Add CryptoUtils class.

lib/crypto/crypto.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #library('crypto');
 
+#source('crypto_utils.dart');
 #source('hmac.dart');
 #source('sha_utils.dart');
 #source('sha1.dart');
 #source('sha256.dart');
 
 /**
  * Interface for cryptographic hash functions.
  *
  * The [update] method is used to add data to the hash. The [digest] method
  * is used to extract the message digest.
@@ skipping 35 matching lines @@
   SHA1();
 }
 
 /**
  * SHA256 hash function implementation.
  */
 interface SHA256 extends Hash default _SHA256 {
   SHA256();
 }
 
-
 /**
  * Hash-based Message Authentication Code support.
  *
  * The [update] method is used to add data to the message. The [digest] method
  * is used to extract the message authentication code.
  */
 interface HMAC default _HMAC {
   /**
    * Create an [HMAC] object from a [Hash] and a key.
    */
   HMAC(Hash hash, List<int> key);
 
   /**
    * Add a list of bytes to the message.
    */
   HMAC update(List<int> data);
 
   /**
    * Perform the actual computation and extract the message digest
    * as a list of bytes.
    */
   List<int> digest();
 }
 
+/**
+ * Utility methods for working with message digests.
+ */
+class CryptoUtils {
+  /**
+   * Convert a message digest which is a list of bytes into a hex
+   * string.
+   */
+  static String digestToHex(List<int> digest) {

[Søren Gjesse, 2012/05/07 14:26:34]

Shouldn't this just be bytesToHex? This can be used for more than just digests.
For crypto input can also be for instance keys.

[Mads Ager (google), 2012/05/07 14:34:59]

Good point. Done.

+    return _CryptoUtils.digestToHex(digest);
+  }
+}
 
 /**
  * HashExceptions are thrown on invalid use of a Hash
  * object.
  */
 class HashException {
   HashException(String this.message);
   toString() => "HashException: $message";
   String message;
 }