diff options
Diffstat (limited to 'src/math/numbertheory/point_gfp.cpp')
| -rw-r--r-- | src/math/numbertheory/point_gfp.cpp | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/src/math/numbertheory/point_gfp.cpp b/src/math/numbertheory/point_gfp.cpp index 6cc13d648..fd7f828c7 100644 --- a/src/math/numbertheory/point_gfp.cpp +++ b/src/math/numbertheory/point_gfp.cpp @@ -13,6 +13,8 @@ #include <botan/mp_asmi.h> #include <botan/mp_core.h> +#include <stdio.h> + namespace Botan { PointGFp::PointGFp(const CurveGFp& curve) : @@ -170,10 +172,30 @@ PointGFp& PointGFp::operator*=(const BigInt& scalar) if(scalar.is_negative()) P.negate(); - for(int i = scalar.bits() - 1; i >= 0; --i) + u32bit scalar_bits = scalar.bits(); + + PointGFp P2 = P * 2; + PointGFp P3 = P2 + P; + + for(u32bit i = 0; i < scalar_bits - 1; i += 2) + { + u32bit twobits = scalar.get_substring(scalar_bits - i - 2, 2); + + H.mult2(); + H.mult2(); + + if(twobits == 3) + H += P3; + else if(twobits == 2) + H += P2; + else if(twobits == 1) + H += P; + } + + if(scalar_bits % 2) { H.mult2(); - if(scalar.get_bit(i)) + if(scalar.get_bit(0)) H += P; } |