diff --git a/library/bignum_core.c b/library/bignum_core.c
index b401fa36c..c1da93d0a 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -540,4 +540,18 @@ cleanup:
     return( ret );
 }
 
+void mbedtls_mpi_core_ct_uint_table_lookup( mbedtls_mpi_uint *dest,
+                                        const mbedtls_mpi_uint *table,
+                                        size_t limbs,
+                                        size_t count,
+                                        size_t index )
+{
+    for( size_t i = 0; i < count; i++ )
+    {
+        unsigned char assign = mbedtls_ct_size_bool_eq( i, index );
+        const mbedtls_mpi_uint *current = table + i * limbs;
+        mbedtls_mpi_core_cond_assign( dest, current, limbs, assign );
+    }
+}
+
 #endif /* MBEDTLS_BIGNUM_C */
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 9a5b89fc6..3618e4200 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -452,4 +452,23 @@ void mbedtls_mpi_core_montmul( mbedtls_mpi_uint *X,
 int mbedtls_mpi_core_get_mont_r2_unsafe( mbedtls_mpi *X,
                                          const mbedtls_mpi *N );
 
+/**
+ * Select an MPI from a table without leaking the index.
+ *
+ * \param dest              The destination buffer. This must point to a writable
+ *                          buffer of at least \p limbs limbs.
+ * \param table             The address of the table. This must point to a readable
+ *                          array of \p count elements of
+ *                          \p limbs limbs each each.
+ * \param limbs             The length of a table entry in limbs.
+ * \param count             The number of elements in \p table.
+ * \param index             The secret table index to look up. This must be in the
+ *                          range `0,..,count-1`.
+ */
+void mbedtls_mpi_core_ct_uint_table_lookup( mbedtls_mpi_uint *dest,
+                                            const mbedtls_mpi_uint *table,
+                                            size_t limbs,
+                                            size_t count,
+                                            size_t index );
+
 #endif /* MBEDTLS_BIGNUM_CORE_H */