Initial revision

1 files changed, 1028 insertions, 0 deletions

diff --git a/pwmanager/libcrypt/cipher/primegen.c b/pwmanager/libcrypt/cipher/primegen.c
new file mode 100644
index 0000000..afd435e
--- a/dev/null
+++ b/pwmanager/libcrypt/cipher/primegen.c
@@ -0,0 +1,1028 @@
+/* primegen.c - prime number generator
+ * Copyright (C) 1998, 2000, 2001, 2002, 2003
+ *               2004 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ *
+ * ***********************************************************************
+ * The algorithm used to generate practically save primes is due to
+ * Lim and Lee as described in the CRYPTO '97 proceedings (ISBN3540633847)
+ * page 260.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <errno.h>
+
+#include "g10lib.h"
+#include "mpi.h"
+#include "cipher.h"
+
+static gcry_mpi_t gen_prime (unsigned int nbits, int secret, int randomlevel, 
+                             int (*extra_check)(void *, gcry_mpi_t),
+                             void *extra_check_arg);
+static int check_prime( gcry_mpi_t prime, gcry_mpi_t val_2,
+                        gcry_prime_check_func_t cb_func, void *cb_arg );
+static int is_prime( gcry_mpi_t n, int steps, int *count );
+static void m_out_of_n( char *array, int m, int n );
+
+static void (*progress_cb) (void *,const char*,int,int, int );
+static void *progress_cb_data;
+
+/* Note: 2 is not included because it can be tested more easily by
+   looking at bit 0. The last entry in this list is marked by a zero */
+static ushort small_prime_numbers[] = {
+    3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43,
+    47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101,
+    103, 107, 109, 113, 127, 131, 137, 139, 149, 151,
+    157, 163, 167, 173, 179, 181, 191, 193, 197, 199,
+    211, 223, 227, 229, 233, 239, 241, 251, 257, 263,
+    269, 271, 277, 281, 283, 293, 307, 311, 313, 317,
+    331, 337, 347, 349, 353, 359, 367, 373, 379, 383,
+    389, 397, 401, 409, 419, 421, 431, 433, 439, 443,
+    449, 457, 461, 463, 467, 479, 487, 491, 499, 503,
+    509, 521, 523, 541, 547, 557, 563, 569, 571, 577,
+    587, 593, 599, 601, 607, 613, 617, 619, 631, 641,
+    643, 647, 653, 659, 661, 673, 677, 683, 691, 701,
+    709, 719, 727, 733, 739, 743, 751, 757, 761, 769,
+    773, 787, 797, 809, 811, 821, 823, 827, 829, 839,
+    853, 857, 859, 863, 877, 881, 883, 887, 907, 911,
+    919, 929, 937, 941, 947, 953, 967, 971, 977, 983,
+    991, 997, 1009, 1013, 1019, 1021, 1031, 1033,
+    1039, 1049, 1051, 1061, 1063, 1069, 1087, 1091,
+    1093, 1097, 1103, 1109, 1117, 1123, 1129, 1151,
+    1153, 1163, 1171, 1181, 1187, 1193, 1201, 1213,
+    1217, 1223, 1229, 1231, 1237, 1249, 1259, 1277,
+    1279, 1283, 1289, 1291, 1297, 1301, 1303, 1307,
+    1319, 1321, 1327, 1361, 1367, 1373, 1381, 1399,
+    1409, 1423, 1427, 1429, 1433, 1439, 1447, 1451,
+    1453, 1459, 1471, 1481, 1483, 1487, 1489, 1493,
+    1499, 1511, 1523, 1531, 1543, 1549, 1553, 1559,
+    1567, 1571, 1579, 1583, 1597, 1601, 1607, 1609,
+    1613, 1619, 1621, 1627, 1637, 1657, 1663, 1667,
+    1669, 1693, 1697, 1699, 1709, 1721, 1723, 1733,
+    1741, 1747, 1753, 1759, 1777, 1783, 1787, 1789,
+    1801, 1811, 1823, 1831, 1847, 1861, 1867, 1871,
+    1873, 1877, 1879, 1889, 1901, 1907, 1913, 1931,
+    1933, 1949, 1951, 1973, 1979, 1987, 1993, 1997,
+    1999, 2003, 2011, 2017, 2027, 2029, 2039, 2053,
+    2063, 2069, 2081, 2083, 2087, 2089, 2099, 2111,
+    2113, 2129, 2131, 2137, 2141, 2143, 2153, 2161,
+    2179, 2203, 2207, 2213, 2221, 2237, 2239, 2243,
+    2251, 2267, 2269, 2273, 2281, 2287, 2293, 2297,
+    2309, 2311, 2333, 2339, 2341, 2347, 2351, 2357,
+    2371, 2377, 2381, 2383, 2389, 2393, 2399, 2411,
+    2417, 2423, 2437, 2441, 2447, 2459, 2467, 2473,
+    2477, 2503, 2521, 2531, 2539, 2543, 2549, 2551,
+    2557, 2579, 2591, 2593, 2609, 2617, 2621, 2633,
+    2647, 2657, 2659, 2663, 2671, 2677, 2683, 2687,
+    2689, 2693, 2699, 2707, 2711, 2713, 2719, 2729,
+    2731, 2741, 2749, 2753, 2767, 2777, 2789, 2791,
+    2797, 2801, 2803, 2819, 2833, 2837, 2843, 2851,
+    2857, 2861, 2879, 2887, 2897, 2903, 2909, 2917,
+    2927, 2939, 2953, 2957, 2963, 2969, 2971, 2999,
+    3001, 3011, 3019, 3023, 3037, 3041, 3049, 3061,
+    3067, 3079, 3083, 3089, 3109, 3119, 3121, 3137,
+    3163, 3167, 3169, 3181, 3187, 3191, 3203, 3209,
+    3217, 3221, 3229, 3251, 3253, 3257, 3259, 3271,
+    3299, 3301, 3307, 3313, 3319, 3323, 3329, 3331,
+    3343, 3347, 3359, 3361, 3371, 3373, 3389, 3391,
+    3407, 3413, 3433, 3449, 3457, 3461, 3463, 3467,
+    3469, 3491, 3499, 3511, 3517, 3527, 3529, 3533,
+    3539, 3541, 3547, 3557, 3559, 3571, 3581, 3583,
+    3593, 3607, 3613, 3617, 3623, 3631, 3637, 3643,
+    3659, 3671, 3673, 3677, 3691, 3697, 3701, 3709,
+    3719, 3727, 3733, 3739, 3761, 3767, 3769, 3779,
+    3793, 3797, 3803, 3821, 3823, 3833, 3847, 3851,
+    3853, 3863, 3877, 3881, 3889, 3907, 3911, 3917,
+    3919, 3923, 3929, 3931, 3943, 3947, 3967, 3989,
+    4001, 4003, 4007, 4013, 4019, 4021, 4027, 4049,
+    4051, 4057, 4073, 4079, 4091, 4093, 4099, 4111,
+    4127, 4129, 4133, 4139, 4153, 4157, 4159, 4177,
+    4201, 4211, 4217, 4219, 4229, 4231, 4241, 4243,
+    4253, 4259, 4261, 4271, 4273, 4283, 4289, 4297,
+    4327, 4337, 4339, 4349, 4357, 4363, 4373, 4391,
+    4397, 4409, 4421, 4423, 4441, 4447, 4451, 4457,
+    4463, 4481, 4483, 4493, 4507, 4513, 4517, 4519,
+    4523, 4547, 4549, 4561, 4567, 4583, 4591, 4597,
+    4603, 4621, 4637, 4639, 4643, 4649, 4651, 4657,
+    4663, 4673, 4679, 4691, 4703, 4721, 4723, 4729,
+    4733, 4751, 4759, 4783, 4787, 4789, 4793, 4799,
+    4801, 4813, 4817, 4831, 4861, 4871, 4877, 4889,
+    4903, 4909, 4919, 4931, 4933, 4937, 4943, 4951,
+    4957, 4967, 4969, 4973, 4987, 4993, 4999,
+    0
+};
+static int no_of_small_prime_numbers = DIM (small_prime_numbers) - 1;
+
+void
+_gcry_register_primegen_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, "primegen", c, 0, 0 );
+}
+
+
+/****************
+ * Generate a prime number (stored in secure memory)
+ */
+gcry_mpi_t
+_gcry_generate_secret_prime (unsigned int nbits,
+                             int (*extra_check)(void*, gcry_mpi_t),
+                             void *extra_check_arg)
+{
+  gcry_mpi_t prime;
+
+  prime = gen_prime( nbits, 1, 2, extra_check, extra_check_arg);
+  progress('\n');
+  return prime;
+}
+
+gcry_mpi_t
+_gcry_generate_public_prime( unsigned int nbits,
+                             int (*extra_check)(void*, gcry_mpi_t),
+                             void *extra_check_arg)
+{
+  gcry_mpi_t prime;
+
+  prime = gen_prime( nbits, 0, 2, extra_check, extra_check_arg );
+  progress('\n');
+  return prime;
+}
+
+
+/****************
+ * We do not need to use the strongest RNG because we gain no extra
+ * security from it - The prime number is public and we could also
+ * offer the factors for those who are willing to check that it is
+ * indeed a strong prime.  With ALL_FACTORS set to true all afcors of
+ * prime-1 are returned in FACTORS.
+ *
+ * mode 0: Standard
+         *1: Make sure that at least one factor is of size qbits.
+ */
+static gcry_err_code_t
+prime_generate_internal (int mode,
+                         gcry_mpi_t *prime_generated, unsigned int pbits,
+                         unsigned int qbits, gcry_mpi_t g,
+                         gcry_mpi_t **ret_factors,
+                         gcry_random_level_t randomlevel, unsigned int flags,
+                         int all_factors,
+                         gcry_prime_check_func_t cb_func, void *cb_arg)
+{
+  gcry_err_code_t err = 0;
+  gcry_mpi_t *factors_new = NULL; /* Factors to return to the
+                                     caller.  */
+          gcry_mpi_t *factors = NULL;/* Current factors.  */
+          gcry_mpi_t *pool = NULL;/* Pool of primes.  */
+          unsigned char *perms = NULL;/* Permutations of POOL.  */
+          gcry_mpi_t q_factor = NULL;/* Used if QBITS is non-zero.  */
+          unsigned int fbits = 0;/* Length of prime factors.  */
+          unsigned int n = 0;   /* Number of factors.  */
+          unsigned int m = 0;   /* Number of primes in pool.  */
+          gcry_mpi_t q = NULL;  /* First prime factor.  */
+          gcry_mpi_t prime = NULL;/* Prime candidate.  */
+          unsigned int nprime = 0;/* Bits of PRIME.  */
+  unsigned int req_qbits;       /* The original QBITS value.  */
+  gcry_mpi_t val_2;             /* For check_prime().  */
+  unsigned int is_secret = (flags & GCRY_PRIME_FLAG_SECRET);
+  unsigned int count1 = 0, count2 = 0;
+  unsigned int i = 0, j = 0;
+
+  if (pbits < 48)
+    return GPG_ERR_INV_ARG;
+
+  /* If QBITS is not given, assume a reasonable value. */
+  if (!qbits)
+    qbits = pbits / 3;
+
+  req_qbits = qbits;
+
+  /* Find number of needed prime factors.  */
+  for (n = 1; (pbits - qbits - 1) / n  >= qbits; n++)
+    ;
+  n--;
+
+  val_2 = mpi_alloc_set_ui (2);
+
+  if ((! n) || ((mode == 1) && (n < 2)))
+    {
+      err = GPG_ERR_INV_ARG;
+      goto leave;
+    }
+
+  if (mode == 1)
+    {
+      n--;
+      fbits = (pbits - 2 * req_qbits -1) / n;
+      qbits =  pbits - req_qbits - n * fbits;
+    }
+  else
+    {
+      fbits = (pbits - req_qbits -1) / n;
+      qbits = pbits - n * fbits;
+    }
+  
+  if (DBG_CIPHER)
+    log_debug ("gen prime: pbits=%u qbits=%u fbits=%u/%u n=%d\n",
+               pbits, req_qbits, qbits, fbits, n);
+
+  prime = gcry_mpi_new (pbits);
+
+  /* Generate first prime factor.  */
+  q = gen_prime (qbits, is_secret, randomlevel, NULL, NULL);
+  
+  if (mode == 1)
+    q_factor = gen_prime (req_qbits, is_secret, randomlevel, NULL, NULL);
+  
+  /* Allocate an array to hold the factors + 2 for later usage.  */
+  factors = gcry_calloc (n + 2, sizeof (*factors));
+  if (!factors)
+    {
+      err = gpg_err_code_from_errno (errno);
+      goto leave;
+    }
+      
+  /* Make a pool of 3n+5 primes (this is an arbitrary value).  */
+  m = n * 3 + 5;
+  if (mode == 1) /* Need some more (for e.g. DSA).  */
+    m += 5;
+  if (m < 25)
+    m = 25;
+  pool = gcry_calloc (m , sizeof (*pool));
+  if (! pool)
+    {
+      err = gpg_err_code_from_errno (errno);
+      goto leave;
+    }
+
+  /* Permutate over the pool of primes.  */
+  do
+    {
+    next_try:
+      if (! perms)
+        {
+          /* Allocate new primes.  */
+          for(i = 0; i < m; i++)
+            {
+              mpi_free (pool[i]);
+              pool[i] = NULL;
+            }
+
+          /* Init m_out_of_n().  */
+          perms = gcry_calloc (1, m);
+          if (! perms)
+            {
+              err = gpg_err_code_from_errno (errno);
+              goto leave;
+            }
+          for(i = 0; i < n; i++)
+            {
+              perms[i] = 1;
+              pool[i] = gen_prime (fbits, is_secret,
+                                   randomlevel, NULL, NULL);
+              factors[i] = pool[i];
+            }
+        }
+      else
+        {
+          m_out_of_n (perms, n, m);
+          for (i = j = 0; (i < m) && (j < n); i++)
+            if (perms[i])
+              {
+                if(! pool[i])
+                  pool[i] = gen_prime (fbits, 0, 1, NULL, NULL);
+                factors[j++] = pool[i];
+              }
+          if (i == n)
+            {
+              gcry_free (perms);
+              perms = NULL;
+              progress ('!');
+                      goto next_try;/* Allocate new primes.  */
+            }
+        }
+
+        /* Generate next prime candidate:
+           p = 2 * q [ * q_factor] * factor_0 * factor_1 * ... * factor_n + 1. 
+        */
+        mpi_set (prime, q);
+        mpi_mul_ui (prime, prime, 2);
+        if (mode == 1)
+          mpi_mul (prime, prime, q_factor);
+        for(i = 0; i < n; i++)
+          mpi_mul (prime, prime, factors[i]);
+        mpi_add_ui (prime, prime, 1);
+        nprime = mpi_get_nbits (prime);
+
+        if (nprime < pbits)
+          {
+            if (++count1 > 20)
+              {
+                count1 = 0;
+                qbits++;
+                progress('>');
+                mpi_free (q);
+                q = gen_prime (qbits, 0, 0, NULL, NULL);
+                goto next_try;
+              }
+          }
+        else
+          count1 = 0;
+        
+        if (nprime > pbits)
+          {
+            if (++count2 > 20)
+              {
+                count2 = 0;
+                qbits--;
+                progress('<');
+                mpi_free (q);
+                q = gen_prime (qbits, 0, 0, NULL, NULL);
+                goto next_try;
+              }
+          }
+        else
+          count2 = 0;
+    }
+  while (! ((nprime == pbits) && check_prime (prime, val_2, cb_func, cb_arg)));
+
+  if (DBG_CIPHER)
+    {
+      progress ('\n');
+      log_mpidump ("prime    : ", prime);
+      log_mpidump ("factor  q: ", q);
+      if (mode == 1)
+        log_mpidump ("factor q0: ", q_factor);
+      for (i = 0; i < n; i++)
+        log_mpidump ("factor pi: ", factors[i]);
+      log_debug ("bit sizes: prime=%u, q=%u",
+                 mpi_get_nbits (prime), mpi_get_nbits (q));
+      if (mode == 1)
+        log_debug (", q0=%u", mpi_get_nbits (q_factor));
+      for (i = 0; i < n; i++)
+        log_debug (", p%d=%u", i, mpi_get_nbits (factors[i]));
+      progress('\n');
+    }
+
+  if (ret_factors)
+    {
+      /* Caller wants the factors.  */
+      factors_new = gcry_calloc (n + 4, sizeof (*factors_new));
+      if (! factors_new)
+        {
+          err = gpg_err_code_from_errno (errno);
+          goto leave;
+        }
+
+      if (all_factors)
+        {
+          i = 0;
+          factors_new[i++] = gcry_mpi_set_ui (NULL, 2);
+          factors_new[i++] = mpi_copy (q);
+          if (mode == 1)
+            factors_new[i++] = mpi_copy (q_factor);
+          for(j=0; j < n; j++)
+            factors_new[i++] = mpi_copy (factors[j]);
+        }
+      else
+        {
+          i = 0;
+          if (mode == 1)
+            {
+              factors_new[i++] = mpi_copy (q_factor);
+              for (; i <= n; i++)
+                factors_new[i] = mpi_copy (factors[i]);
+            }
+          else
+            for (; i < n; i++ )
+              factors_new[i] = mpi_copy (factors[i]);
+        }
+    }
+  
+  if (g)
+    {
+      /* Create a generator (start with 3).  */
+      gcry_mpi_t tmp = mpi_alloc (mpi_get_nlimbs (prime));
+      gcry_mpi_t b = mpi_alloc (mpi_get_nlimbs (prime));
+      gcry_mpi_t pmin1 = mpi_alloc (mpi_get_nlimbs (prime));
+      
+      if (mode == 1)
+        err = GPG_ERR_NOT_IMPLEMENTED;
+      else
+        {
+          factors[n] = q;
+          factors[n + 1] = mpi_alloc_set_ui (2);
+          mpi_sub_ui (pmin1, prime, 1);
+          mpi_set_ui (g, 2);
+          do
+            {
+              mpi_add_ui (g, g, 1);
+              if (DBG_CIPHER)
+                {
+                  log_debug ("checking g:");
+                  gcry_mpi_dump (g);
+                  log_printf ("\n");
+                }
+              else
+                progress('^');
+              for (i = 0; i < n + 2; i++)
+                {
+                  mpi_fdiv_q (tmp, pmin1, factors[i]);
+                  /* No mpi_pow(), but it is okay to use this with mod
+                     prime.  */
+                  gcry_mpi_powm (b, g, tmp, prime);
+                  if (! mpi_cmp_ui (b, 1))
+                    break;
+                }
+              if (DBG_CIPHER)
+                progress('\n');
+            } 
+          while (i < n + 2);
+
+          mpi_free (factors[n+1]);
+          mpi_free (tmp);
+          mpi_free (b);
+          mpi_free (pmin1);
+        }
+    }
+  
+  if (! DBG_CIPHER)
+    progress ('\n');
+
+
+ leave:
+  if (pool)
+    {
+      for(i = 0; i < m; i++)
+        mpi_free (pool[i]);
+      gcry_free (pool);
+    }
+  if (factors)
+    gcry_free (factors);  /* Factors are shallow copies.  */
+  if (perms)
+    gcry_free (perms);
+
+  mpi_free (val_2);
+  mpi_free (q);
+  mpi_free (q_factor);
+
+  if (! err)
+    {
+      *prime_generated = prime;
+      if (ret_factors)
+        *ret_factors = factors_new;
+    }
+  else
+    {
+      if (factors_new)
+        {
+          for (i = 0; factors_new[i]; i++)
+            mpi_free (factors_new[i]);
+          gcry_free (factors_new);
+        }
+      mpi_free (prime);
+    }
+
+  return err;
+}
+
+gcry_mpi_t
+_gcry_generate_elg_prime (int mode, unsigned pbits, unsigned qbits,
+                          gcry_mpi_t g, gcry_mpi_t **ret_factors)
+{
+  gcry_err_code_t err = GPG_ERR_NO_ERROR;
+  gcry_mpi_t prime = NULL;
+  
+  err = prime_generate_internal (mode, &prime, pbits, qbits, g,
+                                 ret_factors, GCRY_WEAK_RANDOM, 0, 0,
+                                 NULL, NULL);
+
+  return prime;
+}
+
+static gcry_mpi_t
+gen_prime (unsigned int nbits, int secret, int randomlevel, 
+           int (*extra_check)(void *, gcry_mpi_t), void *extra_check_arg)
+{
+  gcry_mpi_t prime, ptest, pminus1, val_2, val_3, result;
+  int i;
+  unsigned x, step;
+  unsigned count1, count2;
+  int *mods;
+  
+/*   if (  DBG_CIPHER ) */
+/*     log_debug ("generate a prime of %u bits ", nbits ); */
+
+  if (nbits < 16)
+    log_fatal ("can't generate a prime with less than %d bits\n", 16);
+
+  mods = gcry_xmalloc( no_of_small_prime_numbers * sizeof *mods );
+  /* Make nbits fit into gcry_mpi_t implementation. */
+  val_2  = mpi_alloc_set_ui( 2 );
+  val_3 = mpi_alloc_set_ui( 3);
+  prime  = secret? gcry_mpi_snew ( nbits ): gcry_mpi_new ( nbits );
+  result = mpi_alloc_like( prime );
+  pminus1= mpi_alloc_like( prime );
+  ptest  = mpi_alloc_like( prime );
+  count1 = count2 = 0;
+  for (;;)
+    {  /* try forvever */
+      int dotcount=0;
+      
+      /* generate a random number */
+      gcry_mpi_randomize( prime, nbits, randomlevel );
+      
+      /* Set high order bit to 1, set low order bit to 1.  If we are
+         generating a secret prime we are most probably doing that
+         for RSA, to make sure that the modulus does have the
+         requested key size we set the 2 high order bits. */
+      mpi_set_highbit (prime, nbits-1);
+      if (secret)
+        mpi_set_bit (prime, nbits-2);
+      mpi_set_bit(prime, 0);
+      
+      /* Calculate all remainders. */
+      for (i=0; (x = small_prime_numbers[i]); i++ )
+        mods[i] = mpi_fdiv_r_ui(NULL, prime, x);
+      
+      /* Now try some primes starting with prime. */
+      for(step=0; step < 20000; step += 2 ) 
+        {
+          /* Check against all the small primes we have in mods. */
+          count1++;
+          for (i=0; (x = small_prime_numbers[i]); i++ ) 
+            {
+              while ( mods[i] + step >= x )
+                mods[i] -= x;
+              if ( !(mods[i] + step) )
+                break;
+            }
+          if ( x )
+            continue;   /* Found a multiple of an already known prime. */
+          
+          mpi_add_ui( ptest, prime, step );
+
+          /* Do a fast Fermat test now. */
+          count2++;
+          mpi_sub_ui( pminus1, ptest, 1);
+          gcry_mpi_powm( result, val_2, pminus1, ptest );
+          if ( !mpi_cmp_ui( result, 1 ) )
+            { 
+              /* Not composite, perform stronger tests */
+              if (is_prime(ptest, 5, &count2 ))
+                {
+                  if (!mpi_test_bit( ptest, nbits-1-secret ))
+                    {
+                      progress('\n');
+                      log_debug ("overflow in prime generation\n");
+                      break; /* Stop loop, continue with a new prime. */
+                    }
+
+                  if (extra_check && extra_check (extra_check_arg, ptest))
+                    { 
+                      /* The extra check told us that this prime is
+                         not of the caller's taste. */
+                      progress ('/');
+                    }
+                  else
+                    { 
+                      /* Got it. */
+                      mpi_free(val_2);
+                      mpi_free(val_3);
+                      mpi_free(result);
+                      mpi_free(pminus1);
+                      mpi_free(prime);
+                      gcry_free(mods);
+                      return ptest; 
+                    }
+                }
+            }
+          if (++dotcount == 10 )
+            {
+              progress('.');
+              dotcount = 0;
+            }
+        }
+      progress(':'); /* restart with a new random value */
+    }
+}
+
+/****************
+ * Returns: true if this may be a prime
+ */
+static int
+check_prime( gcry_mpi_t prime, gcry_mpi_t val_2,
+             gcry_prime_check_func_t cb_func, void *cb_arg)
+{
+  int i;
+  unsigned int x;
+  int count=0;
+
+  /* Check against small primes. */
+  for (i=0; (x = small_prime_numbers[i]); i++ )
+    {
+      if ( mpi_divisible_ui( prime, x ) )
+        return 0;
+    }
+
+  /* A quick Fermat test. */
+  {
+    gcry_mpi_t result = mpi_alloc_like( prime );
+    gcry_mpi_t pminus1 = mpi_alloc_like( prime );
+    mpi_sub_ui( pminus1, prime, 1);
+    gcry_mpi_powm( result, val_2, pminus1, prime );
+    mpi_free( pminus1 );
+    if ( mpi_cmp_ui( result, 1 ) )
+      { 
+        /* Is composite. */
+        mpi_free( result );
+        progress('.');
+        return 0;
+      }
+    mpi_free( result );
+  }
+
+  if (!cb_func || cb_func (cb_arg, GCRY_PRIME_CHECK_AT_MAYBE_PRIME, prime))
+    {
+      /* Perform stronger tests. */
+      if ( is_prime( prime, 5, &count ) )
+        {
+          if (!cb_func
+              || cb_func (cb_arg, GCRY_PRIME_CHECK_AT_GOT_PRIME, prime))
+            return 1; /* Probably a prime. */
+        }
+    }
+  progress('.');
+  return 0;
+}
+
+
+/*
+ * Return true if n is probably a prime
+ */
+static int
+is_prime (gcry_mpi_t n, int steps, int *count)
+{
+  gcry_mpi_t x = mpi_alloc( mpi_get_nlimbs( n ) );
+  gcry_mpi_t y = mpi_alloc( mpi_get_nlimbs( n ) );
+  gcry_mpi_t z = mpi_alloc( mpi_get_nlimbs( n ) );
+  gcry_mpi_t nminus1 = mpi_alloc( mpi_get_nlimbs( n ) );
+  gcry_mpi_t a2 = mpi_alloc_set_ui( 2 );
+  gcry_mpi_t q;
+  unsigned i, j, k;
+  int rc = 0;
+  unsigned nbits = mpi_get_nbits( n );
+
+  mpi_sub_ui( nminus1, n, 1 );
+
+  /* Find q and k, so that n = 1 + 2^k * q . */
+  q = mpi_copy ( nminus1 );
+  k = mpi_trailing_zeros ( q );
+  mpi_tdiv_q_2exp (q, q, k);
+
+  for (i=0 ; i < steps; i++ )
+    {
+      ++*count;
+      if( !i )
+        {
+          mpi_set_ui( x, 2 );
+        }
+      else
+        {
+          gcry_mpi_randomize( x, nbits, GCRY_WEAK_RANDOM );
+
+          /* Make sure that the number is smaller than the prime and
+             keep the randomness of the high bit. */
+          if ( mpi_test_bit ( x, nbits-2) )
+            {
+              mpi_set_highbit ( x, nbits-2); /* Clear all higher bits. */
+            }
+          else
+            {
+              mpi_set_highbit( x, nbits-2 );
+              mpi_clear_bit( x, nbits-2 );
+            }
+          assert ( mpi_cmp( x, nminus1 ) < 0 && mpi_cmp_ui( x, 1 ) > 0 );
+        }
+      gcry_mpi_powm ( y, x, q, n);
+      if ( mpi_cmp_ui(y, 1) && mpi_cmp( y, nminus1 ) )
+        {
+          for ( j=1; j < k && mpi_cmp( y, nminus1 ); j++ )
+            {
+              gcry_mpi_powm(y, y, a2, n);
+              if( !mpi_cmp_ui( y, 1 ) )
+                goto leave; /* Not a prime. */
+            }
+          if (mpi_cmp( y, nminus1 ) )
+            goto leave; /* Not a prime. */
+        }
+      progress('+');
+    }
+  rc = 1; /* May be a prime. */
+
+ leave:
+  mpi_free( x );
+  mpi_free( y );
+  mpi_free( z );
+  mpi_free( nminus1 );
+  mpi_free( q );
+  mpi_free( a2 );
+
+  return rc;
+}
+
+
+static void
+m_out_of_n ( char *array, int m, int n )
+{
+  int i=0, i1=0, j=0, jp=0,  j1=0, k1=0, k2=0;
+
+  if( !m || m >= n )
+    return;
+
+  if( m == 1 )
+    { 
+      /* Special case. */
+      for (i=0; i < n; i++ )
+        {
+          if( array[i] )
+            {
+              array[i++] = 0;
+              if( i >= n )
+                i = 0;
+              array[i] = 1;
+              return;
+            }
+        }
+      BUG();
+    }
+
+  for (j=1; j < n; j++ )
+    {
+      if ( array[n-1] == array[n-j-1])
+        continue;
+      j1 = j;
+      break;
+    }
+
+  if ( (m & 1) )
+    {
+      /* M is odd. */
+      if( array[n-1] )
+        {
+          if( j1 & 1 )
+            {
+              k1 = n - j1;
+              k2 = k1+2;
+              if( k2 > n )
+                k2 = n;
+              goto leave;
+            }
+          goto scan;
+        }
+      k2 = n - j1 - 1;
+      if( k2 == 0 )
+        {
+          k1 = i;
+          k2 = n - j1;
+        }
+      else if( array[k2] && array[k2-1] )
+        k1 = n;
+      else
+        k1 = k2 + 1;
+    }
+  else 
+    {
+      /* M is even. */
+      if( !array[n-1] )
+        {
+          k1 = n - j1;
+          k2 = k1 + 1;
+          goto leave;
+        }
+        
+      if( !(j1 & 1) )
+        {
+          k1 = n - j1;
+          k2 = k1+2;
+          if( k2 > n )
+            k2 = n;
+          goto leave;
+        }
+    scan:
+      jp = n - j1 - 1;
+      for (i=1; i <= jp; i++ ) 
+        {
+          i1 = jp + 2 - i;
+          if( array[i1-1]  )
+            {
+              if( array[i1-2] )
+                {
+                  k1 = i1 - 1;
+                  k2 = n - j1;
+                }
+              else
+                {
+                  k1 = i1 - 1;
+                  k2 = n + 1 - j1;
+                }
+              goto leave;
+            }
+        }
+      k1 = 1;
+      k2 = n + 1 - m;
+    }
+ leave:
+  array[k1-1] = !array[k1-1];
+  array[k2-1] = !array[k2-1];
+}
+
+
+/* Generate a new prime number of PRIME_BITS bits and store it in
+   PRIME.  If FACTOR_BITS is non-zero, one of the prime factors of
+   (prime - 1) / 2 must be FACTOR_BITS bits long.  If FACTORS is
+   non-zero, allocate a new, NULL-terminated array holding the prime
+   factors and store it in FACTORS.  FLAGS might be used to influence
+   the prime number generation process.  */
+gcry_error_t
+gcry_prime_generate (gcry_mpi_t *prime, unsigned int prime_bits,
+                     unsigned int factor_bits, gcry_mpi_t **factors,
+                     gcry_prime_check_func_t cb_func, void *cb_arg,
+                     gcry_random_level_t random_level,
+                     unsigned int flags)
+{
+  gcry_err_code_t err = GPG_ERR_NO_ERROR;
+  gcry_mpi_t *factors_generated = NULL;
+  gcry_mpi_t prime_generated = NULL;
+  unsigned int mode = 0;
+
+  if (!prime)
+    return gpg_error (GPG_ERR_INV_ARG);
+  *prime = NULL; 
+
+  if (flags & GCRY_PRIME_FLAG_SPECIAL_FACTOR)
+    mode = 1;
+
+  /* Generate.  */
+  err = prime_generate_internal (mode, &prime_generated, prime_bits,
+                                 factor_bits, NULL,
+                                 factors? &factors_generated : NULL,
+                                 random_level, flags, 1,
+                                 cb_func, cb_arg);
+
+  if (! err)
+    if (cb_func)
+      {
+        /* Additional check. */
+        if ( !cb_func (cb_arg, GCRY_PRIME_CHECK_AT_FINISH, prime_generated))
+          {
+            /* Failed, deallocate resources.  */
+            unsigned int i;
+
+            mpi_free (prime_generated);
+            if (factors)
+              {
+                for (i = 0; factors_generated[i]; i++)
+                  mpi_free (factors_generated[i]);
+                gcry_free (factors_generated);
+              }
+            err = GPG_ERR_GENERAL; 
+          }
+      }
+
+  if (! err)
+    {
+      if (factors)
+        *factors = factors_generated;
+      *prime = prime_generated;
+    }
+
+  return gcry_error (err);
+}
+
+/* Check wether the number X is prime.  */
+gcry_error_t
+gcry_prime_check (gcry_mpi_t x, unsigned int flags)
+{
+  gcry_err_code_t err = GPG_ERR_NO_ERROR;
+  gcry_mpi_t val_2 = mpi_alloc_set_ui (2); /* Used by the Fermat test. */
+
+  if (! check_prime (x, val_2, NULL, NULL))
+    err = GPG_ERR_NO_PRIME;
+
+  mpi_free (val_2);
+
+  return gcry_error (err);
+}
+
+/* Find a generator for PRIME where the factorization of (prime-1) is
+   in the NULL terminated array FACTORS. Return the generator as a
+   newly allocated MPI in R_G.  If START_G is not NULL, use this as s
+   atart for the search. Returns 0 on success.*/
+gcry_error_t
+gcry_prime_group_generator (gcry_mpi_t *r_g,
+                            gcry_mpi_t prime, gcry_mpi_t *factors,
+                            gcry_mpi_t start_g)
+{
+  gcry_mpi_t tmp = gcry_mpi_new (0);
+  gcry_mpi_t b = gcry_mpi_new (0);
+  gcry_mpi_t pmin1 = gcry_mpi_new (0);
+  gcry_mpi_t g = start_g? gcry_mpi_copy (start_g) : gcry_mpi_set_ui (NULL, 3);
+  int first = 1;
+  int i, n;
+
+  if (!factors || !r_g || !prime)
+    return gpg_error (GPG_ERR_INV_ARG);
+  *r_g = NULL; 
+
+  for (n=0; factors[n]; n++)
+    ;
+  if (n < 2)
+    return gpg_error (GPG_ERR_INV_ARG);
+
+  /* Extra sanity check - usually disabled. */  
+/*   mpi_set (tmp, factors[0]); */
+/*   for(i = 1; i < n; i++) */
+/*     mpi_mul (tmp, tmp, factors[i]); */
+/*   mpi_add_ui (tmp, tmp, 1); */
+/*   if (mpi_cmp (prime, tmp)) */
+/*     return gpg_error (GPG_ERR_INV_ARG); */
+  
+  gcry_mpi_sub_ui (pmin1, prime, 1);      
+  do         
+    {
+      if (first)
+        first = 0;
+      else
+        gcry_mpi_add_ui (g, g, 1);
+      
+      if (DBG_CIPHER)
+        {
+          log_debug ("checking g:");
+          gcry_mpi_dump (g);
+          log_debug ("\n");
+        }
+      else
+        progress('^');
+      
+      for (i = 0; i < n; i++)
+        {
+          mpi_fdiv_q (tmp, pmin1, factors[i]);
+          gcry_mpi_powm (b, g, tmp, prime);
+          if (! mpi_cmp_ui (b, 1))
+            break;
+        }
+      if (DBG_CIPHER)
+        progress('\n');
+    }
+  while (i < n);
+  
+  gcry_mpi_release (tmp);
+  gcry_mpi_release (b); 
+  gcry_mpi_release (pmin1); 
+  *r_g = g; 
+
+  return 0; 
+}
+
+/* Convenience function to release the factors array. */
+void
+gcry_prime_release_factors (gcry_mpi_t *factors)
+{
+  if (factors)
+    {
+      int i;
+      
+      for (i=0; factors[i]; i++)
+        mpi_free (factors[i]);
+      gcry_free (factors);
+    }
+}