1 files changed, 54 insertions, 0 deletions
diff --git a/lib/engine/openssl/bn_powm.cpp b/lib/engine/openssl/bn_powm.cpp
new file mode 100644
index 000000000..ac06fbe77
--- /dev/null
+++ b/lib/engine/openssl/bn_powm.cpp
@@ -0,0 +1,54 @@
+/*
+* OpenSSL Modular Exponentiation
+* (C) 1999-2007 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/internal/openssl_engine.h>
+#include <botan/internal/bn_wrap.h>
+
+namespace Botan {
+
+namespace {
+
+/*
+* OpenSSL Modular Exponentiator
+*/
+class OpenSSL_Modular_Exponentiator : public Modular_Exponentiator
+   {
+   public:
+      void set_base(const BigInt& b) { base = b; }
+      void set_exponent(const BigInt& e) { exp = e; }
+      BigInt execute() const;
+      Modular_Exponentiator* copy() const
+         { return new OpenSSL_Modular_Exponentiator(*this); }
+
+      OpenSSL_Modular_Exponentiator(const BigInt& n) : mod(n) {}
+   private:
+      OSSL_BN base, exp, mod;
+      OSSL_BN_CTX ctx;
+   };
+
+/*
+* Compute the result
+*/
+BigInt OpenSSL_Modular_Exponentiator::execute() const
+   {
+   OSSL_BN r;
+   BN_mod_exp(r.ptr(), base.ptr(), exp.ptr(), mod.ptr(), ctx.ptr());
+   return r.to_bigint();
+   }
+
+}
+
+/*
+* Return the OpenSSL-based modular exponentiator
+*/
+Modular_Exponentiator* OpenSSL_Engine::mod_exp(const BigInt& n,
+                                               Power_Mod::Usage_Hints) const
+   {
+   return new OpenSSL_Modular_Exponentiator(n);
+   }
+
+}