1 files changed, 134 insertions, 0 deletions
diff --git a/src/math/dsa_gen.cpp b/src/math/dsa_gen.cpp
new file mode 100644
index 000000000..baaba66ee
--- /dev/null
+++ b/src/math/dsa_gen.cpp
@@ -0,0 +1,134 @@
+/*************************************************
+* DSA Parameter Generation Source File           *
+* (C) 1999-2007 Jack Lloyd                       *
+*************************************************/
+
+#include <botan/dl_group.h>
+#include <botan/numthry.h>
+#include <botan/lookup.h>
+#include <botan/parsing.h>
+#include <algorithm>
+#include <memory>
+
+namespace Botan {
+
+namespace {
+
+/*************************************************
+* Check if this size is allowed by FIPS 186-3    *
+*************************************************/
+bool fips186_3_valid_size(u32bit pbits, u32bit qbits)
+   {
+   if(qbits == 160)
+      return (pbits == 512 || pbits == 768 || pbits == 1024);
+
+   if(qbits == 224)
+      return (pbits == 2048);
+
+   if(qbits == 256)
+      return (pbits == 2048 || pbits == 3072);
+
+   return false;
+   }
+
+}
+
+/*************************************************
+* Attempt DSA prime generation with given seed   *
+*************************************************/
+bool DL_Group::generate_dsa_primes(RandomNumberGenerator& rng,
+                                   BigInt& p, BigInt& q,
+                                   u32bit pbits, u32bit qbits,
+                                   const MemoryRegion<byte>& seed_c)
+   {
+   if(!fips186_3_valid_size(pbits, qbits))
+      throw Invalid_Argument(
+         "FIPS 186-3 does not allow DSA domain parameters of " +
+         to_string(pbits) + "/" + to_string(qbits) + " bits long");
+
+   if(qbits == 224)
+      throw Invalid_Argument(
+         "DSA parameter generation with a q of 224 bits not supported");
+
+   if(seed_c.size() * 8 < qbits)
+      throw Invalid_Argument(
+         "Generating a DSA parameter set with a " + to_string(qbits) +
+         "long q requires a seed at least as many bits long");
+
+   std::auto_ptr<HashFunction> hash(get_hash("SHA-" + to_string(qbits)));
+
+   const u32bit HASH_SIZE = hash->OUTPUT_LENGTH;
+
+   class Seed
+      {
+      public:
+         Seed(const MemoryRegion<byte>& s) : seed(s) {}
+
+         operator MemoryRegion<byte>& () { return seed; }
+
+         Seed& operator++()
+            {
+            for(u32bit j = seed.size(); j > 0; --j)
+               if(++seed[j-1])
+                  break;
+            return (*this);
+            }
+      private:
+         SecureVector<byte> seed;
+      };
+
+   Seed seed(seed_c);
+
+   q.binary_decode(hash->process(seed));
+   q.set_bit(qbits-1);
+   q.set_bit(0);
+
+   if(!is_prime(q, rng))
+      return false;
+
+   const u32bit n = (pbits-1) / (HASH_SIZE * 8),
+                b = (pbits-1) % (HASH_SIZE * 8);
+
+   BigInt X;
+   SecureVector<byte> V(HASH_SIZE * (n+1));
+
+   for(u32bit j = 0; j != 4096; ++j)
+      {
+      for(u32bit k = 0; k <= n; ++k)
+         {
+         ++seed;
+         hash->update(seed);
+         hash->final(V + HASH_SIZE * (n-k));
+         }
+
+      X.binary_decode(V + (HASH_SIZE - 1 - b/8),
+                      V.size() - (HASH_SIZE - 1 - b/8));
+      X.set_bit(pbits-1);
+
+      p = X - (X % (2*q) - 1);
+
+      if(p.bits() == pbits && is_prime(p, rng))
+         return true;
+      }
+   return false;
+   }
+
+/*************************************************
+* Generate DSA Primes                            *
+*************************************************/
+SecureVector<byte> DL_Group::generate_dsa_primes(RandomNumberGenerator& rng,
+                                                 BigInt& p, BigInt& q,
+                                                 u32bit pbits, u32bit qbits)
+   {
+   SecureVector<byte> seed(qbits/8);
+
+   while(true)
+      {
+      rng.randomize(seed, seed.size());
+
+      if(generate_dsa_primes(rng, p, q, pbits, qbits, seed))
+         return seed;
+      }
+   }
+
+}