mirror of
git://git.gnupg.org/gnupg.git
synced 2024-11-10 21:38:50 +01:00
29e6411a7b
rijndael.c, rndunix.c, sha256.c, cast5.c, idea-stub.c, rmd160.c, rndw32.c, sha512.c, md5.c, rmd160test.c, rsa.c, tiger.c: Edit all preprocessor instructions to remove whitespace before the '#'. This is not required by C89, but there are some compilers out there that don't like it.
665 lines
17 KiB
C
665 lines
17 KiB
C
/* elgamal.c - ElGamal Public Key encryption
|
|
* Copyright (C) 1998, 2000, 2001 Free Software Foundation, Inc.
|
|
*
|
|
* For a description of the algorithm, see:
|
|
* Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
|
|
* ISBN 0-471-11709-9. Pages 476 ff.
|
|
*
|
|
* This file is part of GnuPG.
|
|
*
|
|
* GnuPG is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* GnuPG 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 General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
|
|
*/
|
|
|
|
#include <config.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include "util.h"
|
|
#include "mpi.h"
|
|
#include "cipher.h"
|
|
#include "elgamal.h"
|
|
|
|
typedef struct {
|
|
MPI p; /* prime */
|
|
MPI g; /* group generator */
|
|
MPI y; /* g^x mod p */
|
|
} ELG_public_key;
|
|
|
|
|
|
typedef struct {
|
|
MPI p; /* prime */
|
|
MPI g; /* group generator */
|
|
MPI y; /* g^x mod p */
|
|
MPI x; /* secret exponent */
|
|
} ELG_secret_key;
|
|
|
|
|
|
static void test_keys( ELG_secret_key *sk, unsigned nbits );
|
|
static MPI gen_k( MPI p );
|
|
static void generate( ELG_secret_key *sk, unsigned nbits, MPI **factors );
|
|
static int check_secret_key( ELG_secret_key *sk );
|
|
static void do_encrypt(MPI a, MPI b, MPI input, ELG_public_key *pkey );
|
|
static void decrypt(MPI output, MPI a, MPI b, ELG_secret_key *skey );
|
|
static void sign(MPI a, MPI b, MPI input, ELG_secret_key *skey);
|
|
static int verify(MPI a, MPI b, MPI input, ELG_public_key *pkey);
|
|
|
|
|
|
static void (*progress_cb) ( void *, int );
|
|
static void *progress_cb_data;
|
|
|
|
void
|
|
register_pk_elg_progress ( void (*cb)( void *, 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, c );
|
|
else
|
|
fputc( c, stderr );
|
|
}
|
|
|
|
|
|
/****************
|
|
* Michael Wiener's table about subgroup sizes to match field sizes
|
|
* (floating around somewhere - Fixme: need a reference)
|
|
*/
|
|
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 some arbitrary high number ;-) */
|
|
return n / 8 + 200;
|
|
}
|
|
|
|
static void
|
|
test_keys( ELG_secret_key *sk, unsigned nbits )
|
|
{
|
|
ELG_public_key pk;
|
|
MPI test = mpi_alloc( 0 );
|
|
MPI out1_a = mpi_alloc( nbits / BITS_PER_MPI_LIMB );
|
|
MPI out1_b = mpi_alloc( nbits / BITS_PER_MPI_LIMB );
|
|
MPI out2 = mpi_alloc( nbits / BITS_PER_MPI_LIMB );
|
|
|
|
pk.p = sk->p;
|
|
pk.g = sk->g;
|
|
pk.y = sk->y;
|
|
|
|
/*mpi_set_bytes( test, nbits, get_random_byte, 0 );*/
|
|
{ char *p = get_random_bits( nbits, 0, 0 );
|
|
mpi_set_buffer( test, p, (nbits+7)/8, 0 );
|
|
m_free(p);
|
|
}
|
|
|
|
do_encrypt( out1_a, out1_b, test, &pk );
|
|
decrypt( out2, out1_a, out1_b, sk );
|
|
if( mpi_cmp( test, out2 ) )
|
|
log_fatal("ElGamal operation: encrypt, decrypt failed\n");
|
|
|
|
sign( out1_a, out1_b, test, sk );
|
|
if( !verify( out1_a, out1_b, test, &pk ) )
|
|
log_fatal("ElGamal operation: sign, verify failed\n");
|
|
|
|
mpi_free( test );
|
|
mpi_free( out1_a );
|
|
mpi_free( out1_b );
|
|
mpi_free( out2 );
|
|
}
|
|
|
|
|
|
/****************
|
|
* generate a random secret exponent k from prime p, so
|
|
* that k is relatively prime to p-1
|
|
*/
|
|
static MPI
|
|
gen_k( MPI p )
|
|
{
|
|
MPI k = mpi_alloc_secure( 0 );
|
|
MPI temp = mpi_alloc( mpi_get_nlimbs(p) );
|
|
MPI p_1 = mpi_copy(p);
|
|
unsigned int orig_nbits = mpi_get_nbits(p);
|
|
unsigned int nbits;
|
|
unsigned int nbytes;
|
|
char *rndbuf = NULL;
|
|
|
|
/* IMO using a k much lesser than p is sufficient 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();
|
|
|
|
nbytes = (nbits+7)/8;
|
|
if( DBG_CIPHER )
|
|
log_debug("choosing a random k of %u bits", nbits);
|
|
mpi_sub_ui( p_1, p, 1);
|
|
for(;;) {
|
|
if( !rndbuf || nbits < 32 ) {
|
|
m_free(rndbuf);
|
|
rndbuf = get_random_bits( nbits, 1, 1 );
|
|
}
|
|
else { /* change only some of the higher bits */
|
|
/* we could impprove this by directly requesting more memory
|
|
* at the first call to get_random_bits() 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 = get_random_bits( 32, 1, 1 );
|
|
memcpy( rndbuf,pp, 4 );
|
|
m_free(pp);
|
|
log_debug("gen_k: tsss, never expected to reach this\n");
|
|
}
|
|
mpi_set_buffer( k, rndbuf, nbytes, 0 );
|
|
|
|
for(;;) {
|
|
/* Hmm, actually we don't need this step here
|
|
* because we use k much smaller than p - we do it anyway
|
|
* just in case the keep on adding a one to k ;) */
|
|
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( mpi_gcd( temp, k, p_1 ) )
|
|
goto found; /* okay, k is relatively prime to (p-1) */
|
|
mpi_add_ui( k, k, 1 );
|
|
if( DBG_CIPHER )
|
|
progress('.');
|
|
}
|
|
}
|
|
found:
|
|
m_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 filles with all needed values
|
|
* and an array with n-1 factors of (p-1)
|
|
*/
|
|
static void
|
|
generate( ELG_secret_key *sk, unsigned int nbits, MPI **ret_factors )
|
|
{
|
|
MPI p; /* the prime */
|
|
MPI p_min1;
|
|
MPI g;
|
|
MPI x; /* the secret exponent */
|
|
MPI y;
|
|
MPI temp;
|
|
unsigned int qbits;
|
|
unsigned int xbits;
|
|
byte *rndbuf;
|
|
|
|
p_min1 = mpi_alloc( (nbits+BITS_PER_MPI_LIMB-1)/BITS_PER_MPI_LIMB );
|
|
temp = mpi_alloc( (nbits+BITS_PER_MPI_LIMB-1)/BITS_PER_MPI_LIMB );
|
|
qbits = wiener_map( nbits );
|
|
if( qbits & 1 ) /* better have a even one */
|
|
qbits++;
|
|
g = mpi_alloc(1);
|
|
p = 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 = mpi_alloc_secure( xbits/BITS_PER_MPI_LIMB );
|
|
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 ... */
|
|
m_free(rndbuf);
|
|
rndbuf = get_random_bits( xbits, 2, 1 );
|
|
}
|
|
else {
|
|
char *r = get_random_bits( 16, 2, 1 );
|
|
memcpy(rndbuf, r, 16/8 );
|
|
m_free(r);
|
|
}
|
|
}
|
|
else
|
|
rndbuf = get_random_bits( xbits, 2, 1 );
|
|
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 ) );
|
|
m_free(rndbuf);
|
|
|
|
y = mpi_alloc(nbits/BITS_PER_MPI_LIMB);
|
|
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;
|
|
|
|
/* now we can test our keys (this should never fail!) */
|
|
test_keys( sk, nbits - 64 );
|
|
|
|
mpi_free( p_min1 );
|
|
mpi_free( temp );
|
|
}
|
|
|
|
|
|
/****************
|
|
* 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;
|
|
MPI y = mpi_alloc( mpi_get_nlimbs(sk->y) );
|
|
|
|
mpi_powm( y, sk->g, sk->x, sk->p );
|
|
rc = !mpi_cmp( y, sk->y );
|
|
mpi_free( y );
|
|
return rc;
|
|
}
|
|
|
|
|
|
static void
|
|
do_encrypt(MPI a, MPI b, MPI input, ELG_public_key *pkey )
|
|
{
|
|
MPI 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 );
|
|
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
|
|
*/
|
|
mpi_powm( b, pkey->y, k, pkey->p );
|
|
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(MPI output, MPI a, MPI b, ELG_secret_key *skey )
|
|
{
|
|
MPI t1 = mpi_alloc_secure( mpi_get_nlimbs( skey->p ) );
|
|
|
|
/* output = b/(a^x) mod p */
|
|
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(MPI a, MPI b, MPI input, ELG_secret_key *skey )
|
|
{
|
|
MPI k;
|
|
MPI t = mpi_alloc( mpi_get_nlimbs(a) );
|
|
MPI inv = mpi_alloc( mpi_get_nlimbs(a) );
|
|
MPI 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 );
|
|
mpi_powm( a, skey->g, k, skey->p );
|
|
mpi_mul(t, skey->x, a );
|
|
mpi_subm(t, input, t, p_1 );
|
|
while( mpi_is_neg(t) ) {
|
|
BUG(); /* That is nonsense code - left over from a very early test?*/
|
|
mpi_add(t, 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(MPI a, MPI b, MPI input, ELG_public_key *pkey )
|
|
{
|
|
int rc;
|
|
MPI t1;
|
|
MPI t2;
|
|
MPI base[4];
|
|
MPI exp[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 */
|
|
mpi_powm( t1, pkey->y, a, pkey->p );
|
|
mpi_powm( t2, a, b, pkey->p );
|
|
mpi_mulm( t1, t1, t2, pkey->p );
|
|
|
|
/* t2 = g ^ input mod p */
|
|
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; exp[0] = a;
|
|
base[1] = a; exp[1] = b;
|
|
base[2] = NULL; exp[2] = NULL;
|
|
mpi_mulpowm( t1, base, exp, pkey->p );
|
|
|
|
/* t2 = g ^ input mod p */
|
|
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 ; exp[0] = input;
|
|
base[1] = pkey->y; exp[1] = a;
|
|
base[2] = a; exp[2] = b;
|
|
base[3] = NULL; exp[3] = NULL;
|
|
mpi_mulpowm( t1, base, exp, pkey->p );
|
|
rc = !mpi_cmp_ui( t1, 1 );
|
|
|
|
#endif
|
|
|
|
mpi_free(t1);
|
|
mpi_free(t2);
|
|
return rc;
|
|
}
|
|
|
|
/*********************************************
|
|
************** interface ******************
|
|
*********************************************/
|
|
|
|
int
|
|
elg_generate( int algo, unsigned nbits, MPI *skey, MPI **retfactors )
|
|
{
|
|
ELG_secret_key sk;
|
|
|
|
if( !is_ELGAMAL(algo) )
|
|
return G10ERR_PUBKEY_ALGO;
|
|
|
|
generate( &sk, nbits, retfactors );
|
|
skey[0] = sk.p;
|
|
skey[1] = sk.g;
|
|
skey[2] = sk.y;
|
|
skey[3] = sk.x;
|
|
return 0;
|
|
}
|
|
|
|
|
|
int
|
|
elg_check_secret_key( int algo, MPI *skey )
|
|
{
|
|
ELG_secret_key sk;
|
|
|
|
if( !is_ELGAMAL(algo) )
|
|
return G10ERR_PUBKEY_ALGO;
|
|
if( !skey[0] || !skey[1] || !skey[2] || !skey[3] )
|
|
return G10ERR_BAD_MPI;
|
|
|
|
sk.p = skey[0];
|
|
sk.g = skey[1];
|
|
sk.y = skey[2];
|
|
sk.x = skey[3];
|
|
if( !check_secret_key( &sk ) )
|
|
return G10ERR_BAD_SECKEY;
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
|
|
int
|
|
elg_encrypt( int algo, MPI *resarr, MPI data, MPI *pkey )
|
|
{
|
|
ELG_public_key pk;
|
|
|
|
if( !is_ELGAMAL(algo) )
|
|
return G10ERR_PUBKEY_ALGO;
|
|
if( !data || !pkey[0] || !pkey[1] || !pkey[2] )
|
|
return G10ERR_BAD_MPI;
|
|
|
|
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 0;
|
|
}
|
|
|
|
int
|
|
elg_decrypt( int algo, MPI *result, MPI *data, MPI *skey )
|
|
{
|
|
ELG_secret_key sk;
|
|
|
|
if( !is_ELGAMAL(algo) )
|
|
return G10ERR_PUBKEY_ALGO;
|
|
if( !data[0] || !data[1]
|
|
|| !skey[0] || !skey[1] || !skey[2] || !skey[3] )
|
|
return G10ERR_BAD_MPI;
|
|
|
|
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 0;
|
|
}
|
|
|
|
int
|
|
elg_sign( int algo, MPI *resarr, MPI data, MPI *skey )
|
|
{
|
|
ELG_secret_key sk;
|
|
|
|
if( !is_ELGAMAL(algo) )
|
|
return G10ERR_PUBKEY_ALGO;
|
|
if( !data || !skey[0] || !skey[1] || !skey[2] || !skey[3] )
|
|
return G10ERR_BAD_MPI;
|
|
|
|
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 0;
|
|
}
|
|
|
|
int
|
|
elg_verify( int algo, MPI hash, MPI *data, MPI *pkey,
|
|
int (*cmp)(void *, MPI), void *opaquev )
|
|
{
|
|
ELG_public_key pk;
|
|
|
|
if( !is_ELGAMAL(algo) )
|
|
return G10ERR_PUBKEY_ALGO;
|
|
if( !data[0] || !data[1] || !hash
|
|
|| !pkey[0] || !pkey[1] || !pkey[2] )
|
|
return G10ERR_BAD_MPI;
|
|
|
|
pk.p = pkey[0];
|
|
pk.g = pkey[1];
|
|
pk.y = pkey[2];
|
|
if( !verify( data[0], data[1], hash, &pk ) )
|
|
return G10ERR_BAD_SIGN;
|
|
return 0;
|
|
}
|
|
|
|
|
|
|
|
unsigned int
|
|
elg_get_nbits( int algo, MPI *pkey )
|
|
{
|
|
if( !is_ELGAMAL(algo) )
|
|
return 0;
|
|
return mpi_get_nbits( pkey[0] );
|
|
}
|
|
|
|
|
|
/****************
|
|
* Return some information about the algorithm. We need algo here to
|
|
* distinguish different flavors of the algorithm.
|
|
* Returns: A pointer to string describing the algorithm or NULL if
|
|
* the ALGO is invalid.
|
|
* Usage: Bit 0 set : allows signing
|
|
* 1 set : allows encryption
|
|
* NOTE: This function allows signing also for ELG-E, which is not
|
|
* okay but a bad hack to allow to work with old gpg keys. The real check
|
|
* is done in the gnupg ocde depending on the packet version.
|
|
*/
|
|
const char *
|
|
elg_get_info( int algo, int *npkey, int *nskey, int *nenc, int *nsig,
|
|
int *use )
|
|
{
|
|
*npkey = 3;
|
|
*nskey = 4;
|
|
*nenc = 2;
|
|
*nsig = 2;
|
|
|
|
switch( algo ) {
|
|
case PUBKEY_ALGO_ELGAMAL:
|
|
*use = PUBKEY_USAGE_SIG|PUBKEY_USAGE_ENC;
|
|
return "ELG";
|
|
case PUBKEY_ALGO_ELGAMAL_E:
|
|
*use = PUBKEY_USAGE_SIG|PUBKEY_USAGE_ENC;
|
|
return "ELG-E";
|
|
default: *use = 0; return NULL;
|
|
}
|
|
}
|