ed using any given <i>libctx</i> and property query string <i>propq</i>. It takes parameters <i>subalg</i> and further <i>params</i>, both of which may be NULL if not needed. If <i>out</i> is not NULL, it places the result in the memory pointed at by <i>out</i>, but only if <i>outsize</i> is sufficient (otherwise no computation is made). If <i>out</i> is NULL, it allocates and uses a buffer of suitable length, which will be returned on success and must be freed by the caller. In either case, also on error, 