *pkey);
static void decrypt (gcry_mpi_t output, gcry_mpi_t a, gcry_mpi_t b,
ELG_secret_key *skey);
static void sign (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
ELG_secret_key *skey);
static int verify (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
ELG_public_key *pkey);
static void (*progress_cb) (void *, const char *, int, int, int);
static void *progress_cb_data;
void
_gcry_register_pk_elg_progress (void (*cb) (void *, const char *,
int, int, int),
void *cb_data)
{
progress_cb = cb;
progress_cb_data = cb_data;
}
static void
progress (int c)
{
if (progress_cb)
progress_cb (progress_cb_data, "pk_elg", c, 0, 0);
}
/****************
* Michael Wiener's table on subgroup sizes to match field sizes.
* (floating around somewhere, probably based on the paper from
* Eurocrypt 96, page 332)
*/
static unsigned int
wiener_map( unsigned int n )
{
static struct { unsigned int p_n, q_n; } t[] =
{ /* p q attack cost */
{ 512, 119 }, /* 9 x 10^17 */
{ 768, 145 }, /* 6 x 10^21 */
{ 1024, 165 }, /* 7 x 10^24 */
{ 1280, 183 }, /* 3 x 10^27 */
{ 1536, 198 }, /* 7 x 10^29 */
{ 1792, 212 }, /* 9 x 10^31 */
{ 2048, 225 }, /* 8 x 10^33 */
{ 2304, 237 }, /* 5 x 10^35 */
{ 2560, 249 }, /* 3 x 10^37 */
{ 2816, 259 }, /* 1 x 10^39 */
{ 3072, 269 }, /* 3 x 10^40 */
{ 3328, 279 }, /* 8 x 10^41 */
{ 3584, 288 }, /* 2 x 10^43 */
{ 3840, 296 }, /* 4 x 10^44 */
{ 4096, 305 }, /* 7 x 10^45 */
{ 4352, 313 }, /* 1 x 10^47 */
{ 4608, 320 }, /* 2 x 10^48 */
{ 4864, 328 }, /* 2 x 10^49 */
{ 5120, 335 }, /* 3 x 10^50 */
{ 0, 0 }
};
int i;
for(i=0; t[i].p_n; i++ )
{
if( n <= t[i].p_n )
return t[i].q_n;
}
/* Not in table - use an arbitrary high number. */
return n / 8 + 200;
}
static int
test_keys ( ELG_secret_key *sk, unsigned int nbits, int nodie )
{
ELG_public_key pk;
gcry_mpi_t test = gcry_mpi_new ( 0 );
gcry_mpi_t out1_a = gcry_mpi_new ( nbits );
gcry_mpi_t out1_b = gcry_mpi_new ( nbits );
gcry_mpi_t out2 = gcry_mpi_new ( nbits );
int failed = 0;
pk.p = sk->p;
pk.g = sk->g;
pk.y = sk->y;
gcry_mpi_randomize ( test, nbits, GCRY_WEAK_RANDOM );
do_encrypt ( out1_a, out1_b, test, &pk );
decrypt ( out2, out1_a, out1_b, sk );
if ( mpi_cmp( test, out2 ) )
failed |= 1;
sign ( out1_a, out1_b, test, sk );
if ( !verify( out1_a, out1_b, test, &pk ) )
failed |= 2;
gcry_mpi_release ( test );
gcry_mpi_release ( out1_a );
gcry_mpi_release ( out1_b );
gcry_mpi_release ( out2 );
if (failed && !nodie)
log_fatal ("Elgamal test key for %s %s failed\n",
(failed & 1)? "encrypt+decrypt":"",
(failed & 2)? "sign+verify":"");
if (failed && DBG_CIPHER)
log_debug ("Elgamal test key for %s %s failed\n",
(failed & 1)? "encrypt+decrypt":"",
(failed & 2)? "sign+verify":"");
return failed;
}
/****************
* Generate a random secret exponent k from prime p, so that k is
* relatively prime to p-1. With SMALL_K set, k will be selected for
* better encryption performance - this must never be used signing!
*/
static gcry_mpi_t
gen_k( gcry_mpi_t p, int small_k )
{
gcry_mpi_t k = mpi_alloc_secure( 0 );
gcry_mpi_t temp = mpi_alloc( mpi_get_nlimbs(p) );
gcry_mpi_t p_1 = mpi_copy(p);
unsigned int orig_nbits = mpi_get_nbits(p);
unsigned int nbits, nbytes;
char *rndbuf = NULL;
if (small_k)
{
/* Using a k much lesser than p is sufficient for encryption and
* it greatly improves the encryption performance. We use
* Wiener's table and add a large safety margin. */
nbits = wiener_map( orig_nbits ) * 3 / 2;
if( nbits >= orig_nbits )
BUG();
}
else
nbits = orig_nbits;
nbytes = (nbits+7)/8;
if( DBG_CIPHER )
log_debug("choosing a random k ");
mpi_sub_ui( p_1, p, 1);
for(;;)
{
if( !rndbuf || nbits < 32 )
{
gcry_free(rndbuf);
rndbuf = gcry_random_bytes_secure( nbytes, GCRY_STRONG_RANDOM );
}
else
{
/* Change only some of the higher bits. We could improve
this by directly requesting more memory at the first call
to get_random_bytes() and use this the here maybe it is
easier to do this directly in random.c Anyway, it is
highly inlikely that we will ever reach this code. */
char *pp = gcry_random_bytes_secure( 4, GCRY_STRONG_RANDOM );
memcpy( rndbuf, pp, 4 );
gcry_free(pp);
}
_gcry_mpi_set_buffer( k, rndbuf, nbytes, 0 );
for(;;)
{
if( !(mpi_cmp( k, p_1 ) < 0) ) /* check: k < (p-1) */
{
if( DBG_CIPHER )
progress('+');
break; /* no */
}
if( !(mpi_cmp_ui( k, 0 ) > 0) ) /* check: k > 0 */
{
if( DBG_CIPHER )
progress('-');
break; /* no */
}
if (gcry_mpi_gcd( temp, k, p_1 ))
goto found; /* okay, k is relative prime to (p-1) */
mpi_add_ui( k, k, 1 );
if( DBG_CIPHER )
progress('.');
}
}
found:
gcry_free(rndbuf);
if( DBG_CIPHER )
progress('\n');
mpi_free(p_1);
mpi_free(temp);
return k;
}
/****************
* Generate a key pair with a key of size NBITS
* Returns: 2 structures filled with all needed values
* and an array with n-1 factors of (p-1)
*/
static void
generate ( ELG_secret_key *sk, unsigned int nbits, gcry_mpi_t **ret_factors )
{
gcry_mpi_t p; /* the prime */
gcry_mpi_t p_min1;
gcry_mpi_t g;
gcry_mpi_t x; /* the secret exponent */
gcry_mpi_t y;
unsigned int qbits;
unsigned int xbits;
byte *rndbuf;
p_min1 = gcry_mpi_new ( nbits );
qbits = wiener_map( nbits );
if( qbits & 1 ) /* better have a even one */
qbits++;
g = mpi_alloc(1);
p = _gcry_generate_elg_prime( 0, nbits, qbits, g, ret_factors );
mpi_sub_ui(p_min1, p, 1);
/* Select a random number which has these properties:
* 0 < x < p-1
* This must be a very good random number because this is the
* secret part. The prime is public and may be shared anyway,
* so a random generator level of 1 is used for the prime.
*
* I don't see a reason to have a x of about the same size
* as the p. It should be sufficient to have one about the size
* of q or the later used k plus a large safety margin. Decryption
* will be much faster with such an x.
*/
xbits = qbits * 3 / 2;
if( xbits >= nbits )
BUG();
x = gcry_mpi_snew ( xbits );
if( DBG_CIPHER )
log_debug("choosing a random x of size %u", xbits );
rndbuf = NULL;
do
{
if( DBG_CIPHER )
progress('.');
if( rndbuf )
{ /* Change only some of the higher bits */
if( xbits < 16 ) /* should never happen ... */
{
gcry_free(rndbuf);
rndbuf = gcry_random_bytes_secure( (xbits+7)/8,
GCRY_VERY_STRONG_RANDOM );
}
else
{
char *r = gcry_random_bytes_secure( 2,
GCRY_VERY_STRONG_RANDOM );
memcpy(rndbuf, r, 2 );
gcry_free(r);
}
}
else
{
rndbuf = gcry_random_bytes_secure( (xbits+7)/8,
GCRY_VERY_STRONG_RANDOM );
}
_gcry_mpi_set_buffer( x, rndbuf, (xbits+7)/8, 0 );
mpi_clear_highbit( x, xbits+1 );
}
while( !( mpi_cmp_ui( x, 0 )>0 && mpi_cmp( x, p_min1 )<0 ) );
gcry_free(rndbuf);
y = gcry_mpi_new (nbits);
gcry_mpi_powm( y, g, x, p );
if( DBG_CIPHER )
{
progress('\n');
log_mpidump("elg p= ", p );
log_mpidump("elg g= ", g );
log_mpidump("elg y= ", y );
log_mpidump("elg x= ", x );
}
/* Copy the stuff to the key structures */
sk->p = p;
sk->g = g;
sk->y = y;
sk->x = x;
gcry_mpi_release ( p_min1 );
/* Now we can test our keys (this should never fail!) */
test_keys ( sk, nbits - 64, 0 );
}
/* Generate a key pair with a key of size NBITS not using a random
value for the secret key but the one given as X. This is useful to
implement a passphrase based decryption for a public key based
encryption. It has appliactions in backup systems.
Returns: A structure filled with all needed values and an array
with n-1 factors of (p-1). */
static gcry_err_code_t
generate_using_x (ELG_secret_key *sk, unsigned int nbits, gcry_mpi_t x,
gcry_mpi_t **ret_factors )
{
gcry_mpi_t p; /* The prime. */
gcry_mpi_t p_min1; /* The prime minus 1. */
gcry_mpi_t g; /* The generator. */
gcry_mpi_t y; /* g^x mod p. */
unsigned int qbits;
unsigned int xbits;
sk->p = NULL;
sk->g = NULL;
sk->y = NULL;
sk->x = NULL;
/* Do a quick check to see whether X is suitable. */
xbits = mpi_get_nbits (x);
if ( xbits < 64 || xbits >= nbits )
return GPG_ERR_INV_VALUE;
p_min1 = gcry_mpi_new ( nbits );
qbits = wiener_map ( nbits );
if ( (qbits & 1) ) /* Better have an even one. */
qbits++;
g = mpi_alloc (1);
p = _gcry_generate_elg_prime ( 0, nbits, qbits, g, ret_factors );
mpi_sub_ui (p_min1, p, 1);
if (DBG_CIPHER)
log_debug ("using a supplied x of size %u", xbits );
if ( !(mpi_cmp_ui ( x, 0 ) > 0 && mpi_cmp ( x, p_min1 ) <0 ) )
{
gcry_mpi_release ( p_min1 );
gcry_mpi_release ( p );
gcry_mpi_release ( g );
return GPG_ERR_INV_VALUE;
}
y = gcry_mpi_new (nbits);
gcry_mpi_powm ( y, g, x, p );
if ( DBG_CIPHER )
{
progress ('\n');
log_mpidump ("elg p= ", p );
log_mpidump ("elg g= ", g );
log_mpidump ("elg y= ", y );
log_mpidump ("elg x= ", x );
}
/* Copy the stuff to the key structures */
sk->p = p;
sk->g = g;
sk->y = y;
sk->x = gcry_mpi_copy (x);
gcry_mpi_release ( p_min1 );
/* Now we can test our keys. */
if ( test_keys ( sk, nbits - 64, 1 ) )
{
gcry_mpi_release ( sk->p ); sk->p = NULL;
gcry_mpi_release ( sk->g ); sk->g = NULL;
gcry_mpi_release ( sk->y ); sk->y = NULL;
gcry_mpi_release ( sk->x ); sk->x = NULL;
return GPG_ERR_BAD_SECKEY;
}
return 0;
}
/****************
* Test whether the secret key is valid.
* Returns: if this is a valid key.
*/
static int
check_secret_key( ELG_secret_key *sk )
{
int rc;
gcry_mpi_t y = mpi_alloc( mpi_get_nlimbs(sk->y) );
gcry_mpi_powm( y, sk->g, sk->x, sk->p );
rc = !mpi_cmp( y, sk->y );
mpi_free( y );
return rc;
}
static void
do_encrypt(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_public_key *pkey )
{
gcry_mpi_t k;
/* Note: maybe we should change the interface, so that it
* is possible to check that input is < p and return an
* error code.
*/
k = gen_k( pkey->p, 1 );
gcry_mpi_powm( a, pkey->g, k, pkey->p );
/* b = (y^k * input) mod p
* = ((y^k mod p) * (input mod p)) mod p
* and because input is < p
* = ((y^k mod p) * input) mod p
*/
gcry_mpi_powm( b, pkey->y, k, pkey->p );
gcry_mpi_mulm( b, b, input, pkey->p );
#if 0
if( DBG_CIPHER )
{
log_mpidump("elg encrypted y= ", pkey->y);
log_mpidump("elg encrypted p= ", pkey->p);
log_mpidump("elg encrypted k= ", k);
log_mpidump("elg encrypted M= ", input);
log_mpidump("elg encrypted a= ", a);
log_mpidump("elg encrypted b= ", b);
}
#endif
mpi_free(k);
}
static void
decrypt(gcry_mpi_t output, gcry_mpi_t a, gcry_mpi_t b, ELG_secret_key *skey )
{
gcry_mpi_t t1 = mpi_alloc_secure( mpi_get_nlimbs( skey->p ) );
/* output = b/(a^x) mod p */
gcry_mpi_powm( t1, a, skey->x, skey->p );
mpi_invm( t1, t1, skey->p );
mpi_mulm( output, b, t1, skey->p );
#if 0
if( DBG_CIPHER )
{
log_mpidump("elg decrypted x= ", skey->x);
log_mpidump("elg decrypted p= ", skey->p);
log_mpidump("elg decrypted a= ", a);
log_mpidump("elg decrypted b= ", b);
log_mpidump("elg decrypted M= ", output);
}
#endif
mpi_free(t1);
}
/****************
* Make an Elgamal signature out of INPUT
*/
static void
sign(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_secret_key *skey )
{
gcry_mpi_t k;
gcry_mpi_t t = mpi_alloc( mpi_get_nlimbs(a) );
gcry_mpi_t inv = mpi_alloc( mpi_get_nlimbs(a) );
gcry_mpi_t p_1 = mpi_copy(skey->p);
/*
* b = (t * inv) mod (p-1)
* b = (t * inv(k,(p-1),(p-1)) mod (p-1)
* b = (((M-x*a) mod (p-1)) * inv(k,(p-1),(p-1))) mod (p-1)
*
*/
mpi_sub_ui(p_1, p_1, 1);
k = gen_k( skey->p, 0 /* no small K ! */ );
gcry_mpi_powm( a, skey->g, k, skey->p );
mpi_mul(t, skey->x, a );
mpi_subm(t, input, t, p_1 );
mpi_invm(inv, k, p_1 );
mpi_mulm(b, t, inv, p_1 );
#if 0
if( DBG_CIPHER )
{
log_mpidump("elg sign p= ", skey->p);
log_mpidump("elg sign g= ", skey->g);
log_mpidump("elg sign y= ", skey->y);
log_mpidump("elg sign x= ", skey->x);
log_mpidump("elg sign k= ", k);
log_mpidump("elg sign M= ", input);
log_mpidump("elg sign a= ", a);
log_mpidump("elg sign b= ", b);
}
#endif
mpi_free(k);
mpi_free(t);
mpi_free(inv);
mpi_free(p_1);
}
/****************
* Returns true if the signature composed of A and B is valid.
*/
static int
verify(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_public_key *pkey )
{
int rc;
gcry_mpi_t t1;
gcry_mpi_t t2;
gcry_mpi_t base[4];
gcry_mpi_t ex[4];
if( !(mpi_cmp_ui( a, 0 ) > 0 && mpi_cmp( a, pkey->p ) < 0) )
return 0; /* assertion 0 < a < p failed */
t1 = mpi_alloc( mpi_get_nlimbs(a) );
t2 = mpi_alloc( mpi_get_nlimbs(a) );
#if 0
/* t1 = (y^a mod p) * (a^b mod p) mod p */
gcry_mpi_powm( t1, pkey->y, a, pkey->p );
gcry_mpi_powm( t2, a, b, pkey->p );
mpi_mulm( t1, t1, t2, pkey->p );
/* t2 = g ^ input mod p */
gcry_mpi_powm( t2, pkey->g, input, pkey->p );
rc = !mpi_cmp( t1, t2 );
#elif 0
/* t1 = (y^a mod p) * (a^b mod p) mod p */
base[0] = pkey->y; ex[0] = a;
base[1] = a; ex[1] = b;
base[2] = NULL; ex[2] = NULL;
mpi_mulpowm( t1, base, ex, pkey->p );
/* t2 = g ^ input mod p */
gcry_mpi_powm( t2, pkey->g, input, pkey->p );
rc = !mpi_cmp( t1, t2 );
#else
/* t1 = g ^ - input * y ^ a * a ^ b mod p */
mpi_invm(t2, pkey->g, pkey->p );
base[0] = t2 ; ex[0] = input;
base[1] = pkey->y; ex[1] = a;
base[2] = a; ex[2] = b;
base[3] = NULL; ex[3] = NULL;
mpi_mulpowm( t1, base, ex, pkey->p );
rc = !mpi_cmp_ui( t1, 1 );
#endif
mpi_free(t1);
mpi_free(t2);
return rc;
}
/*********************************************
************** interface ******************
*********************************************/
static gpg_err_code_t
elg_generate_ext (int algo, unsigned int nbits, unsigned long evalue,
const gcry_sexp_t genparms,
gcry_mpi_t *skey, gcry_mpi_t **retfactors,
gcry_sexp_t *r_extrainfo)
{
gpg_err_code_t ec;
ELG_secret_key sk;
gcry_mpi_t xvalue = NULL;
gcry_sexp_t l1;
(void)algo;
(void)evalue;
(void)r_extrainfo;
if (genparms)
{
/* Parse the optional xvalue element. */
l1 = gcry_sexp_find_token (genparms, "xvalue", 0);
if (l1)
{
xvalue = gcry_sexp_nth_mpi (l1, 1, 0);
gcry_sexp_release (l1);
if (!xvalue)
return GPG_ERR_BAD_MPI;
}
}
if (xvalue)
ec = generate_using_x (&sk, nbits, xvalue, retfactors);
else
{
generate (&sk, nbits, retfactors);
ec = 0;
}
skey[0] = sk.p;
skey[1] = sk.g;
skey[2] = sk.y;
skey[3] = sk.x;
return ec;
}
static gcry_err_code_t
elg_generate (int algo, unsigned int nbits, unsigned long evalue,
gcry_mpi_t *skey, gcry_mpi_t **retfactors)
{
ELG_secret_key sk;
(void)algo;
(void)evalue;
generate (&sk, nbits, retfactors);
skey[0] = sk.p;
skey[1] = sk.g;
skey[2] = sk.y;
skey[3] = sk.x;
return GPG_ERR_NO_ERROR;
}
static gcry_err_code_t
elg_check_secret_key (int algo, gcry_mpi_t *skey)
{
gcry_err_code_t err = GPG_ERR_NO_ERROR;
ELG_secret_key sk;
(void)algo;
if ((! skey[0]) || (! skey[1]) || (! skey[2]) || (! skey[3]))
err = GPG_ERR_BAD_MPI;
else
{
sk.p = skey[0];
sk.g = skey[1];
sk.y = skey[2];
sk.x = skey[3];
if (! check_secret_key (&sk))
err = GPG_ERR_BAD_SECKEY;
}
return err;
}
static gcry_err_code_t
elg_encrypt (int algo, gcry_mpi_t *resarr,
gcry_mpi_t data, gcry_mpi_t *pkey, int flags)
{
gcry_err_code_t err = GPG_ERR_NO_ERROR;
ELG_public_key pk;
(void)algo;
(void)flags;
if ((! data) || (! pkey[0]) || (! pkey[1]) || (! pkey[2]))
err = GPG_ERR_BAD_MPI;
else
{
pk.p = pkey[0];
pk.g = pkey[1];
pk.y = pkey[2];
resarr[0] = mpi_alloc (mpi_get_nlimbs (pk.p));
resarr[1] = mpi_alloc (mpi_get_nlimbs (pk.p));
do_encrypt (resarr[0], resarr[1], data, &pk);
}
return err;
}
static gcry_err_code_t
elg_decrypt (int algo, gcry_mpi_t *result,
gcry_mpi_t *data, gcry_mpi_t *skey, int flags)
{
gcry_err_code_t err = GPG_ERR_NO_ERROR;
ELG_secret_key sk;
(void)algo;
(void)flags;
if ((! data[0]) || (! data[1])
|| (! skey[0]) || (! skey[1]) || (! skey[2]) || (! skey[3]))
err = GPG_ERR_BAD_MPI;
else
{
sk.p = skey[0];
sk.g = skey[1];
sk.y = skey[2];
sk.x = skey[3];
*result = mpi_alloc_secure (mpi_get_nlimbs (sk.p));
decrypt (*result, data[0], data[1], &sk);
}
return err;
}
static gcry_err_code_t
elg_sign (int algo, gcry_mpi_t *resarr, gcry_mpi_t data, gcry_mpi_t *skey)
{
gcry_err_code_t err = GPG_ERR_NO_ERROR;
ELG_secret_key sk;
(void)algo;
if ((! data)
|| (! skey[0]) || (! skey[1]) || (! skey[2]) || (! skey[3]))
err = GPG_ERR_BAD_MPI;
else
{
sk.p = skey[0];
sk.g = skey[1];
sk.y = skey[2];
sk.x = skey[3];
resarr[0] = mpi_alloc (mpi_get_nlimbs (sk.p));
resarr[1] = mpi_alloc (mpi_get_nlimbs (sk.p));
sign (resarr[0], resarr[1], data, &sk);
}
return err;
}
static gcry_err_code_t
elg_verify (int algo, gcry_mpi_t hash, gcry_mpi_t *data, gcry_mpi_t *pkey,
int (*cmp) (void *, gcry_mpi_t), void *opaquev)
{
gcry_err_code_t err = GPG_ERR_NO_ERROR;
ELG_public_key pk;
(void)algo;
(void)cmp;
(void)opaquev;
if ((! data[0]) || (! data[1]) || (! hash)
|| (! pkey[0]) || (! pkey[1]) || (! pkey[2]))
err = GPG_ERR_BAD_MPI;
else
{
pk.p = pkey[0];
pk.g = pkey[1];
pk.y = pkey[2];
if (! verify (data[0], data[1], hash, &pk))
err = GPG_ERR_BAD_SIGNATURE;
}
return err;
}
static unsigned int
elg_get_nbits (int algo, gcry_mpi_t *pkey)
{
(void)algo;
return mpi_get_nbits (pkey[0]);
}
static const char *elg_names[] =
{
"elg",
"openpgp-elg",
"openpgp-elg-sig",
NULL,
};
gcry_pk_spec_t _gcry_pubkey_spec_elg =
{
"ELG", elg_names,
"pgy", "pgyx", "ab", "rs", "pgy",
GCRY_PK_USAGE_SIGN | GCRY_PK_USAGE_ENCR,
elg_generate,
elg_check_secret_key,
elg_encrypt,
elg_decrypt,
elg_sign,
elg_verify,
elg_get_nbits
};
pk_extra_spec_t _gcry_pubkey_extraspec_elg =
{
NULL,
elg_generate_ext,
NULL
};