(defn verify-message [signature message]
  (let [verifier (Signature/getInstance "SHA1withRSA")]
    (.initVerify verifier publickey)
    (.update verifier (.getBytes message))
    (.verify verifier signature)))

# With the thrush macro:
(defn verify-message [signature message]
  (-> (Signature/getInstance "SHA1withRSA")
    (.initVerify publickey)
    (.update (.getBytes message)
    (.verify signature)))