+/* DigestAlgorithmIdentifier flags... */
+
+#define EVP_MD_FLAG_DIGALGID_MASK 0x0018
+
+/* NULL or absent parameter accepted. Use NULL */
+
+#define EVP_MD_FLAG_DIGALGID_NULL 0x0000
+
+/* NULL or absent parameter accepted. Use NULL for PKCS#1 otherwise absent */
+
+#define EVP_MD_FLAG_DIGALGID_ABSENT 0x0008
+
+/* Custom handling via ctrl */
+
+#define EVP_MD_FLAG_DIGALGID_CUSTOM 0x0018
+
+/* Digest ctrls */
+
+#define EVP_MD_CTRL_DIGALGID 0x1
+
+/* Minimum Algorithm specific ctrl value */
+
+#define EVP_MD_CTRL_ALG_CTRL 0x1000
+