1 files changed, 59 insertions, 0 deletions
diff --git a/src/math/bigint/big_rand.cpp b/src/math/bigint/big_rand.cpp
new file mode 100644
index 000000000..055873642
--- /dev/null
+++ b/src/math/bigint/big_rand.cpp
@@ -0,0 +1,59 @@
+/*************************************************
+* BigInt Random Generation Source File           *
+* (C) 1999-2007 Jack Lloyd                       *
+*************************************************/
+
+#include <botan/bigint.h>
+#include <botan/parsing.h>
+
+namespace Botan {
+
+/*************************************************
+* Construct a BigInt of a specific form          *
+*************************************************/
+BigInt::BigInt(NumberType type, u32bit bits)
+   {
+   set_sign(Positive);
+
+   if(type == Power2)
+      set_bit(bits);
+   else
+      throw Invalid_Argument("BigInt(NumberType): Unknown type");
+   }
+
+/*************************************************
+* Randomize this number                          *
+*************************************************/
+void BigInt::randomize(RandomNumberGenerator& rng,
+                       u32bit bitsize)
+   {
+   set_sign(Positive);
+
+   if(bitsize == 0)
+      clear();
+   else
+      {
+      SecureVector<byte> array((bitsize + 7) / 8);
+      rng.randomize(array, array.size());
+      if(bitsize % 8)
+         array[0] &= 0xFF >> (8 - (bitsize % 8));
+      array[0] |= 0x80 >> ((bitsize % 8) ? (8 - bitsize % 8) : 0);
+      binary_decode(array, array.size());
+      }
+   }
+
+/*************************************************
+* Generate a random integer within given range   *
+*************************************************/
+BigInt BigInt::random_integer(RandomNumberGenerator& rng,
+                              const BigInt& min, const BigInt& max)
+   {
+   BigInt range = max - min;
+
+   if(range <= 0)
+      throw Invalid_Argument("random_integer: invalid min/max values");
+
+   return (min + (BigInt(rng, range.bits() + 2) % range));
+   }
+
+}