diff --git a/README.ja.md b/README.ja.md
index e78c88c..6312499 100644
--- a/README.ja.md
+++ b/README.ja.md
@@ -35,12 +35,6 @@ Play2.2.1 で動作確認をしています。
 柔軟に他の操作を組み合わせて使用することができます。
 
 
-以前のバージョン
----------------------------------------
-
-Play2.1.x 向けの使用方法は [0.10.1 README](https://github.com/t2v/play2-auth/blob/release0.10.1/README.ja.md)をご参照ください。
-Play2.0.x 向けの使用方法は [0.7 README](https://github.com/t2v/play2-auth/blob/release0.7/README.ja.md)をご参照ください。
-
 Play2.1以前をお使いの方へ
 ---------------------------------------
 
@@ -53,15 +47,15 @@ Play2.1以前をお使いの方へ
 
 `Build.scala` もしくは `build.sbt` にライブラリ依存性定義を追加します。
 
-        "jp.t2v" %% "play2-auth"      % "0.11.0",
-        "jp.t2v" %% "play2-auth-test" % "0.11.0" % "test"
+        "jp.t2v" %% "play2-auth"      % "0.11.1",
+        "jp.t2v" %% "play2-auth-test" % "0.11.1" % "test"
 
 For example: `Build.scala`
 
 ```scala
   val appDependencies = Seq(
-    "jp.t2v" %% "play2-auth"      % "0.11.0-SNAPSHT",
-    "jp.t2v" %% "play2-auth-test" % "0.11.0-SNAPSHT" % "test"
+    "jp.t2v" %% "play2-auth"      % "0.11.1",
+    "jp.t2v" %% "play2-auth-test" % "0.11.1" % "test"
   )
 ```
 
diff --git a/README.md b/README.md
index f7c1386..93e0ac9 100644
--- a/README.md
+++ b/README.md
@@ -34,14 +34,6 @@ Play2x-Auth provides an interface that returns an [`Either[PlainResult, User]`](
 making writing complicated action methods easier.   [`Either`](http://www.scala-lang.org/api/current/scala/util/Either.html) is a wrapper similar to `Option`
 
 
-Previous Version
----------------------------------------
-
-for Play2.1.x, Please see [previous version 0.10.1 README](https://github.com/t2v/play2-auth/tree/release0.10.1)
-
-for Play2.0.x, Please see [previous version 0.7 README](https://github.com/t2v/play2-auth/tree/release0.7)
-
-
 Attention
 ---------------------------------------
 
@@ -55,15 +47,15 @@ Add dependency declarations into your `Build.scala` or `build.sbt` file:
 
 * __for Play2.2.x__
 
-        "jp.t2v" %% "play2-auth"      % "0.11.0",
-        "jp.t2v" %% "play2-auth-test" % "0.11.0" % "test"
+        "jp.t2v" %% "play2-auth"      % "0.11.1",
+        "jp.t2v" %% "play2-auth-test" % "0.11.1" % "test"
 
 For example your `Build.scala` might look like this:
 
 ```scala
   val appDependencies = Seq(
-    "jp.t2v" %% "play2-auth"      % "0.11.0",
-    "jp.t2v" %% "play2-auth.test" % "0.11.0" % "test"
+    "jp.t2v" %% "play2-auth"      % "0.11.1",
+    "jp.t2v" %% "play2-auth.test" % "0.11.1" % "test"
   )
 ```
 
diff --git a/module/src/main/scala/jp/t2v/lab/play2/auth/CookieUtil.scala b/module/src/main/scala/jp/t2v/lab/play2/auth/CookieUtil.scala
index 1d03ec2..4086bbb 100644
--- a/module/src/main/scala/jp/t2v/lab/play2/auth/CookieUtil.scala
+++ b/module/src/main/scala/jp/t2v/lab/play2/auth/CookieUtil.scala
@@ -8,7 +8,22 @@ trait CookieUtil {
 
   def verifyHmac(cookie: Cookie): Option[String] = {
     val (hmac, value) = cookie.value.splitAt(40)
-    if (Crypto.sign(value) == hmac) Some(value) else None
+    if (safeEquals(Crypto.sign(value), hmac)) Some(value) else None
+  }
+
+  // Do not change this unless you understand the security issues behind timing attacks.
+  // This method intentionally runs in constant time if the two strings have the same length.
+  // If it didn't, it would be vulnerable to a timing attack.
+  protected def safeEquals(a: String, b: String) = {
+    if (a.length != b.length) {
+      false
+    } else {
+      var equal = 0
+      for (i <- Array.range(0, a.length)) {
+        equal |= a(i) ^ b(i)
+      }
+      equal == 0
+    }
   }
 
 }
diff --git a/project/Build.scala b/project/Build.scala
index ae9ac1f..8c0e4e3 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -9,7 +9,7 @@ object ApplicationBuild extends Build {
   val playVersion = "2.2.0"
 
   lazy val baseSettings = Seq(
-    version            := "0.11.0",
+    version            := "0.11.1",
     scalaVersion       := "2.10.3",
     scalaBinaryVersion := "2.10",
     organization       := "jp.t2v",