+/* get a clone of a BIGNUM with changed flags, for *temporary* use only
+ * (the two BIGNUMs cannot not be used in parallel!) */
+#define BN_with_flags(dest,b,n) ((dest)->d=(b)->d, \
+ (dest)->top=(b)->top, \
+ (dest)->dmax=(b)->dmax, \
+ (dest)->neg=(b)->neg, \
+ (dest)->flags=(((dest)->flags & BN_FLG_MALLOCED) \
+ | ((b)->flags & ~BN_FLG_MALLOCED) \
+ | BN_FLG_STATIC_DATA \
+ | (n)))
+