1 files changed, 90 insertions, 0 deletions
diff --git a/src/libs/3rdparty/botan/src/lib/math/numbertheory/reducer.cpp b/src/libs/3rdparty/botan/src/lib/math/numbertheory/reducer.cpp
new file mode 100644
index 0000000000..98cf698ed7
--- /dev/null
+++ b/src/libs/3rdparty/botan/src/lib/math/numbertheory/reducer.cpp
@@ -0,0 +1,90 @@
+/*
+* Modular Reducer
+* (C) 1999-2011,2018 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/reducer.h>
+#include <botan/internal/ct_utils.h>
+
+namespace Botan {
+
+/*
+* Modular_Reducer Constructor
+*/
+Modular_Reducer::Modular_Reducer(const BigInt& mod)
+   {
+   if(mod < 0)
+      throw Invalid_Argument("Modular_Reducer: modulus must be positive");
+
+   // Left uninitialized if mod == 0
+   m_mod_words = 0;
+
+   if(mod > 0)
+      {
+      m_modulus = mod;
+      m_mod_words = m_modulus.sig_words();
+
+      m_modulus_2 = Botan::square(m_modulus);
+
+      m_mu = BigInt::power_of_2(2 * BOTAN_MP_WORD_BITS * m_mod_words) / m_modulus;
+      }
+   }
+
+/*
+* Barrett Reduction
+*/
+BigInt Modular_Reducer::reduce(const BigInt& x) const
+   {
+   if(m_mod_words == 0)
+      throw Invalid_State("Modular_Reducer: Never initalized");
+
+   const size_t x_sw = x.sig_words();
+
+   if(x_sw >= (2*m_mod_words - 1) && x.cmp(m_modulus_2, false) >= 0)
+      {
+      // too big, fall back to normal division
+      return (x % m_modulus);
+      }
+
+   secure_vector<word> ws;
+
+   BigInt t1 = x;
+   t1.set_sign(BigInt::Positive);
+   t1 >>= (BOTAN_MP_WORD_BITS * (m_mod_words - 1));
+
+   t1.mul(m_mu, ws);
+   t1 >>= (BOTAN_MP_WORD_BITS * (m_mod_words + 1));
+
+   // TODO add masked mul to avoid computing high bits
+   t1.mul(m_modulus, ws);
+   t1.mask_bits(BOTAN_MP_WORD_BITS * (m_mod_words + 1));
+
+   t1.rev_sub(x.data(), std::min(x_sw, m_mod_words + 1), ws);
+
+   /*
+   * If t1 < 0 then we must add b^(k+1) where b = 2^w. To avoid a
+   * side channel perform the addition unconditionally, with ws set
+   * to either b^(k+1) or else 0.
+   */
+   const word t1_neg = t1.is_negative();
+
+   if(ws.size() < m_mod_words + 2)
+      ws.resize(m_mod_words + 2);
+   clear_mem(ws.data(), ws.size());
+   ws[m_mod_words + 1] = t1_neg;
+
+   t1.add(ws.data(), m_mod_words + 2, BigInt::Positive);
+
+   t1.reduce_below(m_modulus, ws);
+
+   if(x.is_negative() && t1.is_nonzero())
+      {
+      t1.rev_sub(m_modulus.data(), m_modulus.size(), ws);
+      }
+
+   return t1;
+   }
+
+}