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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/tests/bigint_test.c
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@@ -197,13 +197,13 @@ void bigint_reduce_sample ( bigint_element_t *modulus0,
void bigint_mod_invert_sample ( const bigint_element_t *invertend0,
bigint_element_t *inverse0,
unsigned int size, void *tmp ) {
unsigned int size ) {
const bigint_t ( size ) __attribute__ (( may_alias ))
*invertend = ( ( const void * ) invertend0 );
bigint_t ( size ) __attribute__ (( may_alias ))
*inverse = ( ( void * ) inverse0 );
bigint_mod_invert ( invertend, inverse, tmp );
bigint_mod_invert ( invertend, inverse );
}
void bigint_mod_multiply_sample ( const bigint_element_t *multiplicand0,
@@ -600,8 +600,6 @@ void bigint_mod_exp_sample ( const bigint_element_t *base0,
bigint_required_size ( sizeof ( invertend_raw ) ); \
bigint_t ( size ) invertend_temp; \
bigint_t ( size ) inverse_temp; \
size_t tmp_len = bigint_mod_invert_tmp_len ( &invertend_temp ); \
uint8_t tmp[tmp_len]; \
{} /* Fix emacs alignment */ \
\
assert ( bigint_size ( &invertend_temp ) == \
@@ -610,7 +608,7 @@ void bigint_mod_exp_sample ( const bigint_element_t *base0,
sizeof ( invertend_raw ) ); \
DBG ( "Modular invert:\n" ); \
DBG_HDA ( 0, &invertend_temp, sizeof ( invertend_temp ) ); \
bigint_mod_invert ( &invertend_temp, &inverse_temp, tmp ); \
bigint_mod_invert ( &invertend_temp, &inverse_temp ); \
DBG_HDA ( 0, &inverse_temp, sizeof ( inverse_temp ) ); \
bigint_done ( &inverse_temp, inverse_raw, \
sizeof ( inverse_raw ) ); \
@@ -1827,6 +1825,10 @@ static void bigint_test_exec ( void ) {
0xff, 0xff ),
BIGINT ( 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff ) );
bigint_mod_invert_ok ( BIGINT ( 0xa4, 0xcb, 0xbc, 0xc9, 0x9f, 0x7a,
0x65, 0xbf ),
BIGINT ( 0xb9, 0xd5, 0xf4, 0x88, 0x0b, 0xf8,
0x8a, 0x3f ) );
bigint_mod_invert_ok ( BIGINT ( 0x95, 0x6a, 0xc5, 0xe7, 0x2e, 0x5b,
0x44, 0xed, 0xbf, 0x7e, 0xfe, 0x8d,
0xf4, 0x5a, 0x48, 0xc1 ),
@@ -1839,6 +1841,18 @@ static void bigint_test_exec ( void ) {
BIGINT ( 0xf2, 0x9c, 0x63, 0x29, 0xfa, 0xe4,
0xbf, 0x90, 0xa6, 0x9a, 0xec, 0xcf,
0x5f, 0xe2, 0x21, 0xcd ) );
bigint_mod_invert_ok ( BIGINT ( 0xb9, 0xbb, 0x7f, 0x9c, 0x7a, 0x32,
0x43, 0xed, 0x9d, 0xd4, 0x0d, 0x6f,
0x32, 0xfa, 0x4b, 0x62, 0x38, 0x3a,
0xbf, 0x4c, 0xbd, 0xa8, 0x47, 0xce,
0xa2, 0x30, 0x34, 0xe0, 0x2c, 0x09,
0x14, 0x89 ),
BIGINT ( 0xfc, 0x05, 0xc4, 0x2a, 0x90, 0x99,
0x82, 0xf8, 0x81, 0x1d, 0x87, 0xb8,
0xca, 0xe4, 0x95, 0xe2, 0xac, 0x18,
0xb3, 0xe1, 0x3e, 0xc6, 0x5a, 0x03,
0x51, 0x6f, 0xb7, 0xe3, 0xa5, 0xd6,
0xa1, 0xb9 ) );
bigint_mod_multiply_ok ( BIGINT ( 0x37 ),
BIGINT ( 0x67 ),
BIGINT ( 0x3f ),