grub2 (1.98+20100804-14+squeeze1) lib/libgcrypt-grub/cipher/elgamal.c

Summary

 lib/libgcrypt-grub/cipher/elgamal.c |  844 ++++++++++++++++++++++++++++++++++++
 1 file changed, 844 insertions(+)

    
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Patch contents

--- grub2-1.98+20100804.orig/lib/libgcrypt-grub/cipher/elgamal.c
+++ grub2-1.98+20100804/lib/libgcrypt-grub/cipher/elgamal.c
@@ -0,0 +1,844 @@
+/* This file was automatically imported with 
+   import_gcry.py. Please don't modify it */
+/* 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 <http://www.gnu.org/licenses/>.
+ *
+ * For a description of the algorithm, see:
+ *   Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
+ *   ISBN 0-471-11709-9. Pages 476 ff.
+ */
+
+#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
+  };
+