Some small changes to GFpElement, including accepting u64bit instead

of u32bit to the operator* and operator*=

Instead of passing the n_dash array to inner_montg_mult_sos, which only
uses the first word, just pass the word directly.

1 files changed, 25 insertions, 27 deletions

diff --git a/src/math/gfpmath/gfp_element.cpp b/src/math/gfpmath/gfp_element.cpp
index d03439f0d..47b5429b3 100644
--- a/src/math/gfpmath/gfp_element.cpp
+++ b/src/math/gfpmath/gfp_element.cpp
@@ -1,13 +1,14 @@
 /******************************************************
- * Arithmetic for prime fields GF(p) (source file)    *
- *                                                    *
- * (C) 2007 Martin Doering                            *
- *          [email protected]    *
- *          Christoph Ludwig                          *
- *          [email protected]                        *
- *          Falko Strenzke                            *
- *          [email protected]                    *
- ******************************************************/
+* Arithmetic for prime fields GF(p)                   *
+*                                                     *
+* (C) 2007 Martin Doering                             *
+*          [email protected]     *
+*          Christoph Ludwig                           *
+*          [email protected]                         *
+*          Falko Strenzke                             *
+*          [email protected]                     *
+*     2008 Jack Lloyd                                 *
+******************************************************/
 
 #include <botan/gfp_element.h>
 #include <botan/numthry.h>
@@ -21,7 +22,7 @@ namespace Botan {
 
 namespace {
 
-void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, const word* n, const word* n_dash, u32bit s)
+void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, const word* n, const word n_dash, u32bit s)
    {
    SecureVector<word> t;
    t.grow_to(2*s+1);
@@ -33,10 +34,6 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c
       word S = 0;
       for (u32bit j=0; j<s; j++)
          {
-         // we use:
-         // word word_madd3(word a, word b, word c, word d, word* carry)
-         // returns a * b + c + d and resets the carry (not using it as input)
-
          S = word_madd3(a_bar[j], b_bar[i], t[i+j], &C);
          t[i+j] = S;
          }
@@ -51,7 +48,7 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c
 
       word C = 0;
       word zero = 0;
-      word m = word_madd2(t[i], n_dash[0], &zero);
+      word m = word_madd2(t[i], n_dash, &zero);
 
       for (u32bit j=0; j<s; j++)
          {
@@ -115,18 +112,19 @@ void montg_mult(BigInt& result, BigInt& a_bar, BigInt& b_bar, const BigInt& m, c
    if(a_bar.is_zero() || b_bar.is_zero())
       result = 0;
 
-#if 0
    u32bit s = m.sig_words();
    a_bar.grow_to(s);
    b_bar.grow_to(s);
    result.grow_to(s);
 
-   inner_montg_mult_sos(result.get_reg(), a_bar.data(), b_bar.data(), m.data(), m_dash.data(), s);
-#else
-   result = a_bar * b_bar * m_dash;
-   if(result >= m)
-      result -= m;
-#endif
+   inner_montg_mult_sos(result.get_reg(), a_bar.data(), b_bar.data(), m.data(), m_dash.data()[0], s);
+   /*
+   std::cout << "result = " << result << "\n"
+             << "a_bar = " << a_bar << "\n"
+             << "b_bar = " << b_bar << "\n"
+             << "m = " << m << "\n"
+             << "m_dash = " << m_dash.data()[0] << "\n";
+   */
    }
 
 /**
@@ -135,6 +133,8 @@ void montg_mult(BigInt& result, BigInt& a_bar, BigInt& b_bar, const BigInt& m, c
 */
 BigInt montgm_calc_r_oddmod(const BigInt& prime)
    {
+   assert(prime.is_odd());
+
    u32bit n = prime.sig_words();
    BigInt result(1);
    result <<= n*BOTAN_MP_WORD_BITS;
@@ -196,7 +196,6 @@ GFpElement::GFpElement(const GFpElement& other)
    : m_value(other.m_value),
      m_use_montgm(other.m_use_montgm),
      m_is_trf(other.m_is_trf)
-
    {
    //creates an independent copy
    assert((other.m_is_trf && other.m_use_montgm) || !other.m_is_trf);
@@ -246,7 +245,6 @@ void GFpElement::ensure_montgm_precomp() const
       assert(!mp_mod->m_r_inv.is_zero());
       assert(!mp_mod->m_p_dash.is_zero());
       }
-
    }
 
 void GFpElement::set_shrd_mod(std::tr1::shared_ptr<GFpModulus> const p_mod)
@@ -484,7 +482,7 @@ GFpElement& GFpElement::operator-=(const GFpElement& rhs)
    return *this;
    }
 
-GFpElement& GFpElement::operator*= (u32bit rhs)
+GFpElement& GFpElement::operator*= (u64bit rhs)
    {
    workspace = m_value;
    workspace *= rhs;
@@ -663,14 +661,14 @@ GFpElement operator*(const GFpElement& lhs, const GFpElement& rhs)
    return result;
    }
 
-GFpElement operator*(const GFpElement& lhs, u32bit rhs)
+GFpElement operator*(const GFpElement& lhs, u64bit rhs)
    {
    GFpElement result(lhs);
    result *= rhs;
    return result;
    }
 
-GFpElement operator*(u32bit lhs, const GFpElement& rhs)
+GFpElement operator*(u64bit lhs, const GFpElement& rhs)
    {
    return rhs*lhs;
    }