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Add low-level Montgomery conversion functions to bignum_core

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Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
This commit is contained in:
Tom Cosgrove 2022-12-13 10:45:19 +00:00
parent 28ff92cc3a
commit 786848b5c5
4 changed files with 173 additions and 19 deletions
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23
library/bignum_core.c
View File

@ -753,6 +753,29 @@ mbedtls_mpi_uint mbedtls_mpi_core_check_zero_ct( const mbedtls_mpi_uint *A,
return( bits );
}
void mbedtls_mpi_core_to_mont_rep( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *N,
size_t AN_limbs,
mbedtls_mpi_uint mm,
const mbedtls_mpi_uint *rr,
mbedtls_mpi_uint *T )
{
mbedtls_mpi_core_montmul( X, A, rr, AN_limbs, N, AN_limbs, mm, T );
}
void mbedtls_mpi_core_from_mont_rep( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *N,
size_t AN_limbs,
mbedtls_mpi_uint mm,
mbedtls_mpi_uint *T )
{
const mbedtls_mpi_uint Rinv = 1; /* 1/R in Mont. rep => 1 */
mbedtls_mpi_core_montmul( X, A, &Rinv, 1, N, AN_limbs, mm, T );
}
/* END MERGE SLOT 3 */
/* BEGIN MERGE SLOT 4 */

75
library/bignum_core.h
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@ -606,6 +606,81 @@ static inline size_t mbedtls_mpi_core_montmul_working_limbs( size_t AN_limbs )
return( 2 * AN_limbs + 1 );
}
/** Convert an MPI into Montgomery form.
*
* \p X may be aliased to \p A, but may not otherwise overlap it.
*
* \p X may not alias \p N (it is in canonical form, so must be stricly less
* than \p N). Nor may it alias or overlap \p rr (this is unlikely to be
* required in practice.)
*
* This function is a thin wrapper around `mbedtls_mpi_core_montmul()` that is
* an alternative to calling `mbedtls_mpi_mod_raw_to_mont_rep()` when we
* don't want to allocate memory.
*
* \param[out] X The result of the conversion.
* Must have the same number of limbs as \p A.
* \param[in] A The MPI to convert into Montgomery form.
* Must have the same number of limbs as the modulus.
* \param[in] N The address of the modulus, which gives the size of
* the base `R` = 2^(biL*m->limbs).
* \param[in] AN_limbs The number of limbs in \p X, \p A, \p N and \p rr.
* \param mm The Montgomery constant for \p N: -N^-1 mod 2^biL.
* This can be determined by calling
* `mbedtls_mpi_core_montmul_init()`.
* \param[in] rr The residue for `2^{2*n*biL} mod N`.
* \param[in,out] T Temporary storage of size at least
* `mbedtls_mpi_core_montmul_working_limbs(AN_limbs)`
* limbs.
* Its initial content is unused and
* its final content is indeterminate.
* It must not alias or otherwise overlap any of the
* other parameters.
*/
void mbedtls_mpi_core_to_mont_rep( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *N,
size_t AN_limbs,
mbedtls_mpi_uint mm,
const mbedtls_mpi_uint *rr,
mbedtls_mpi_uint *T );
/** Convert an MPI from Montgomery form.
*
* \p X may be aliased to \p A, but may not otherwise overlap it.
*
* \p X may not alias \p N (it is in canonical form, so must be stricly less
* than \p N).
*
* This function is a thin wrapper around `mbedtls_mpi_core_montmul()` that is
* an alternative to calling `mbedtls_mpi_mod_raw_from_mont_rep()` when we
* don't want to allocate memory.
*
* \param[out] X The result of the conversion.
* Must have the same number of limbs as \p A.
* \param[in] A The MPI to convert from Montgomery form.
* Must have the same number of limbs as the modulus.
* \param[in] N The address of the modulus, which gives the size of
* the base `R` = 2^(biL*m->limbs).
* \param[in] AN_limbs The number of limbs in \p X, \p A and \p N.
* \param mm The Montgomery constant for \p N: -N^-1 mod 2^biL.
* This can be determined by calling
* `mbedtls_mpi_core_montmul_init()`.
* \param[in,out] T Temporary storage of size at least
* `mbedtls_mpi_core_montmul_working_limbs(AN_limbs)`
* limbs.
* Its initial content is unused and
* its final content is indeterminate.
* It must not alias or otherwise overlap any of the
* other parameters.
*/
void mbedtls_mpi_core_from_mont_rep( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *N,
size_t AN_limbs,
mbedtls_mpi_uint mm,
mbedtls_mpi_uint *T );
/* END MERGE SLOT 3 */
/* BEGIN MERGE SLOT 4 */

8
library/bignum_mod_raw.c
View File

@ -188,8 +188,8 @@ int mbedtls_mpi_mod_raw_to_mont_rep( mbedtls_mpi_uint *X,
if( ( T = (mbedtls_mpi_uint *) mbedtls_calloc( t_limbs, ciL ) ) == NULL )
return( MBEDTLS_ERR_MPI_ALLOC_FAILED );
mbedtls_mpi_core_montmul( X, X, m->rep.mont.rr, m->limbs, m->p, m->limbs,
m->rep.mont.mm, T );
mbedtls_mpi_core_to_mont_rep( X, X, m->p, m->limbs,
m->rep.mont.mm, m->rep.mont.rr, T );
mbedtls_platform_zeroize( T, t_limbs * ciL );
mbedtls_free( T );
@ -199,15 +199,13 @@ int mbedtls_mpi_mod_raw_to_mont_rep( mbedtls_mpi_uint *X,
int mbedtls_mpi_mod_raw_from_mont_rep( mbedtls_mpi_uint *X,
const mbedtls_mpi_mod_modulus *m )
{
const mbedtls_mpi_uint one = 1;
const size_t t_limbs = mbedtls_mpi_core_montmul_working_limbs( m->limbs );
mbedtls_mpi_uint *T;
if( ( T = (mbedtls_mpi_uint *) mbedtls_calloc( t_limbs, ciL ) ) == NULL )
return( MBEDTLS_ERR_MPI_ALLOC_FAILED );
mbedtls_mpi_core_montmul( X, X, &one, 1, m->p, m->limbs,
m->rep.mont.mm, T );
mbedtls_mpi_core_from_mont_rep( X, X, m->p, m->limbs, m->rep.mont.mm, T );
mbedtls_platform_zeroize( T, t_limbs * ciL );
mbedtls_free( T );

86
tests/suites/test_suite_bignum_mod_raw.function
View File

@ -533,8 +533,10 @@ void mpi_mod_raw_to_mont_rep( char * input_N, char * input_A, char * input_X )
{
mbedtls_mpi_uint *N = NULL;
mbedtls_mpi_uint *A = NULL;
mbedtls_mpi_uint *R = NULL; /* for result of low-level conversion */
mbedtls_mpi_uint *X = NULL;
size_t n_limbs, a_limbs, x_limbs, x_bytes;
mbedtls_mpi_uint *T = NULL;
size_t n_limbs, a_limbs, x_limbs;
mbedtls_mpi_mod_modulus m;
mbedtls_mpi_mod_modulus_init( &m );
@ -543,23 +545,50 @@ void mpi_mod_raw_to_mont_rep( char * input_N, char * input_A, char * input_X )
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &N, &n_limbs, input_N ) );
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &A, &a_limbs, input_A ) );
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &X, &x_limbs, input_X ) );
x_bytes = x_limbs * sizeof(mbedtls_mpi_uint);
/* Test that input does not require more limbs than modulo */
TEST_LE_U(a_limbs, n_limbs);
/* Number to convert must have same number of limbs as modulus */
TEST_EQUAL(a_limbs, n_limbs);
/* Higher-level conversion is in-place, so expected result must have the
* same number of limbs too */
TEST_EQUAL(x_limbs, n_limbs);
size_t limbs = n_limbs;
size_t bytes = limbs * sizeof(mbedtls_mpi_uint);
TEST_EQUAL( 0, mbedtls_mpi_mod_modulus_setup( &m, N, n_limbs,
MBEDTLS_MPI_MOD_REP_MONTGOMERY ) );
MBEDTLS_MPI_MOD_REP_MONTGOMERY ) );
/* 1. Test low-level function first */
/* It has separate output, and requires temporary working storage */
size_t temp_limbs = mbedtls_mpi_core_montmul_working_limbs( limbs );
ASSERT_ALLOC( T, temp_limbs );
ASSERT_ALLOC( R, limbs );
mbedtls_mpi_core_to_mont_rep( R, A, N, n_limbs,
m.rep.mont.mm, m.rep.mont.rr, T );
/* Test that the low-level function gives the required value */
ASSERT_COMPARE( R, bytes, X, bytes );
/* Test when output is aliased to input */
memcpy( R, A, bytes );
mbedtls_mpi_core_to_mont_rep( R, R, N, n_limbs,
m.rep.mont.mm, m.rep.mont.rr, T );
ASSERT_COMPARE( R, bytes, X, bytes );
/* 2. Test higher-level cannonical to Montgomery conversion */
/* Convert from cannonical into Montgomery representation */
TEST_EQUAL(0, mbedtls_mpi_mod_raw_to_mont_rep( A, &m ) );
/* The result matches expected value */
ASSERT_COMPARE( A, x_bytes, X, x_bytes );
ASSERT_COMPARE( A, bytes, X, bytes );
exit:
mbedtls_mpi_mod_modulus_free( &m );
mbedtls_free( T );
mbedtls_free( N );
mbedtls_free( A );
mbedtls_free( R );
mbedtls_free( X );
}
/* END_CASE */
@ -569,8 +598,10 @@ void mpi_mod_raw_from_mont_rep( char * input_N, char * input_A, char * input_X )
{
mbedtls_mpi_uint *N = NULL;
mbedtls_mpi_uint *A = NULL;
mbedtls_mpi_uint *R = NULL; /* for result of low-level conversion */
mbedtls_mpi_uint *X = NULL;
size_t n_limbs, a_limbs, x_limbs, x_bytes;
mbedtls_mpi_uint *T = NULL;
size_t n_limbs, a_limbs, x_limbs;
mbedtls_mpi_mod_modulus m;
mbedtls_mpi_mod_modulus_init( &m );
@ -579,23 +610,50 @@ void mpi_mod_raw_from_mont_rep( char * input_N, char * input_A, char * input_X )
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &N, &n_limbs, input_N ) );
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &A, &a_limbs, input_A ) );
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &X, &x_limbs, input_X ) );
x_bytes = x_limbs * sizeof(mbedtls_mpi_uint);
/* Test that input does not require more limbs than modulo */
TEST_LE_U(a_limbs, n_limbs);
/* Number to convert must have same number of limbs as modulus */
TEST_EQUAL(a_limbs, n_limbs);
/* Higher-level conversion is in-place, so expected result must have the
* same number of limbs too */
TEST_EQUAL(x_limbs, n_limbs);
size_t limbs = n_limbs;
size_t bytes = limbs * sizeof(mbedtls_mpi_uint);
TEST_EQUAL( 0, mbedtls_mpi_mod_modulus_setup( &m, N, n_limbs,
MBEDTLS_MPI_MOD_REP_MONTGOMERY ) );
MBEDTLS_MPI_MOD_REP_MONTGOMERY ) );
/* 1. Test low-level function first */
/* It has separate output, and requires temporary working storage */
size_t temp_limbs = mbedtls_mpi_core_montmul_working_limbs( limbs );
ASSERT_ALLOC( T, temp_limbs );
ASSERT_ALLOC( R, limbs );
mbedtls_mpi_core_from_mont_rep( R, A, N, n_limbs,
m.rep.mont.mm, T );
/* Test that the low-level function gives the required value */
ASSERT_COMPARE( R, bytes, X, bytes );
/* Test when output is aliased to input */
memcpy( R, A, bytes );
mbedtls_mpi_core_from_mont_rep( R, R, N, n_limbs,
m.rep.mont.mm, T );
ASSERT_COMPARE( R, bytes, X, bytes );
/* 2. Test higher-level Montgomery to cannonical conversion */
/* Convert from Montgomery into cannonical representation */
TEST_EQUAL(0, mbedtls_mpi_mod_raw_from_mont_rep( A, &m ) );
/* The result matches expected value */
ASSERT_COMPARE( A, x_bytes, X, x_bytes );
ASSERT_COMPARE( A, bytes, X, bytes );
exit:
mbedtls_mpi_mod_modulus_free( &m );
mbedtls_free( T );
mbedtls_free( N );
mbedtls_free( A );
mbedtls_free( R );
mbedtls_free( X );
}
/* END_CASE */