diff --git a/Crypto/PasswordStore.hs b/Crypto/PasswordStore.hs
--- a/Crypto/PasswordStore.hs
+++ b/Crypto/PasswordStore.hs
@@ -103,6 +103,7 @@
   ) where
 
 
+import qualified Crypto.Hash as CH
 import qualified Crypto.Hash.SHA256 as H
 import qualified Data.ByteString.Char8 as B
 import qualified Data.ByteString as BS
@@ -110,8 +111,8 @@
 import qualified Data.Binary as Binary
 import Control.Monad
 import Control.Monad.ST
+import Data.Byteable (toBytes)
 import Data.STRef
-import qualified Data.Digest.Pure.SHA as SHA
 import Data.Bits
 import Data.ByteString.Char8 (ByteString)
 import Data.ByteString.Base64 (encode, decodeLenient)
@@ -119,6 +120,9 @@
 import System.Random
 import Data.Maybe
 import qualified Control.Exception
+import Data.Char
+import Data.List
+import Data.Function
 
 ---------------------
 -- Cryptographic base
@@ -150,8 +154,7 @@
            -> ByteString
            -- ^ The encoded message
 hmacSHA256 secret msg =
-  let digest = SHA.hmacSha256 (fromStrict secret) (fromStrict msg)
-    in toStrict . SHA.bytestringDigest $ digest
+    toBytes (CH.hmacGetDigest (CH.hmac secret msg) :: CH.Digest CH.SHA256)
 
 -- | PBKDF2 key-derivation function.
 -- For details see @http://tools.ietf.org/html/rfc2898@.
@@ -296,6 +299,12 @@
 makePasswordSalt :: ByteString -> Salt -> Int -> ByteString
 makePasswordSalt = makePasswordSaltWith pbkdf1 (2^)
 
+-- | Constant-time comparison function to use instead of == when comparing with a secret
+constantTimeCompare a b = 
+  ((==) `on` length) a b && 0 == (foldl1 (.|.) joined)
+  where
+    joined = zipWith (xor `on` ord) a b
+
 -- | 'verifyPasswordWith' @algorithm userInput pwHash@ verifies
 -- the password @userInput@ given by the user against the stored password
 -- hash @pwHash@, with the hashing algorithm @algorithm@.  Returns 'True' if the
@@ -322,7 +331,7 @@
     case readPwHash pwHash of
       Nothing -> False
       Just (strength, salt, goodHash) ->
-          encode (algorithm userInput salt (strengthModifier strength)) == goodHash
+          encode (algorithm userInput salt (strengthModifier strength)) `constantTimeCompare` goodHash
 
 -- | Like 'verifyPasswordWith', but uses 'pbkdf1' as algorithm.
 verifyPassword :: ByteString -> ByteString -> Bool
diff --git a/pwstore-fast.cabal b/pwstore-fast.cabal
--- a/pwstore-fast.cabal
+++ b/pwstore-fast.cabal
@@ -1,5 +1,5 @@
 Name:                pwstore-fast
-Version:             2.4.1
+Version:             2.4.2
 Synopsis:            Secure password storage.
 Description:         To store passwords securely, they should be salted,
                      then hashed with a slow hash function. This library
@@ -30,7 +30,7 @@
   Build-depends:   base >= 4, base < 5, bytestring >= 0.9,
                    base64-bytestring >= 0.1,
                    binary >= 0.5,
-                   SHA >= 1.6.1,
-                   cryptohash >= 0.6, random >= 1
+                   cryptohash >= 0.6, random >= 1,
+                   byteable >= 0.1
   ghc-options:     -Wall