diff options
Diffstat (limited to 'src/lib')
| -rw-r--r-- | src/lib/pubkey/ec_group/point_mul.cpp | 33 | ||||
| -rw-r--r-- | src/lib/pubkey/ec_group/point_mul.h | 1 |
2 files changed, 24 insertions, 10 deletions
diff --git a/src/lib/pubkey/ec_group/point_mul.cpp b/src/lib/pubkey/ec_group/point_mul.cpp index 7b36d3fed..487fb9884 100644 --- a/src/lib/pubkey/ec_group/point_mul.cpp +++ b/src/lib/pubkey/ec_group/point_mul.cpp @@ -43,14 +43,24 @@ PointGFp_Base_Point_Precompute::PointGFp_Base_Point_Precompute(const PointGFp& b * the size of the prime modulus. In all cases they are at most 1 bit * longer. The +1 compensates for this. */ - const size_t T_bits = p_bits + PointGFp_SCALAR_BLINDING_BITS + 1; + m_T_bits = round_up(p_bits + PointGFp_SCALAR_BLINDING_BITS + 1, 2); - m_T.push_back(base); + m_T.resize(3*m_T_bits); - for(size_t i = 1; i != T_bits; ++i) + m_T[0] = base; + m_T[1] = m_T[0]; + m_T[1].mult2(ws); + m_T[2] = m_T[1]; + m_T[2].add(m_T[0], ws); + + for(size_t i = 1; i != m_T_bits; ++i) { - m_T.push_back(m_T[i-1]); - m_T[i].mult2(ws); + m_T[3*i+0] = m_T[3*i - 2]; + m_T[3*i+0].mult2(ws); + m_T[3*i+1] = m_T[3*i+0]; + m_T[3*i+1].mult2(ws); + m_T[3*i+2] = m_T[3*i+1]; + m_T[3*i+2].add(m_T[3*i+0], ws); } PointGFp::force_all_affine(m_T, ws[0].get_word_vector()); @@ -70,7 +80,7 @@ PointGFp PointGFp_Base_Point_Precompute::mul(const BigInt& k, const size_t scalar_bits = scalar.bits(); - BOTAN_ASSERT(scalar_bits <= m_T.size(), + BOTAN_ASSERT(scalar_bits <= m_T_bits, "Precomputed sufficient values for scalar mult"); PointGFp R = m_T[0].zero(); @@ -78,16 +88,19 @@ PointGFp PointGFp_Base_Point_Precompute::mul(const BigInt& k, if(ws.size() < PointGFp::WORKSPACE_SIZE) ws.resize(PointGFp::WORKSPACE_SIZE); - for(size_t i = 0; i != scalar_bits; ++i) + size_t windows = round_up(scalar_bits, 2) / 2; + + for(size_t i = 0; i != windows; ++i) { - //if(i % 4 == 3) if(i == 4) { R.randomize_repr(rng, ws[0].get_word_vector()); } - if(scalar.get_bit(i)) - R.add_affine(m_T[i], ws); + const uint32_t w = scalar.get_substring(2*i, 2); + + if(w > 0) + R.add_affine(m_T[3*i + w - 1], ws); } BOTAN_DEBUG_ASSERT(R.on_the_curve()); diff --git a/src/lib/pubkey/ec_group/point_mul.h b/src/lib/pubkey/ec_group/point_mul.h index 97fd326a2..b6e9da3b9 100644 --- a/src/lib/pubkey/ec_group/point_mul.h +++ b/src/lib/pubkey/ec_group/point_mul.h @@ -23,6 +23,7 @@ class PointGFp_Base_Point_Precompute const BigInt& group_order, std::vector<BigInt>& ws) const; private: + size_t m_T_bits; std::vector<PointGFp> m_T; }; |