hmac-sha-256

(ns hmac 
  (:import (javax.crypto Mac) (javax.crypto.spec SecretKeySpec))
)

(defn secret-key-inst [key mac]
  (SecretKeySpec. (.getBytes key) (.getAlgorithm mac))
)

(defn sign[key string]
  "Returns the signature of a string with a given key, using a SHA-256 HMAC."
  (let [mac (Mac/getInstance "HMACSHA256")
    secret-key (secret-key-inst key mac)]
    (-> (doto mac
      (.init secret-key)
      (.update (.getBytes string)))
      .doFinal)
  )
)

(println
  (apply str (map #(format "%x" %) (sign "key" "message")))
)