diff options
Diffstat (limited to 'src/crypto/bigint.c')
| -rw-r--r-- | src/crypto/bigint.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/src/crypto/bigint.c b/src/crypto/bigint.c index ac9670ef..656f979e 100644 --- a/src/crypto/bigint.c +++ b/src/crypto/bigint.c @@ -51,6 +51,31 @@ static struct profiler bigint_mod_multiply_subtract_profiler __profiler = { .name = "bigint_mod_multiply.subtract" }; /** + * Conditionally swap big integers (in constant time) + * + * @v first0 Element 0 of big integer to be conditionally swapped + * @v second0 Element 0 of big integer to be conditionally swapped + * @v size Number of elements in big integers + * @v swap Swap first and second big integers + */ +void bigint_swap_raw ( bigint_element_t *first0, bigint_element_t *second0, + unsigned int size, int swap ) { + bigint_element_t mask; + bigint_element_t xor; + unsigned int i; + + /* Construct mask */ + mask = ( ( bigint_element_t ) ( ! swap ) - 1 ); + + /* Conditionally swap elements */ + for ( i = 0 ; i < size ; i++ ) { + xor = ( mask & ( first0[i] ^ second0[i] ) ); + first0[i] ^= xor; + second0[i] ^= xor; + } +} + +/** * Perform modular multiplication of big integers * * @v multiplicand0 Element 0 of big integer to be multiplied |