1 files changed, 68 insertions, 0 deletions
diff --git a/botan/src/utils/util.cpp b/botan/src/utils/util.cpp
new file mode 100644
index 0000000..84dfd1a
--- /dev/null
+++ b/botan/src/utils/util.cpp
@@ -0,0 +1,68 @@
+/*
+* Utility Functions
+* (C) 1999-2007 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/util.h>
+#include <algorithm>
+#include <cmath>
+
+namespace Botan {
+
+/*
+* Round up n to multiple of align_to
+*/
+u32bit round_up(u32bit n, u32bit align_to)
+   {
+   if(n % align_to || n == 0)
+      n += align_to - (n % align_to);
+   return n;
+   }
+
+/*
+* Round down n to multiple of align_to
+*/
+u32bit round_down(u32bit n, u32bit align_to)
+   {
+   return (n - (n % align_to));
+   }
+
+/*
+* Choose the exponent size for a DL group
+*/
+u32bit dl_work_factor(u32bit bits)
+   {
+#if 0
+   /*
+   These values were taken from RFC 3526
+   */
+   if(bits <= 1536)
+      return 90;
+   else if(bits <= 2048)
+      return 110;
+   else if(bits <= 3072)
+      return 130;
+   else if(bits <= 4096)
+      return 150;
+   else if(bits <= 6144)
+      return 170;
+   else if(bits <= 8192)
+      return 190;
+   return 256;
+#else
+   const u32bit MIN_ESTIMATE = 64;
+
+   const double log_x = bits / 1.44;
+
+   const double strength =
+      2.76 * std::pow(log_x, 1.0/3.0) * std::pow(std::log(log_x), 2.0/3.0);
+
+   if(strength > MIN_ESTIMATE)
+      return static_cast<u32bit>(strength);
+   return MIN_ESTIMATE;
+#endif
+   }
+
+}