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Convert comments over to X rather than N

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Signed-off-by: Paul Elliott <paul.elliott@arm.com>
This commit is contained in:
Paul Elliott 2023-05-16 17:55:44 +01:00
parent 6b1f7f101f
commit c05f51ded9
1 changed files with 12 additions and 12 deletions
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24
library/ecp_curves.c
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@ -5472,14 +5472,14 @@ cleanup:
/* /*
* Fast quasi-reduction modulo p448 = 2^448 - 2^224 - 1 * Fast quasi-reduction modulo p448 = 2^448 - 2^224 - 1
* Write N as A0 + 2^448 A1 and A1 as B0 + 2^224 B1, and return * Write X as A0 + 2^448 A1 and A1 as B0 + 2^224 B1, and return A0 + A1 + B1 +
* A0 + A1 + B1 + (B0 + B1) * 2^224. This is different to the reference * (B0 + B1) * 2^224. This is different to the reference implementation of
* implementation of Curve448, which uses its own special 56-bit limbs rather * Curve448, which uses its own special 56-bit limbs rather than a generic
* than a generic bignum library. We could squeeze some extra speed out on * bignum library. We could squeeze some extra speed out on 32-bit machines by
* 32-bit machines by splitting N up into 32-bit limbs and doing the * splitting N up into 32-bit limbs and doing the arithmetic using the limbs
* arithmetic using the limbs directly as we do for the NIST primes above, * directly as we do for the NIST primes above, but for 64-bit targets it should
* but for 64-bit targets it should use half the number of operations if we do * use half the number of operations if we do the reduction with 224-bit limbs,
* the reduction with 224-bit limbs, since mpi_add_mpi will then use 64-bit adds. * since mpi_add_mpi will then use 64-bit adds.
*/ */
MBEDTLS_STATIC_TESTABLE MBEDTLS_STATIC_TESTABLE
int mbedtls_ecp_mod_p448(mbedtls_mpi_uint *X, size_t X_limbs) int mbedtls_ecp_mod_p448(mbedtls_mpi_uint *X, size_t X_limbs)
@ -5495,7 +5495,7 @@ int mbedtls_ecp_mod_p448(mbedtls_mpi_uint *X, size_t X_limbs)
const size_t Q_limbs = M_limbs; const size_t Q_limbs = M_limbs;
if (M_limbs > P448_WIDTH) { if (M_limbs > P448_WIDTH) {
/* Shouldn't be called with N larger than 2^896! */ /* Shouldn't be called with X larger than 2^896! */
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA; return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
} }
@ -5519,7 +5519,7 @@ int mbedtls_ecp_mod_p448(mbedtls_mpi_uint *X, size_t X_limbs)
memset(M, 0, (M_limbs * ciL)); memset(M, 0, (M_limbs * ciL));
/* Do not copy into the overflow limb, as this would read past the end of /* Do not copy into the overflow limb, as this would read past the end of
* N. */ * X. */
memcpy(M, X + P448_WIDTH, ((M_limbs - 1) * ciL)); memcpy(M, X + P448_WIDTH, ((M_limbs - 1) * ciL));
/* N = A0 */ /* N = A0 */
@ -5527,10 +5527,10 @@ int mbedtls_ecp_mod_p448(mbedtls_mpi_uint *X, size_t X_limbs)
X[i] = 0; X[i] = 0;
} }
/* N += A1 - Carry here dealt with by oversize M and N. */ /* X += A1 - Carry here dealt with by oversize M and X. */
(void) mbedtls_mpi_core_add(X, X, M, M_limbs); (void) mbedtls_mpi_core_add(X, X, M, M_limbs);
/* Q = B1, N += B1 */ /* Q = B1, X += B1 */
memcpy(Q, M, (Q_limbs * ciL)); memcpy(Q, M, (Q_limbs * ciL));
mbedtls_mpi_core_shift_r(Q, Q_limbs, 224); mbedtls_mpi_core_shift_r(Q, Q_limbs, 224);