diff options
Diffstat (limited to 'src/math/gfpmath/gfp_element.cpp')
| -rw-r--r-- | src/math/gfpmath/gfp_element.cpp | 50 |
1 files changed, 29 insertions, 21 deletions
diff --git a/src/math/gfpmath/gfp_element.cpp b/src/math/gfpmath/gfp_element.cpp index c5dd58c91..d03439f0d 100644 --- a/src/math/gfpmath/gfp_element.cpp +++ b/src/math/gfpmath/gfp_element.cpp @@ -1,7 +1,7 @@ /****************************************************** * Arithmetic for prime fields GF(p) (source file) * * * - * (C) 2007 Martin Döring * + * (C) 2007 Martin Doering * * Christoph Ludwig * @@ -26,6 +26,7 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c SecureVector<word> t; t.grow_to(2*s+1); + // t = a_bar * b_bar for (u32bit i=0; i<s; i++) { word C = 0; @@ -42,15 +43,15 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c t[i+s] = C; } - + // ??? for (u32bit i=0; i<s; i++) { // word word_madd2(word a, word b, word c, word* carry) // returns a * b + c, resets the carry word C = 0; - word unused_carry = 0; - word m = word_madd2(t[i], n_dash[0], &unused_carry); + word zero = 0; + word m = word_madd2(t[i], n_dash[0], &zero); for (u32bit j=0; j<s; j++) { @@ -69,6 +70,8 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c cnt++; } } + + // u = t SecureVector<word> u; u.grow_to(s+1); for (u32bit j=0; j<s+1; j++) @@ -76,6 +79,7 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c u[j] = t[j+s]; } + // t = u - n word B = 0; word D = 0; for (u32bit i=0; i<s; i++) @@ -85,6 +89,8 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c } D = word_sub(u[s], 0, &B); t[s] = D; + + // if t >= 0 (B == 0 -> no borrow), return t if(B == 0) { for (u32bit i=0; i<s; i++) @@ -92,7 +98,7 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c result[i] = t[i]; } } - else + else // else return u { for (u32bit i=0; i<s; i++) { @@ -104,21 +110,23 @@ void inner_montg_mult_sos(word result[], const word* a_bar, const word* b_bar, c void montg_mult(BigInt& result, BigInt& a_bar, BigInt& b_bar, const BigInt& m, const BigInt& m_dash, const BigInt) { if(m.is_zero() || m_dash.is_zero()) - { throw Invalid_Argument("montg_mult(): neither modulus nor m_dash may be zero (and one of them was)"); - } + 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 } /** @@ -131,7 +139,6 @@ BigInt montgm_calc_r_oddmod(const BigInt& prime) BigInt result(1); result <<= n*BOTAN_MP_WORD_BITS; return result; - } /** @@ -143,6 +150,7 @@ BigInt montgm_calc_m_dash(const BigInt& r, const BigInt& m, const BigInt& r_inv) BigInt result = ((r * r_inv) - BigInt(1))/m; return result; } + BigInt montg_trf_to_mres(const BigInt& ord_res, const BigInt& r, const BigInt& m) { BigInt result(ord_res); @@ -150,6 +158,7 @@ BigInt montg_trf_to_mres(const BigInt& ord_res, const BigInt& r, const BigInt& m result %= m; return result; } + BigInt montg_trf_to_ordres(const BigInt& m_res, const BigInt& m, const BigInt& r_inv) { BigInt result(m_res); @@ -158,7 +167,6 @@ BigInt montg_trf_to_ordres(const BigInt& m_res, const BigInt& m, const BigInt& r return result; } - } GFpElement::GFpElement(const BigInt& p, const BigInt& value, bool use_montgm) @@ -200,6 +208,7 @@ void GFpElement::turn_on_sp_red_mul() const ensure_montgm_precomp(); m_use_montgm = true; } + void GFpElement::turn_off_sp_red_mul() const { if(m_is_trf) @@ -210,6 +219,7 @@ void GFpElement::turn_off_sp_red_mul() const } m_use_montgm = false; } + void GFpElement::ensure_montgm_precomp() const { if((!mp_mod->m_r.is_zero()) && (!mp_mod->m_r_inv.is_zero()) && (!mp_mod->m_p_dash.is_zero())) @@ -243,6 +253,7 @@ void GFpElement::set_shrd_mod(std::tr1::shared_ptr<GFpModulus> const p_mod) { mp_mod = p_mod; } + void GFpElement::trf_to_mres() const { if(!m_use_montgm) @@ -255,18 +266,19 @@ void GFpElement::trf_to_mres() const m_value = montg_trf_to_mres(m_value, mp_mod->m_r, mp_mod->m_p); m_is_trf = true; } + void GFpElement::trf_to_ordres() const { assert(m_is_trf == true); m_value = montg_trf_to_ordres(m_value, mp_mod->m_p, mp_mod->m_r_inv); m_is_trf = false; } + bool GFpElement::align_operands_res(const GFpElement& lhs, const GFpElement& rhs) //static { assert(lhs.mp_mod->m_p == rhs.mp_mod->m_p); if(lhs.m_use_montgm && rhs.m_use_montgm) { - assert(rhs.mp_mod->m_p_dash == lhs.mp_mod->m_p_dash); assert(rhs.mp_mod->m_r == lhs.mp_mod->m_r); assert(rhs.mp_mod->m_r_inv == lhs.mp_mod->m_r_inv); @@ -310,7 +322,6 @@ bool GFpElement::align_operands_res(const GFpElement& lhs, const GFpElement& rhs return false; } assert(false); - } bool GFpElement::is_trf_to_mres() const @@ -447,9 +458,7 @@ GFpElement& GFpElement::operator+=(const GFpElement& rhs) workspace = m_value; workspace += rhs.m_value; if(workspace >= mp_mod->m_p) - { workspace -= mp_mod->m_p; - } m_value = workspace; assert(m_value < mp_mod->m_p); @@ -467,9 +476,7 @@ GFpElement& GFpElement::operator-=(const GFpElement& rhs) workspace -= rhs.m_value; if(workspace.is_negative()) - { workspace += mp_mod->m_p; - } m_value = workspace; assert(m_value < mp_mod->m_p); @@ -491,7 +498,7 @@ GFpElement& GFpElement::operator*=(const GFpElement& rhs) assert(rhs.mp_mod->m_p == mp_mod->m_p); // here, we do not use align_operands_res() for one simple reason: // we want to enforce the transformation to an m-residue, otherwise it would - // never happen + // never happen if(m_use_montgm && rhs.m_use_montgm) { assert(rhs.mp_mod->m_p == mp_mod->m_p); // is montgm. mult is on, then precomps must be there @@ -520,6 +527,7 @@ GFpElement& GFpElement::operator*=(const GFpElement& rhs) assert(rhs.m_use_montgm); rhs.trf_to_ordres(); } + workspace = m_value; workspace *= rhs.m_value; workspace %= mp_mod->m_p; @@ -592,7 +600,7 @@ void GFpElement::swap(GFpElement& other) std::ostream& operator<<(std::ostream& output, const GFpElement& elem) { - return output << elem.get_p() << "," << elem.get_value(); + return output << '(' << elem.get_value() << "," << elem.get_p() << ')'; } bool operator==(const GFpElement& lhs, const GFpElement& rhs) |