From 7c1ee9ce876a3ee4e6dbafd783f68c59ad650604 Mon Sep 17 00:00:00 2001
From: akwizgran <akwizgran@users.sourceforge.net>
Date: Thu, 31 Dec 2015 17:46:18 +0000
Subject: [PATCH] Restored accidentally deleted javadoc.

---
 briar-core/src/org/briarproject/crypto/DoubleDigest.java | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/briar-core/src/org/briarproject/crypto/DoubleDigest.java b/briar-core/src/org/briarproject/crypto/DoubleDigest.java
index a8670a217..1d1fdd99d 100644
--- a/briar-core/src/org/briarproject/crypto/DoubleDigest.java
+++ b/briar-core/src/org/briarproject/crypto/DoubleDigest.java
@@ -3,6 +3,15 @@ package org.briarproject.crypto;
 import org.briarproject.api.crypto.MessageDigest;
 import org.spongycastle.crypto.Digest;
 
+/**
+ * A message digest that prevents length extension attacks - see Ferguson and
+ * Schneier, <i>Practical Cryptography</i>, chapter 6.
+ * <p>
+ * "Let h be an interative hash function. The hash function h<sub>d</sub> is
+ * defined by h<sub>d</sub> := h(h(m)), and has a claimed security level of
+ * min(k, n/2) where k is the security level of h and n is the size of the hash
+ * result."
+ */
 class DoubleDigest implements MessageDigest {
 
 	private final Digest delegate;