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[crypto] Eliminate temporary working space for bigint_mod_invert()

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With a slight modification to the algorithm to ignore bits of the
residue that can never contribute to the result, it is possible to
reuse the as-yet uncalculated portions of the inverse to hold the
residue.  This removes the requirement for additional temporary
working space.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2024-11-27 12:51:04 +00:00
parent 9cbf5c4f86
commit 7c2e68cc87
3 changed files with 65 additions and 46 deletions
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24
src/include/ipxe/bigint.h
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@@ -242,30 +242,17 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
} while ( 0 )
/**
* Compute inverse of odd big integer modulo its own size
* Compute inverse of odd big integer modulo any power of two
*
* @v invertend Odd big integer to be inverted
* @v inverse Big integer to hold result
* @v tmp Temporary working space
*/
#define bigint_mod_invert( invertend, inverse, tmp ) do { \
unsigned int size = bigint_size (invertend); \
#define bigint_mod_invert( invertend, inverse ) do { \
unsigned int size = bigint_size ( invertend ); \
bigint_mod_invert_raw ( (invertend)->element, \
(inverse)->element, size, tmp ); \
(inverse)->element, size ); \
} while ( 0 )
/**
* Calculate temporary working space required for modular inversion
*
* @v invertend Odd big integer to be inverted
* @ret len Length of temporary working space
*/
#define bigint_mod_invert_tmp_len( invertend ) ( { \
unsigned int size = bigint_size (invertend); \
sizeof ( struct { \
bigint_t ( size ) temp_residue; \
} ); } )
/**
* Perform modular multiplication of big integers
*
@@ -408,8 +395,7 @@ void bigint_multiply_raw ( const bigint_element_t *multiplicand0,
void bigint_reduce_raw ( bigint_element_t *modulus0, bigint_element_t *value0,
unsigned int size );
void bigint_mod_invert_raw ( const bigint_element_t *invertend0,
bigint_element_t *inverse0,
unsigned int size, void *tmp );
bigint_element_t *inverse0, unsigned int size );
void bigint_mod_multiply_raw ( const bigint_element_t *multiplicand0,
const bigint_element_t *multiplier0,
const bigint_element_t *modulus0,