diff --git a/src/main/scala/lc/background/taskThread.scala b/src/main/scala/lc/background/taskThread.scala
index e9a9177..33ae997 100644
--- a/src/main/scala/lc/background/taskThread.scala
+++ b/src/main/scala/lc/background/taskThread.scala
@@ -25,7 +25,7 @@ class BackgroundTask(throttle: Int, timeLimit: Int) {
           Captcha.generateChallenge(Parameters("medium", "image/png", "text", Option(Size(0, 0))))
           throttleIn -= 1
         }
-      } catch { case exception: Exception => println(exception.getStackTrace()) }
+      } catch { case exception: Exception => println(exception) }
     }
   }
 
diff --git a/src/main/scala/lc/core/captcha.scala b/src/main/scala/lc/core/captcha.scala
index 146761b..385c6b1 100644
--- a/src/main/scala/lc/core/captcha.scala
+++ b/src/main/scala/lc/core/captcha.scala
@@ -5,34 +5,59 @@ import java.util.UUID
 import java.io.ByteArrayInputStream
 import lc.database.Statements
 import lc.core.CaptchaProviders
+import lc.captchas.interfaces.ChallengeProvider
+import lc.captchas.interfaces.Challenge
+import java.sql.Blob
 
 object Captcha {
 
-  def getCaptcha(id: Id): Array[Byte] = {
-    var image: Array[Byte] = null
-    try {
-      val imagePstmt = Statements.tlStmts.get.imagePstmt
-      imagePstmt.setString(1, id.id)
-      val rs: ResultSet = imagePstmt.executeQuery()
-      if (rs.next()) {
-        val blob = rs.getBlob("image")
+  def getCaptcha(id: Id): Either[Error, Image] = {
+    val blob = getImage(id.id)
+    blob match {
+      case Some(value) => {
         if (blob != null) {
-          image = blob.getBytes(1, blob.length().toInt)
+          Right(Image(value.getBytes(1, value.length().toInt)))
+        } else {
+          Left(Error(ErrorMessageEnum.IMG_MISSING.toString))
         }
       }
-      image
-    } catch {
-      case e: Exception =>
-        println(e)
-        image
+      case None => Left(Error(ErrorMessageEnum.IMG_NOT_FOUND.toString))
     }
   }
 
-  def generateChallenge(param: Parameters): Int = {
+  private def getImage(id: String): Option[Blob] = {
+    val imagePstmt = Statements.tlStmts.get.imagePstmt
+    imagePstmt.setString(1, id)
+    val rs: ResultSet = imagePstmt.executeQuery()
+    if (rs.next()) {
+      Some(rs.getBlob("image"))
+    } else {
+      None
+    }
+  }
+
+  def generateChallenge(param: Parameters): Option[Int] = {
     val provider = CaptchaProviders.getProvider(param)
-    val providerId = provider.getId()
-    val challenge = provider.returnChallenge()
-    val blob = new ByteArrayInputStream(challenge.content)
+    provider match {
+      case Some(value) => {
+        val providerId = value.getId()
+        val challenge = value.returnChallenge()
+        val blob = new ByteArrayInputStream(challenge.content)
+        val token = insertCaptcha(value, challenge, providerId, param, blob)
+        // println("Added new challenge: " + token.toString)
+        token.map(_.toInt)
+      }
+      case None => None
+    }
+  }
+
+  private def insertCaptcha(
+      provider: ChallengeProvider,
+      challenge: Challenge,
+      providerId: String,
+      param: Parameters,
+      blob: ByteArrayInputStream
+  ): Option[Int] = {
     val insertPstmt = Statements.tlStmts.get.insertPstmt
     insertPstmt.setString(1, provider.getId)
     insertPstmt.setString(2, challenge.secret)
@@ -43,63 +68,65 @@ object Captcha {
     insertPstmt.setBlob(7, blob)
     insertPstmt.executeUpdate()
     val rs: ResultSet = insertPstmt.getGeneratedKeys()
-    val token = if (rs.next()) {
-      rs.getInt("token")
+    if (rs.next()) {
+      Some(rs.getInt("token"))
+    } else {
+      None
     }
-    // println("Added new challenge: " + token.toString)
-    token.asInstanceOf[Int]
   }
 
   val allowedInputType = Config.allowedInputType
   val allowedLevels = Config.allowedLevels
   val allowedMedia = Config.allowedMedia
 
-  private def validateParam(param: Parameters): Boolean = {
-    if (
-      allowedLevels.contains(param.level) &&
-      allowedMedia.contains(param.media) &&
-      allowedInputType.contains(param.input_type)
-    )
-      return true
-    else
-      return false
+  private def validateParam(param: Parameters): Array[String] = {
+    var invalid_params = Array[String]()
+    if (!allowedLevels.contains(param.level)) invalid_params :+= "level"
+    if (!allowedMedia.contains(param.media)) invalid_params :+= "media"
+    if (!allowedInputType.contains(param.input_type)) invalid_params :+= "input_type"
+
+    invalid_params
   }
 
-   def getChallenge(param: Parameters): ChallengeResult = {
-    try {
-      val validParam = validateParam(param)
-      if (validParam) {
-        val tokenPstmt = Statements.tlStmts.get.tokenPstmt
-        tokenPstmt.setString(1, param.level)
-        tokenPstmt.setString(2, param.media)
-        tokenPstmt.setString(3, param.input_type)
-        val rs = tokenPstmt.executeQuery()
-        val tokenOpt = if (rs.next()) {
-          Some(rs.getInt("token"))
-        } else {
-          None
+  def getChallenge(param: Parameters): Either[Error, Id] = {
+    val validParam = validateParam(param)
+    if (validParam.isEmpty) {
+      val tokenOpt = getToken(param)
+      val token = tokenOpt.orElse(generateChallenge(param))
+      token match {
+        case Some(value) => {
+          val uuid = getUUID(value)
+          updateAttempted(uuid)
+          Right(Id(uuid))
         }
-        val updateAttemptedPstmt = Statements.tlStmts.get.updateAttemptedPstmt
-        val token = tokenOpt.getOrElse(generateChallenge(param))
-        val result = if (token != -1) {
-          val uuid = getUUID(token)
-          updateAttemptedPstmt.setString(1, uuid)
-          updateAttemptedPstmt.executeUpdate()
-          Id(uuid)
-        } else {
-          Error(ErrorMessageEnum.NO_CAPTCHA.toString)
+        case None => {
+          Left(Error(ErrorMessageEnum.NO_CAPTCHA.toString))
         }
-        result
-      } else {
-        Error(ErrorMessageEnum.INVALID_PARAM.toString)
       }
-    } catch {
-      case e: Exception =>
-        println(e)
-        Error(ErrorMessageEnum.SMW.toString)
+    } else {
+      Left(Error(ErrorMessageEnum.INVALID_PARAM.toString + " => " + validParam.mkString(", ")))
     }
   }
 
+  private def getToken(param: Parameters): Option[Int] = {
+    val tokenPstmt = Statements.tlStmts.get.tokenPstmt
+    tokenPstmt.setString(1, param.level)
+    tokenPstmt.setString(2, param.media)
+    tokenPstmt.setString(3, param.input_type)
+    val rs = tokenPstmt.executeQuery()
+    if (rs.next()) {
+      Some(rs.getInt("token"))
+    } else {
+      None
+    }
+  }
+
+  private def updateAttempted(uuid: String): Unit = {
+    val updateAttemptedPstmt = Statements.tlStmts.get.updateAttemptedPstmt
+    updateAttemptedPstmt.setString(1, uuid)
+    updateAttemptedPstmt.executeUpdate()
+  }
+
   private def getUUID(id: Int): String = {
     val uuid = UUID.randomUUID().toString
     val mapPstmt = Statements.tlStmts.get.mapPstmt
@@ -109,24 +136,38 @@ object Captcha {
     uuid
   }
 
-  def checkAnswer(answer: Answer): Result = {
+  def checkAnswer(answer: Answer): Either[Error, Success] = {
+    val challenge = getSecret(answer.id)
+    challenge match {
+      case None => Right(Success(ResultEnum.EXPIRED.toString))
+      case Some(value) => {
+        val (provider, secret) = value
+        val check = CaptchaProviders.getProviderById(provider).checkAnswer(secret, answer.answer)
+        deleteCaptcha(answer.id)
+        val result = if (check) ResultEnum.TRUE.toString else ResultEnum.FALSE.toString
+        Right(Success(result))
+      }
+    }
+  }
+
+  private def getSecret(id: String): Option[(String, String)] = {
     val selectPstmt = Statements.tlStmts.get.selectPstmt
     selectPstmt.setInt(1, Config.captchaExpiryTimeLimit)
-    selectPstmt.setString(2, answer.id)
+    selectPstmt.setString(2, id)
     val rs: ResultSet = selectPstmt.executeQuery()
-    val psOpt = if (rs.first()) {
+    if (rs.first()) {
       val secret = rs.getString("secret")
       val provider = rs.getString("provider")
-      val check = CaptchaProviders.getProviderById(provider).checkAnswer(secret, answer.answer)
-      val result = if (check) ResultEnum.TRUE.toString else ResultEnum.FALSE.toString
-      result
+      Some(provider, secret)
     } else {
-      ResultEnum.EXPIRED.toString
+      None
     }
+  }
+
+  private def deleteCaptcha(id: String): Unit = {
     val deleteAnswerPstmt = Statements.tlStmts.get.deleteAnswerPstmt
-    deleteAnswerPstmt.setString(1, answer.id)
+    deleteAnswerPstmt.setString(1, id)
     deleteAnswerPstmt.executeUpdate()
-    Result(psOpt)
   }
 
   def display(): Unit = {
diff --git a/src/main/scala/lc/core/captchaFields.scala b/src/main/scala/lc/core/captchaFields.scala
index 9a6e223..80e691d 100644
--- a/src/main/scala/lc/core/captchaFields.scala
+++ b/src/main/scala/lc/core/captchaFields.scala
@@ -38,6 +38,8 @@ object ErrorMessageEnum extends Enumeration {
 
   val SMW: Value = Value("Oops, something went worng!")
   val INVALID_PARAM: Value = Value("Parameters invalid or missing")
-  val NO_CAPTCHA: Value = Value("No captcha for the provided parameters")
+  val IMG_MISSING: Value = Value("Image missing")
+  val IMG_NOT_FOUND: Value = Value("Image not found")
+  val NO_CAPTCHA: Value = Value("No captcha for the provided parameters. Change config options.")
   val BAD_METHOD: Value = Value("Bad request method")
 }
diff --git a/src/main/scala/lc/core/captchaProviders.scala b/src/main/scala/lc/core/captchaProviders.scala
index 1174ade..8a61841 100644
--- a/src/main/scala/lc/core/captchaProviders.scala
+++ b/src/main/scala/lc/core/captchaProviders.scala
@@ -12,7 +12,7 @@ object CaptchaProviders {
     "GifCaptcha" -> new GifCaptcha,
     "ShadowTextCaptcha" -> new ShadowTextCaptcha,
     "RainDropsCaptcha" -> new RainDropsCP,
-    "DebugCaptcha" -> new DebugCaptcha,
+    "DebugCaptcha" -> new DebugCaptcha
     //"LabelCaptcha" -> new LabelCaptcha
   )
 
@@ -55,13 +55,16 @@ object CaptchaProviders {
     providerFilter
   }
 
-  def getProvider(param: Parameters): ChallengeProvider = {
+  def getProvider(param: Parameters): Option[ChallengeProvider] = {
     val providerConfig = filterProviderByParam(param).toList
-    if (providerConfig.length == 0) throw new NoSuchElementException(ErrorMessageEnum.NO_CAPTCHA.toString)
-    val randomIndex = getNextRandomInt(providerConfig.length)
-    val providerIndex = providerConfig(randomIndex)._1
-    val selectedProvider = providers(providerIndex)
-    selectedProvider.configure(providerConfig(randomIndex)._2)
-    selectedProvider
+    if (providerConfig.length > 0) {
+      val randomIndex = getNextRandomInt(providerConfig.length)
+      val providerIndex = providerConfig(randomIndex)._1
+      val selectedProvider = providers(providerIndex)
+      selectedProvider.configure(providerConfig(randomIndex)._2)
+      Some(selectedProvider)
+    } else {
+      None
+    }
   }
 }
diff --git a/src/main/scala/lc/core/config.scala b/src/main/scala/lc/core/config.scala
index 233108f..a0adc77 100644
--- a/src/main/scala/lc/core/config.scala
+++ b/src/main/scala/lc/core/config.scala
@@ -49,42 +49,42 @@ object Config {
   val allowedInputType: Set[String] = captchaConfig.flatMap(_.allowedInputType).toSet
 
   private def getDefaultConfig(): String = {
-    val defaultConfigMap = 
+    val defaultConfigMap =
       (AttributesEnum.RANDOM_SEED.toString -> 20) ~
-      (AttributesEnum.PORT.toString -> 8888) ~
-      (AttributesEnum.CAPTCHA_EXPIRY_TIME_LIMIT.toString -> 5) ~
-      (AttributesEnum.THROTTLE.toString -> 10) ~
-      (AttributesEnum.THREAD_DELAY.toString -> 2) ~
-      ("captchas" -> List(
-        (
-          (AttributesEnum.NAME.toString -> "FilterChallenge") ~
-          (ParametersEnum.ALLOWEDLEVELS.toString -> List("medium", "hard")) ~
-          (ParametersEnum.ALLOWEDMEDIA.toString -> List("image/png")) ~
-          (ParametersEnum.ALLOWEDINPUTTYPE.toString -> List("text")) ~
-          (AttributesEnum.CONFIG.toString -> JObject())
-        ),
-        (
-          (AttributesEnum.NAME.toString -> "GifCaptcha") ~
-          (ParametersEnum.ALLOWEDLEVELS.toString -> List("hard")) ~
-          (ParametersEnum.ALLOWEDMEDIA.toString -> List("image/gif")) ~
-          (ParametersEnum.ALLOWEDINPUTTYPE.toString -> List("text")) ~
-          (AttributesEnum.CONFIG.toString -> JObject())
-        ),
-        (
-          (AttributesEnum.NAME.toString -> "ShadowTextCaptcha") ~
-          (ParametersEnum.ALLOWEDLEVELS.toString -> List("easy")) ~
-          (ParametersEnum.ALLOWEDMEDIA.toString -> List("image/png")) ~
-          (ParametersEnum.ALLOWEDINPUTTYPE.toString -> List("text")) ~
-          (AttributesEnum.CONFIG.toString -> JObject())
-        ),
-        (
-          (AttributesEnum.NAME.toString -> "RainDropsCaptcha") ~
-          (ParametersEnum.ALLOWEDLEVELS.toString -> List("easy", "medium")) ~
-          (ParametersEnum.ALLOWEDMEDIA.toString -> List("image/gif")) ~
-          (ParametersEnum.ALLOWEDINPUTTYPE.toString -> List("text")) ~
-          (AttributesEnum.CONFIG.toString -> JObject())
-        )
-      ))
+        (AttributesEnum.PORT.toString -> 8888) ~
+        (AttributesEnum.CAPTCHA_EXPIRY_TIME_LIMIT.toString -> 5) ~
+        (AttributesEnum.THROTTLE.toString -> 10) ~
+        (AttributesEnum.THREAD_DELAY.toString -> 2) ~
+        ("captchas" -> List(
+          (
+            (AttributesEnum.NAME.toString -> "FilterChallenge") ~
+              (ParametersEnum.ALLOWEDLEVELS.toString -> List("medium", "hard")) ~
+              (ParametersEnum.ALLOWEDMEDIA.toString -> List("image/png")) ~
+              (ParametersEnum.ALLOWEDINPUTTYPE.toString -> List("text")) ~
+              (AttributesEnum.CONFIG.toString -> JObject())
+          ),
+          (
+            (AttributesEnum.NAME.toString -> "GifCaptcha") ~
+              (ParametersEnum.ALLOWEDLEVELS.toString -> List("hard")) ~
+              (ParametersEnum.ALLOWEDMEDIA.toString -> List("image/gif")) ~
+              (ParametersEnum.ALLOWEDINPUTTYPE.toString -> List("text")) ~
+              (AttributesEnum.CONFIG.toString -> JObject())
+          ),
+          (
+            (AttributesEnum.NAME.toString -> "ShadowTextCaptcha") ~
+              (ParametersEnum.ALLOWEDLEVELS.toString -> List("easy")) ~
+              (ParametersEnum.ALLOWEDMEDIA.toString -> List("image/png")) ~
+              (ParametersEnum.ALLOWEDINPUTTYPE.toString -> List("text")) ~
+              (AttributesEnum.CONFIG.toString -> JObject())
+          ),
+          (
+            (AttributesEnum.NAME.toString -> "RainDropsCaptcha") ~
+              (ParametersEnum.ALLOWEDLEVELS.toString -> List("easy", "medium")) ~
+              (ParametersEnum.ALLOWEDMEDIA.toString -> List("image/gif")) ~
+              (ParametersEnum.ALLOWEDINPUTTYPE.toString -> List("text")) ~
+              (AttributesEnum.CONFIG.toString -> JObject())
+          )
+        ))
 
     pretty(render(defaultConfigMap))
   }
diff --git a/src/main/scala/lc/core/models.scala b/src/main/scala/lc/core/models.scala
index 834607f..b06a1aa 100644
--- a/src/main/scala/lc/core/models.scala
+++ b/src/main/scala/lc/core/models.scala
@@ -1,13 +1,16 @@
 package lc.core
 
-sealed trait ChallengeResult
+import org.json4s.jackson.Serialization.write
+import lc.core.Config.formats
+
+trait ByteConvert { def toBytes(): Array[Byte] }
 case class Size(height: Int, width: Int)
 case class Parameters(level: String, media: String, input_type: String, size: Option[Size])
-case class Id(id: String) extends ChallengeResult
-case class Image(image: Array[Byte]) extends ChallengeResult
+case class Id(id: String) extends ByteConvert { def toBytes(): Array[Byte] = { write(this).getBytes } }
+case class Image(image: Array[Byte]) extends ByteConvert { def toBytes(): Array[Byte] = { image } }
 case class Answer(answer: String, id: String)
-case class Result(result: String)
-case class Error(message: String) extends ChallengeResult
+case class Success(result: String) extends ByteConvert { def toBytes(): Array[Byte] = { write(this).getBytes } }
+case class Error(message: String) extends ByteConvert { def toBytes(): Array[Byte] = { write(this).getBytes } }
 case class Response(statusCode: Int, message: Array[Byte])
 case class CaptchaConfig(
     name: String,
diff --git a/src/main/scala/lc/server/Server.scala b/src/main/scala/lc/server/Server.scala
index 26089f2..b5c2848 100644
--- a/src/main/scala/lc/server/Server.scala
+++ b/src/main/scala/lc/server/Server.scala
@@ -1,18 +1,16 @@
 package lc.server
 
-import org.json4s.DefaultFormats
 import org.json4s.jackson.JsonMethods.parse
-import org.json4s.jackson.Serialization.write
 import lc.core.Captcha
 import lc.core.ErrorMessageEnum
-import lc.core.{Parameters, Id, Answer, Response}
+import lc.core.{Parameters, Id, Answer, Response, Error, ByteConvert}
 import org.json4s.JsonAST.JValue
 import com.sun.net.httpserver.{HttpServer, HttpExchange}
 import java.net.InetSocketAddress
+import lc.core.Config.formats
 
 class Server(port: Int) {
 
-  implicit val formats: DefaultFormats.type = DefaultFormats
   val server: HttpServer = HttpServer.create(new InetSocketAddress(port), 32)
   server.setExecutor(java.util.concurrent.Executors.newCachedThreadPool())
 
@@ -24,14 +22,19 @@ class Server(port: Int) {
   }
 
   private val eqPattern = java.util.regex.Pattern.compile("=")
-  private def getPathParameter(ex: HttpExchange): String = {
+  private def getPathParameter(ex: HttpExchange): Either[String, String] = {
     try {
       val query = ex.getRequestURI.getQuery
-      eqPattern.split(query)(1)
+      val param = eqPattern.split(query)
+      if (param(0) == "id") {
+        Right(param(1))
+      } else {
+        Left(ErrorMessageEnum.INVALID_PARAM.toString + "=> id")
+      }
     } catch {
       case exception: ArrayIndexOutOfBoundsException => {
-        println(exception.getStackTrace)
-        throw new Exception(ErrorMessageEnum.INVALID_PARAM.toString)
+        println(exception)
+        Left(ErrorMessageEnum.INVALID_PARAM.toString + "=> id")
       }
     }
   }
@@ -44,15 +47,25 @@ class Server(port: Int) {
   }
 
   private def getException(exception: Exception): Response = {
-    println(exception.printStackTrace)
-    val message = ("message" -> exception.getMessage)
-    val messageByte = write(message).getBytes
-    Response(500, messageByte)
+    println(exception)
+    val message = Error(exception.getMessage)
+    Response(500, message.toBytes())
   }
 
   private def getBadRequestError(): Response = {
-    val message = ("message" -> ErrorMessageEnum.BAD_METHOD.toString)
-    Response(405, write(message).getBytes)
+    val message = Error(ErrorMessageEnum.BAD_METHOD.toString)
+    Response(405, message.toBytes())
+  }
+
+  private def getResponse(response: Either[Error, ByteConvert]): Response = {
+    response match {
+      case Right(value) => {
+        Response(200, value.toBytes())
+      }
+      case Left(value) => {
+        Response(500, value.toBytes())
+      }
+    }
   }
 
   private def makeApiWorker(path: String, f: (String, HttpExchange) => Response): Unit = {
@@ -85,7 +98,7 @@ class Server(port: Int) {
         val json = getRequestJson(ex)
         val param = json.extract[Parameters]
         val id = Captcha.getChallenge(param)
-        Response(200, write(id).getBytes)
+        getResponse(id)
       } else {
         getBadRequestError()
       }
@@ -97,9 +110,14 @@ class Server(port: Int) {
     (method: String, ex: HttpExchange) => {
       if (method == "GET") {
         val param = getPathParameter(ex)
-        val id = Id(param)
-        val image = Captcha.getCaptcha(id)
-        Response(200, image)
+        val result = param match {
+          case Right(value) => {
+            val id = Id(value)
+            Captcha.getCaptcha(id)
+          }
+          case Left(value) => Left(Error(value))
+        }
+        getResponse(result)
       } else {
         getBadRequestError()
       }
@@ -113,7 +131,7 @@ class Server(port: Int) {
         val json = getRequestJson(ex)
         val answer = json.extract[Answer]
         val result = Captcha.checkAnswer(answer)
-        Response(200, write(result).getBytes)
+        getResponse(result)
       } else {
         getBadRequestError()
       }