the correct way to use SecureRandom in clojure. automatically reseeds every ttl ms

gistfile1.clj

(defn- reseeding-prng [ttl]
	(let [state (atom {})]
		(fn []
			(let [now (.getTime (java.util.Date.))]
				(when (> (- now (:last-seeded @state 0)) ttl)
					(let [new-generator (java.security.SecureRandom/getInstance "SHA1PRNG" "SUN")]
						(.nextBytes new-generator (byte-array 0))
						(swap! state assoc :last-seeded now :generator new-generator)))
				(:generator @state)))))

(def ^:private prng (reseeding-prng (* 60 60 1000)))

(defn- random-id []
	(.toString (BigInteger. 160 (prng)) 36))

don't use SHA1 these days though