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Merge pull request #6743 from minosgalanakis/bignum/implement_modular_negation

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Bignum: Implement fixed width modular negation
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Manuel Pégourié-Gonnard
2022-12-13 09:54:38 +01:00
committed by GitHub
parent 8a05c069a5 f3abea6641
commit 48232ed2c1
4 changed files with 94 additions and 0 deletions
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12
library/bignum_mod_raw.c
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@ -213,6 +213,18 @@ int mbedtls_mpi_mod_raw_from_mont_rep( mbedtls_mpi_uint *X,
mbedtls_free( T );
return( 0 );
}
void mbedtls_mpi_mod_raw_neg( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_mod_modulus *m )
{
mbedtls_mpi_core_sub( X, m->p, A, m->limbs );
/* If A=0 initially, then X=N now. Detect this by
* subtracting N and catching the carry. */
mbedtls_mpi_uint borrow = mbedtls_mpi_core_sub( X, X, m->p, m->limbs );
(void) mbedtls_mpi_core_add_if( X, m->p, m->limbs, (unsigned) borrow );
}
/* END MERGE SLOT 7 */
/* BEGIN MERGE SLOT 8 */