diff options
Diffstat (limited to 'src/lib/math')
| -rw-r--r-- | src/lib/math/numbertheory/monty_exp.cpp | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/src/lib/math/numbertheory/monty_exp.cpp b/src/lib/math/numbertheory/monty_exp.cpp index 62ba8fcc5..f067f33f8 100644 --- a/src/lib/math/numbertheory/monty_exp.cpp +++ b/src/lib/math/numbertheory/monty_exp.cpp @@ -76,22 +76,26 @@ void const_time_lookup(secure_vector<word>& output, const std::vector<Montgomery_Int>& g, size_t nibble) { + BOTAN_ASSERT_NOMSG(g.size() % 2 == 0); // actually a power of 2 + const size_t words = output.size(); clear_mem(output.data(), output.size()); - for(size_t i = 0; i != g.size(); ++i) + for(size_t i = 0; i != g.size(); i += 2) { - const secure_vector<word>& vec = g[i].repr().get_word_vector(); + const secure_vector<word>& vec_0 = g[i ].repr().get_word_vector(); + const secure_vector<word>& vec_1 = g[i+1].repr().get_word_vector(); - BOTAN_ASSERT(vec.size() >= words, - "Word size as expected in const_time_lookup"); + BOTAN_ASSERT_NOMSG(vec_0.size() >= words && vec_1.size() >= words); - const auto mask = CT::Mask<word>::is_equal(i, nibble); + const auto mask_0 = CT::Mask<word>::is_equal(nibble, i); + const auto mask_1 = CT::Mask<word>::is_equal(nibble, i+1); for(size_t w = 0; w != words; ++w) { - output[w] |= mask.if_set_return(vec[w]); + output[w] |= mask_0.if_set_return(vec_0[w]); + output[w] |= mask_1.if_set_return(vec_1[w]); } } } |