diff options
Diffstat (limited to 'pyecsca/codegen/mult')
| -rw-r--r-- | pyecsca/codegen/mult/double_and_add.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/pyecsca/codegen/mult/double_and_add.c b/pyecsca/codegen/mult/double_and_add.c index 91ad6e3..1fd3c9e 100644 --- a/pyecsca/codegen/mult/double_and_add.c +++ b/pyecsca/codegen/mult/double_and_add.c @@ -1,5 +1,18 @@ #include "mult.h" void scalar_mult(bn_t *scalar, point_t *point, curve_t *curve, point_t *out) { - + point_t *q = point_copy(point); + point_t *r = point_copy(curve->neutral); + + int nbits = bn_bit_length(curve->n); + for (int i = nbits; i >= 0; i--) { + point_dbl(r, curve, r); + if (bn_get_bit(scalar, i) == 1) { + point_add(q, r, curve, r); + } + } + point_scl(r, curve, r); + point_set(r, out); + point_free(q); + point_free(r); }
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