diff --git a/Database/EventStore.hs b/Database/EventStore.hs
--- a/Database/EventStore.hs
+++ b/Database/EventStore.hs
@@ -14,10 +14,13 @@
     ( Event
     , EventData
     , Connection
+    , Credentials
     , ExpectedVersion(..)
     , HostName
     , Port
+    , Settings(..)
     , Subscription(..)
+    , credentials
       -- * Result
     , AllEventsSlice(..)
     , DeleteResult(..)
@@ -25,6 +28,13 @@
     , ReadResult(..)
     , RecordedEvent(..)
     , StreamEventsSlice(..)
+    , Position(..)
+    , ReadDirection(..)
+    , ReadAllResult(..)
+    , ReadEventResult(..)
+    , ResolvedEvent(..)
+    , ReadStreamResult(..)
+    , DropReason(..)
     , eventResolved
     , resolvedEventOriginal
     , resolvedEventOriginalStreamId
@@ -101,7 +111,7 @@
 --   this way
 connect :: Settings -> HostName -> Port -> IO Connection
 connect settings host port = do
-    processor <- newProcessor 3
+    processor <- newProcessor settings
     processorConnect processor host port
 
     return $ Connection processor settings
diff --git a/Database/EventStore/Internal/Manager/Operation.hs b/Database/EventStore/Internal/Manager/Operation.hs
--- a/Database/EventStore/Internal/Manager/Operation.hs
+++ b/Database/EventStore/Internal/Manager/Operation.hs
@@ -71,23 +71,23 @@
       }
 
 --------------------------------------------------------------------------------
-createOperation :: OperationParams -> Operation
-createOperation params =
+createOperation :: Settings -> OperationParams -> Operation
+createOperation sett params =
     Operation
-    { operationCreatePackage = createPackage params
+    { operationCreatePackage = createPackage sett params
     , operationInspect       = inspection params
     }
 
 --------------------------------------------------------------------------------
-createPackage :: OperationParams -> UUID -> IO Package
-createPackage OperationParams{..} uuid = do
+createPackage :: Settings -> OperationParams -> UUID -> IO Package
+createPackage Settings{..} OperationParams{..} uuid = do
     req <- opRequest
 
     let pack = Package
                { packageCmd         = opRequestCmd
                , packageCorrelation = uuid
-               , packageFlag        = None
                , packageData        = runPut $ encodeMessage req
+               , packageCred        = s_credentials
                }
 
     return pack
@@ -123,11 +123,12 @@
 data Response = Response !Package !Operation
 
 --------------------------------------------------------------------------------
-operationNetwork :: (Package -> Reactive ())
+operationNetwork :: Settings
+                 -> (Package -> Reactive ())
                  -> Reactive ()
                  -> Event Package
                  -> Reactive (OperationParams -> Reactive ())
-operationNetwork push_pkg push_reco e_pkg = do
+operationNetwork sett push_pkg push_reco e_pkg = do
     (on_new, push_new) <- newEvent
     (on_reg, push_reg) <- newEvent
     (on_rem, push_rem) <- newEvent
@@ -140,7 +141,7 @@
 
     let resp_e = filterJust $ snapshot response e_pkg mgr_b
 
-        on_new_op = fmap createOperation on_new <> on_ret
+        on_new_op = fmap (createOperation sett) on_new <> on_ret
 
         push_reg_io   = pushAsync2 $ \uuid op -> push_reg $ Register uuid op
         push_rem_io   = pushAsync (push_rem . Remove)
diff --git a/Database/EventStore/Internal/Manager/Subscription.hs b/Database/EventStore/Internal/Manager/Subscription.hs
--- a/Database/EventStore/Internal/Manager/Subscription.hs
+++ b/Database/EventStore/Internal/Manager/Subscription.hs
@@ -15,7 +15,8 @@
 --
 --------------------------------------------------------------------------------
 module Database.EventStore.Internal.Manager.Subscription
-    ( Subscription(..)
+    ( DropReason (..)
+    , Subscription(..)
     , subscriptionNetwork
     ) where
 
@@ -85,10 +86,10 @@
 
 --------------------------------------------------------------------------------
 data DropReason
-    = Unsubscribed
-    | AccessDenied
-    | NotFound
-    | PersistentSubscriptionDeleted
+    = D_Unsubscribed
+    | D_AccessDenied
+    | D_NotFound
+    | D_PersistentSubscriptionDeleted
     deriving (Enum, Eq, Show)
 
 --------------------------------------------------------------------------------
@@ -215,10 +216,11 @@
 type NewSubscription = (Subscription -> IO ()) -> Text -> Bool -> IO ()
 
 --------------------------------------------------------------------------------
-subscriptionNetwork :: (Package -> Reactive ())
+subscriptionNetwork :: Settings
+                    -> (Package -> Reactive ())
                     -> Event Package
                     -> Reactive NewSubscription
-subscriptionNetwork push_pkg e_pkg = do
+subscriptionNetwork sett push_pkg e_pkg = do
     (on_sub, push_sub) <- newEvent
     (on_rem, push_rem) <- newEvent
 
@@ -247,7 +249,7 @@
                      , _subResolveLinkTos = res_lnk_tos
                      }
 
-    _ <- listen on_sub (push_pkg_io . createSubscribePackage)
+    _ <- listen on_sub (push_pkg_io . createSubscribePackage sett)
 
     _ <- listen on_app $ \(Appeared sub evt) ->
         atomically $ writeTChan (subEventChan sub) (Right evt)
@@ -258,13 +260,13 @@
     return push_sub_io
 
 --------------------------------------------------------------------------------
-createSubscribePackage :: Subscribe -> Package
-createSubscribePackage Subscribe{..} =
+createSubscribePackage :: Settings -> Subscribe -> Package
+createSubscribePackage Settings{..} Subscribe{..} =
     Package
     { packageCmd         = 0xC0
-    , packageFlag        = None
     , packageCorrelation = _subId
     , packageData        = runPut $ encodeMessage msg
+    , packageCred        = s_credentials
     }
   where
     msg = subscribeToStream _subStream _subResolveLinkTos
@@ -290,7 +292,7 @@
     go | packageCmd == subscriptionDropped = do
              sub <- M.lookup packageCorrelation _subscriptions
              msg <- maybeDecodeMessage packageData
-             let reason  = fromMaybe Unsubscribed $ getField $ dropReason msg
+             let reason  = fromMaybe D_Unsubscribed $ getField $ dropReason msg
                  dropped = Dropped
                            { droppedReason = reason
                            , droppedSub    = sub
diff --git a/Database/EventStore/Internal/Operation/DeleteStreamOperation.hs b/Database/EventStore/Internal/Operation/DeleteStreamOperation.hs
--- a/Database/EventStore/Internal/Operation/DeleteStreamOperation.hs
+++ b/Database/EventStore/Internal/Operation/DeleteStreamOperation.hs
@@ -82,7 +82,7 @@
     , opResponseCmd = 0x8B
 
     , opRequest =
-        let req_master  = _requireMaster settings
+        let req_master  = s_requireMaster settings
             exp_ver_int = expVersionInt32 exp_ver
             request     = newDeleteStream stream_id
                                           exp_ver_int
diff --git a/Database/EventStore/Internal/Operation/ReadAllEventsOperation.hs b/Database/EventStore/Internal/Operation/ReadAllEventsOperation.hs
--- a/Database/EventStore/Internal/Operation/ReadAllEventsOperation.hs
+++ b/Database/EventStore/Internal/Operation/ReadAllEventsOperation.hs
@@ -14,6 +14,7 @@
 --------------------------------------------------------------------------------
 module Database.EventStore.Internal.Operation.ReadAllEventsOperation
     ( AllEventsSlice(..)
+    , ReadAllResult(..)
     , readAllEventsOperation
     ) where
 
@@ -135,7 +136,7 @@
     , opResponseCmd = resp
 
     , opRequest =
-        let req_master = _requireMaster settings
+        let req_master = s_requireMaster settings
             request    = newReadAllEvents c_pos
                                           p_pos
                                           max_c
diff --git a/Database/EventStore/Internal/Operation/ReadEventOperation.hs b/Database/EventStore/Internal/Operation/ReadEventOperation.hs
--- a/Database/EventStore/Internal/Operation/ReadEventOperation.hs
+++ b/Database/EventStore/Internal/Operation/ReadEventOperation.hs
@@ -14,6 +14,7 @@
 --------------------------------------------------------------------------------
 module Database.EventStore.Internal.Operation.ReadEventOperation
     ( ReadResult(..)
+    , ReadEventResult(..)
     , readEventOperation
     ) where
 
@@ -119,7 +120,7 @@
     , opResponseCmd = 0xB1
 
     , opRequest =
-        let req_master = _requireMaster settings
+        let req_master = s_requireMaster settings
             request    = newReadEvent stream_id
                                       evt_num
                                       res_link_tos
diff --git a/Database/EventStore/Internal/Operation/ReadStreamEventsOperation.hs b/Database/EventStore/Internal/Operation/ReadStreamEventsOperation.hs
--- a/Database/EventStore/Internal/Operation/ReadStreamEventsOperation.hs
+++ b/Database/EventStore/Internal/Operation/ReadStreamEventsOperation.hs
@@ -13,6 +13,7 @@
 --------------------------------------------------------------------------------
 module Database.EventStore.Internal.Operation.ReadStreamEventsOperation
     ( StreamEventsSlice(..)
+    , ReadStreamResult(..)
     , readStreamEventsOperation
     ) where
 
@@ -136,7 +137,7 @@
     , opResponseCmd = resp
 
     , opRequest =
-        let req_master = _requireMaster settings
+        let req_master = s_requireMaster settings
             request    = newReadStreamEvents stream_id
                                              start
                                              cnt
diff --git a/Database/EventStore/Internal/Operation/TransactionStartOperation.hs b/Database/EventStore/Internal/Operation/TransactionStartOperation.hs
--- a/Database/EventStore/Internal/Operation/TransactionStartOperation.hs
+++ b/Database/EventStore/Internal/Operation/TransactionStartOperation.hs
@@ -52,7 +52,7 @@
     , opResponseCmd = 0x85
 
     , opRequest =
-        let req_master  = _requireMaster settings
+        let req_master  = s_requireMaster settings
             exp_ver_int = expVersionInt32 exp_ver
             request     = newTransactionStart stream_id
                                               exp_ver_int
@@ -164,7 +164,7 @@
     }
   where
     settings   = _transSettings env
-    req_master = _requireMaster settings
+    req_master = s_requireMaster settings
 
 --------------------------------------------------------------------------------
 transactionCommitOperation :: TransactionEnv
@@ -187,7 +187,7 @@
     }
   where
     settings   = _transSettings env
-    req_master = _requireMaster settings
+    req_master = s_requireMaster settings
 
 --------------------------------------------------------------------------------
 inspectWrite :: TransactionEnv
diff --git a/Database/EventStore/Internal/Operation/WriteEventsOperation.hs b/Database/EventStore/Internal/Operation/WriteEventsOperation.hs
--- a/Database/EventStore/Internal/Operation/WriteEventsOperation.hs
+++ b/Database/EventStore/Internal/Operation/WriteEventsOperation.hs
@@ -87,7 +87,7 @@
     , opRequest = do
         new_evts <- traverse eventToNewEvent evts
 
-        let require_master = _requireMaster settings
+        let require_master = s_requireMaster settings
             exp_ver_int32  = expVersionInt32 exp_ver
             request        = newWriteEvents evt_stream
                                                   exp_ver_int32
diff --git a/Database/EventStore/Internal/Packages.hs b/Database/EventStore/Internal/Packages.hs
--- a/Database/EventStore/Internal/Packages.hs
+++ b/Database/EventStore/Internal/Packages.hs
@@ -19,6 +19,7 @@
 
 --------------------------------------------------------------------------------
 import qualified Data.ByteString as B
+import           Data.Foldable (for_)
 
 --------------------------------------------------------------------------------
 import Data.Serialize.Put
@@ -36,9 +37,9 @@
     uuid <- randomIO
     let pack = Package
                { packageCmd         = 0x01
-               , packageFlag        = None
                , packageCorrelation = uuid
                , packageData        = B.empty
+               , packageCred        = Nothing
                }
 
     return pack
@@ -48,24 +49,35 @@
 heartbeatResponsePackage uuid =
     Package
     { packageCmd         = 0x02
-    , packageFlag        = None
     , packageCorrelation = uuid
     , packageData        = B.empty
+    , packageCred        = Nothing
     }
 
 --------------------------------------------------------------------------------
 putPackage :: Package -> Put
-putPackage pack =
-    putWord32le length_prefix    >>
-    putWord8 (packageCmd pack)   >>
-    putWord8 flag_word8          >>
-    putLazyByteString corr_bytes >>
+putPackage pack = do
+    putWord32le length_prefix
+    putWord8 (packageCmd pack)
+    putWord8 flag_word8
+    putLazyByteString corr_bytes
+    for_ cred_m $ \(Credentials login passw) -> do
+        putWord8 $ fromIntegral $ B.length login
+        putByteString login
+        putWord8 $ fromIntegral $ B.length passw
+        putByteString passw
     putByteString pack_data
   where
     pack_data     = packageData pack
-    length_prefix = fromIntegral (B.length pack_data + mandatorySize)
-    flag_word8    = flagWord8 $ packageFlag pack
+    cred_len      = maybe 0 credSize cred_m
+    length_prefix = fromIntegral (B.length pack_data + mandatorySize + cred_len)
+    cred_m        = packageCred pack
+    flag_word8    = maybe 0x00 (const 0x01) cred_m
     corr_bytes    = toByteString $ packageCorrelation pack
+
+--------------------------------------------------------------------------------
+credSize :: Credentials -> Int
+credSize (Credentials login passw) = B.length login + B.length passw + 2
 
 --------------------------------------------------------------------------------
 mandatorySize :: Int
diff --git a/Database/EventStore/Internal/Processor.hs b/Database/EventStore/Internal/Processor.hs
--- a/Database/EventStore/Internal/Processor.hs
+++ b/Database/EventStore/Internal/Processor.hs
@@ -15,6 +15,7 @@
 module Database.EventStore.Internal.Processor
     ( InternalException(..)
     , Processor(..)
+    , DropReason(..)
     , Subscription(..)
     , newProcessor
     ) where
@@ -61,8 +62,8 @@
       }
 
 --------------------------------------------------------------------------------
-newProcessor :: Int -> IO Processor
-newProcessor max_at = sync $ network max_at
+newProcessor :: Settings -> IO Processor
+newProcessor sett = sync $ network sett
 
 --------------------------------------------------------------------------------
 -- Exception
@@ -108,8 +109,8 @@
 heartbeatRequestCmd = 0x01
 
 --------------------------------------------------------------------------------
-network :: Int -> Reactive Processor
-network max_at = do
+network :: Settings -> Reactive Processor
+network sett = do
     (onConnect, pushConnect)         <- newEvent
     (onConnected, pushConnected)     <- newEvent
     (onCleanup, pushCleanup)         <- newEvent
@@ -118,17 +119,18 @@
     (onReceived, pushReceived)       <- newEvent
     (onSend, pushSend)               <- newEvent
 
-    push_new_op <- operationNetwork pushSend
+    push_new_op <- operationNetwork sett
+                                    pushSend
                                     (pushReconnect Reconnect)
                                     onReceived
 
-    push_sub <- subscriptionNetwork pushSend onReceived
+    push_sub <- subscriptionNetwork sett pushSend onReceived
 
     let stateE = fmap connected  onConnected    <>
                  fmap reconnected onReconnected <>
                  fmap received onReceived
 
-    stateB <- accum (initState max_at) stateE
+    stateB <- accum (initState $ s_maxRetries sett) stateE
 
     let heartbeatP pkg = packageCmd pkg == heartbeatRequestCmd
         onlyHeartbeats = filterE heartbeatP onReceived
diff --git a/Database/EventStore/Internal/Reader.hs b/Database/EventStore/Internal/Reader.hs
--- a/Database/EventStore/Internal/Reader.hs
+++ b/Database/EventStore/Internal/Reader.hs
@@ -47,19 +47,24 @@
 getLengthPrefix = fmap fromIntegral getWord32le
 
 --------------------------------------------------------------------------------
+authOffset :: Int
+authOffset = 18
+
+--------------------------------------------------------------------------------
 getPackage :: Get Package
 getPackage = do
     cmd  <- getWord8
     flg  <- getFlag
     col  <- getUUID
+    cred <- getCredentials flg
     rest <- remaining
     dta  <- getBytes rest
 
     let pack = Package
                { packageCmd         = cmd
-               , packageFlag        = flg
                , packageCorrelation = col
                , packageData        = dta
+               , packageCred        = cred
                }
 
     return pack
@@ -72,6 +77,20 @@
         0x00 -> return None
         0x01 -> return Authenticated
         _    -> fail $ printf "TCP: Unhandled flag value 0x%x" wd
+
+--------------------------------------------------------------------------------
+getCredEntryLength :: Get Int
+getCredEntryLength = fmap fromIntegral getWord8
+
+--------------------------------------------------------------------------------
+getCredentials :: Flag -> Get (Maybe Credentials)
+getCredentials None = return Nothing
+getCredentials _ = do
+    loginLen <- getCredEntryLength
+    login    <- getBytes loginLen
+    passwLen <- getCredEntryLength
+    passw    <- getBytes passwLen
+    return $ Just $ credentials login passw
 
 --------------------------------------------------------------------------------
 getUUID :: Get UUID
diff --git a/Database/EventStore/Internal/Types.hs b/Database/EventStore/Internal/Types.hs
--- a/Database/EventStore/Internal/Types.hs
+++ b/Database/EventStore/Internal/Types.hs
@@ -454,14 +454,28 @@
 flagWord8 Authenticated = 0x01
 
 --------------------------------------------------------------------------------
+-- Credentials
+--------------------------------------------------------------------------------
+data Credentials
+    = Credentials
+      { credLogin    :: !ByteString
+      , credPassword :: !ByteString
+      }
+    deriving Show
+
+--------------------------------------------------------------------------------
+credentials :: ByteString -> ByteString -> Credentials
+credentials = Credentials
+
+--------------------------------------------------------------------------------
 -- Package
 --------------------------------------------------------------------------------
 data Package
     = Package
       { packageCmd         :: !Word8
-      , packageFlag        :: !Flag
       , packageCorrelation :: !UUID
       , packageData        :: !ByteString
+      , packageCred        :: !(Maybe Credentials)
       }
     deriving Show
 
@@ -471,17 +485,21 @@
 -- | Global @ConnectionManager@ settings
 data Settings
     = Settings
-      { _heartbeatInterval :: NominalDiffTime
-      , _heartbeatTimeout  :: NominalDiffTime
-      , _requireMaster     :: Bool
+      { s_heartbeatInterval :: NominalDiffTime
+      , s_heartbeatTimeout  :: NominalDiffTime
+      , s_requireMaster     :: Bool
+      , s_credentials       :: Maybe Credentials
+      , s_maxRetries        :: Int
       }
 
 --------------------------------------------------------------------------------
 defaultSettings :: Settings
 defaultSettings = Settings
-                  { _heartbeatInterval = msDiffTime 750  -- 750ms
-                  , _heartbeatTimeout  = msDiffTime 1500 -- 1500ms
-                  , _requireMaster     = True
+                  { s_heartbeatInterval = msDiffTime 750  -- 750ms
+                  , s_heartbeatTimeout  = msDiffTime 1500 -- 1500ms
+                  , s_requireMaster     = True
+                  , s_credentials       = Nothing
+                  , s_maxRetries        = 3
                   }
 
 --------------------------------------------------------------------------------
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -10,13 +10,13 @@
   5. ReadStreamEvents (Forward and Backward)
   6. ReadAllEvents (Forward and Backward)
   7. Volatile subscriptions
+  8. Authentication
 
 TODO
 ====
 
   1. All kind of Subscriptions
-  2. Authentication
-  3. SSL
+  2. SSL
 
 Requirements
 ============
diff --git a/eventstore.cabal b/eventstore.cabal
--- a/eventstore.cabal
+++ b/eventstore.cabal
@@ -10,7 +10,7 @@
 -- PVP summary:      +-+------- breaking API changes
 --                   | | +----- non-breaking API additions
 --                   | | | +--- code changes with no API change
-version:             0.1.1.0
+version:             0.1.2.0
 
 -- A short (one-line) description of the package.
 synopsis: EventStore Haskell TCP Client