sha256_hmac.scala

// cat payload.json | openssl sha256 -hmac 'secret'
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

val payload = scala.io.Source.fromFile("payload.json").mkString
val secret = "secret"
val sha256_HMAC = Mac.getInstance("HmacSHA256")
val secret_key = new SecretKeySpec(secret.getBytes("UTF-8"), "HmacSHA256");
sha256_HMAC.init(secret_key)

val hash = sha256_HMAC.doFinal(payload.getBytes())
val signature = hash.map(b => "%02x".format(b)).mkString