Bignum core: random: prototype
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 120fa18..eeca41e 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -512,6 +512,43 @@
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
+/** Generate a random number uniformly in a range.
+ *
+ * This function generates a random number between \p min inclusive and
+ * \p N exclusive.
+ *
+ * The procedure complies with RFC 6979 §3.3 (deterministic ECDSA)
+ * when the RNG is a suitably parametrized instance of HMAC_DRBG
+ * and \p min is \c 1.
+ *
+ * \note There are `N - min` possible outputs. The lower bound
+ * \p min can be reached, but the upper bound \p N cannot.
+ *
+ * \param X The destination MPI, with \p limbs limbs.
+ * It must not be aliased with \p N or otherwise overlap it.
+ * \param min The minimum value to return.
+ * \param N The upper bound of the range, exclusive, with \p limbs limbs.
+ * In other words, this is one plus the maximum value to return.
+ * \p N must be strictly larger than \p min.
+ * \param limbs The number of limbs of \p N and \p X.
+ * This must not be 0.
+ * \param f_rng The RNG function to use. This must not be \c NULL.
+ * \param p_rng The RNG parameter to be passed to \p f_rng.
+ *
+ * \return \c 0 if successful.
+ * \return #MBEDTLS_ERR_MPI_NOT_ACCEPTABLE if the implementation was
+ * unable to find a suitable value within a limited number
+ * of attempts. This has a negligible probability if \p N
+ * is significantly larger than \p min, which is the case
+ * for all usual cryptographic applications.
+ */
+int mbedtls_mpi_core_random( mbedtls_mpi_uint *X,
+ mbedtls_mpi_uint min,
+ const mbedtls_mpi_uint *N,
+ size_t limbs,
+ int (*f_rng)(void *, unsigned char *, size_t),
+ void *p_rng );
+
/* BEGIN MERGE SLOT 1 */
/**