1 files changed, 51 insertions, 0 deletions
diff --git a/src/pubkey/workfactor.cpp b/src/pubkey/workfactor.cpp
new file mode 100644
index 000000000..e40b7919c
--- /dev/null
+++ b/src/pubkey/workfactor.cpp
@@ -0,0 +1,51 @@
+/*
+* Public Key Work Factor Functions
+* (C) 1999-2007 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/workfactor.h>
+#include <algorithm>
+#include <cmath>
+
+namespace Botan {
+
+/*
+* 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
+   }
+
+
+}