add Crypto.sign functions

framework/play/src/main/scala/play/api/libs/Codec.scala

@@ -27,4 +27,25 @@ object Codec {
    */
   def sha1(text: String): String = sha1(text.getBytes)
 
+  private val hexChars = Array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f')
+
+  /**
+   * Converts a byte array into an array of char denoting a hexadecimal representation
+   */
+  def toHex(array: Array[Byte]): Array[Char] = {
+    val result = new Array[Char](array.length * 2)
+    for (i <- 0 until array.length) {
+      val b = array(i) & 0xff
+      result(2 * i) = hexChars(b >> 4)
+      result(2 * i + 1) = hexChars(b & 0xf)
+    }
+    result
+  }
+
+  /**
+   * Converts a byte array into a String denoting a hexadecimal representation
+   */
+  def toHexString(array: Array[Byte]): String = {
+    new String(toHex(array))
+  }
 }

framework/play/src/main/scala/play/api/libs/Crypto.scala

@@ -0,0 +1,24 @@
+package play.api.libs
+
+import java.security._
+import javax.crypto._
+import javax.crypto.spec.SecretKeySpec
+
+import play.api.Play
+import play.api.PlayException
+import play.api.Configuration.Config
+
+object Crypto {
+  def sign(message: String, key: Array[Byte]): String = {
+    val mac = Mac.getInstance("HmacSHA1")
+    mac.init(new SecretKeySpec(key, "HmacSHA1"))
+    Codec.toHexString(mac.doFinal(message.getBytes("utf-8")))
+  }
+
+  def sign(message: String): String = {
+    Play.maybeApplication.get.configuration.get("application.secret") match {
+      case Some(Config(key, value, file)) => sign(message, value.getBytes)
+      case _ => throw PlayException("Configuration error", "Missing application.secret")
+    }
+  }
+}