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-rw-r--r--cipher/elgamal.c661
1 files changed, 0 insertions, 661 deletions
diff --git a/cipher/elgamal.c b/cipher/elgamal.c
deleted file mode 100644
index c2c2c6e1a..000000000
--- a/cipher/elgamal.c
+++ /dev/null
@@ -1,661 +0,0 @@
-/* elgamal.c - ElGamal Public Key encryption
- * Copyright (C) 1998, 2000 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 "g10lib.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 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 on 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 = gcry_mpi_new ( 0 );
- MPI out1_a = gcry_mpi_new ( nbits );
- MPI out1_b = gcry_mpi_new ( nbits );
- MPI out2 = gcry_mpi_new ( nbits );
-
- pk.p = sk->p;
- pk.g = sk->g;
- pk.y = sk->y;
-
- gcry_mpi_randomize( test, nbits, GCRY_WEAK_RANDOM );
-
- 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");
-
- gcry_mpi_release ( test );
- gcry_mpi_release ( out1_a );
- gcry_mpi_release ( out1_b );
- gcry_mpi_release ( 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, 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 ");
- mpi_sub_ui( p_1, p, 1);
- for(;;) {
- if( !rndbuf || nbits < 32 ) {
- g10_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 );
- g10_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:
- g10_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 = gcry_mpi_new ( nbits );
- temp = gcry_mpi_new( nbits );
- 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 = 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 ... */
- g10_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 );
- g10_free(r);
- }
- }
- else {
- rndbuf = gcry_random_bytes_secure( (xbits+7)/8,
- GCRY_VERY_STRONG_RANDOM );
- }
- 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 ) );
- g10_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;
-
- /* now we can test our keys (this should never fail!) */
- test_keys( sk, nbits - 64 );
-
- gcry_mpi_release ( p_min1 );
- gcry_mpi_release ( 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) );
-
- gcry_mpi_powm( y, sk->g, sk->x, sk->p );
- rc = !mpi_cmp( y, sk->y );
- mpi_free( y );
- return rc;
-}
-
-
-static void
-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 );
- 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 );
- 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 */
- 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(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 );
- 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(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 */
- 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; 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 */
- 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 ; 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 GCRYERR_INV_PK_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 GCRYERR_INV_PK_ALGO;
- if( !skey[0] || !skey[1] || !skey[2] || !skey[3] )
- return GCRYERR_BAD_MPI;
-
- sk.p = skey[0];
- sk.g = skey[1];
- sk.y = skey[2];
- sk.x = skey[3];
- if( !check_secret_key( &sk ) )
- return GCRYERR_BAD_SECRET_KEY;
-
- return 0;
-}
-
-
-
-int
-elg_encrypt( int algo, MPI *resarr, MPI data, MPI *pkey )
-{
- ELG_public_key pk;
-
- if( !is_ELGAMAL(algo) )
- return GCRYERR_INV_PK_ALGO;
- if( !data || !pkey[0] || !pkey[1] || !pkey[2] )
- return GCRYERR_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 ) );
- 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 GCRYERR_INV_PK_ALGO;
- if( !data[0] || !data[1]
- || !skey[0] || !skey[1] || !skey[2] || !skey[3] )
- return GCRYERR_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 GCRYERR_INV_PK_ALGO;
- if( !data || !skey[0] || !skey[1] || !skey[2] || !skey[3] )
- return GCRYERR_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 GCRYERR_INV_PK_ALGO;
- if( !data[0] || !data[1] || !hash
- || !pkey[0] || !pkey[1] || !pkey[2] )
- return GCRYERR_BAD_MPI;
-
- pk.p = pkey[0];
- pk.g = pkey[1];
- pk.y = pkey[2];
- if( !verify( data[0], data[1], hash, &pk ) )
- return GCRYERR_BAD_SIGNATURE;
- 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 GCRY_PK_ELG:
- *use = GCRY_PK_USAGE_SIGN|GCRY_PK_USAGE_ENCR;
- return "ELG";
- case GCRY_PK_ELG_E:
- *use = GCRY_PK_USAGE_SIGN|GCRY_PK_USAGE_ENCR;
- return "ELG-E";
- default: *use = 0; return NULL;
- }
-}
-
-
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