Implement HMAC support in lib/crypto.

lib/crypto/crypto.dart

Index: lib/crypto/crypto.dart
diff --git a/lib/crypto/crypto.dart b/lib/crypto/crypto.dart
index 6a839974017206c69f7f1bc73cea24a0209bca80..6b2c9f32d86779d1c75b43ccd6536d2eed06d6db 100644
--- a/lib/crypto/crypto.dart
+++ b/lib/crypto/crypto.dart
@@ -4,6 +4,7 @@
 
 #library('crypto');
 
+#source('hmac.dart');
 #source('sha_utils.dart');
 #source('sha1.dart');
 #source('sha256.dart');
@@ -12,10 +13,14 @@
  * 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. Once the [digest] method has been
- * called the CryptoHash object is in an invalid state and should not be
- * used again. If [digest] or [update] are called after the first call to
- * [digest] a CryptoHashException is thrown.
+ * is used to extract the message digest.
+ *
+ * Once the [digest] method has been called the CryptoHash object is in an
+ * invalid state and should not be used again. If [digest] or [update] are
+ * called after the first call to [digest] a CryptoHashException is thrown.

[Ben Laurie (Google), 2012/04/27 13:26:33]

I still say you should be able to call [digest] a second time.

[Mads Ager (google), 2012/04/30 07:56:57]

OK, allowed multiple calls to digest to extract the message digest.

+ *
+ * If multiple instances of a given CryptoHash is needed the [newInstance]
+ * method can provide a new instance.
  */
 interface CryptoHash {
   /**
@@ -28,6 +33,16 @@ interface CryptoHash {
    * a list of bytes.
    */
   List<int> digest();
+
+  /**
+   * Returns a new instance of this hash function.
+   */
+  CryptoHash newInstance();
+
+  /**
+   * Block size of the hash in bytes.
+   */
+  int get blockSize();
 }
 
 /**
@@ -46,6 +61,31 @@ interface SHA256 extends CryptoHash default _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 {

[Ben Laurie (Google), 2012/04/27 13:26:33]

Why CryptoHash and not CryptoHMAC?

[Mads Ager (google), 2012/04/30 07:56:57]

Yeah, good question. There is next to zero chance that HMAC will conflict with
anything else. I guess these should really by Hash and HMAC. Changed. If this
leads to issues with conflicts we can rename.

+  /**
+   * Create an [HMAC] object from a [CryptoHash] and a key.
+   */
+  HMAC(CryptoHash 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();
+}
+
+
+/**
  * CryptoHashExceptions are thrown on invalid use of a CryptoHash
  * object.
  */