5 files changed, 13 insertions, 0 deletions
diff --git a/src/block/aes/aes.cpp b/src/block/aes/aes.cpp
index 9fb12cd11..5f47762a8 100644
--- a/src/block/aes/aes.cpp
+++ b/src/block/aes/aes.cpp
@@ -2,6 +2,8 @@
 * AES
 * (C) 1999-2010 Jack Lloyd
 *
+* Based on the public domain reference implemenation
+*
 * Distributed under the terms of the Botan license
 */
 
diff --git a/src/block/des/des.cpp b/src/block/des/des.cpp
index 739dfe87c..c500e9bab 100644
--- a/src/block/des/des.cpp
+++ b/src/block/des/des.cpp
@@ -2,6 +2,9 @@
 * DES
 * (C) 1999-2008 Jack Lloyd
 *
+* Based on a public domain implemenation by Phil Karn (who in turn
+* credited Richard Outerbridge and Jim Gillogly)
+*
 * Distributed under the terms of the Botan license
 */
 
diff --git a/src/block/serpent/serpent.cpp b/src/block/serpent/serpent.cpp
index 1d940cf39..b3cf0f6c9 100644
--- a/src/block/serpent/serpent.cpp
+++ b/src/block/serpent/serpent.cpp
@@ -2,6 +2,9 @@
 * Serpent
 * (C) 1999-2007 Jack Lloyd
 *
+* The sbox expressions used here were discovered by Dag Arne Osvik and
+* are described in his paper "Speeding Up Serpent".
+*
 * Distributed under the terms of the Botan license
 */
 
diff --git a/src/block/square/square.cpp b/src/block/square/square.cpp
index b1517b990..cd1865582 100644
--- a/src/block/square/square.cpp
+++ b/src/block/square/square.cpp
@@ -2,6 +2,8 @@
 * Square
 * (C) 1999-2007 Jack Lloyd
 *
+* Based on the public domain reference implemenation
+*
 * Distributed under the terms of the Botan license
 */
 
diff --git a/src/block/twofish/twofish.cpp b/src/block/twofish/twofish.cpp
index 41bc7ca1c..c0735e202 100644
--- a/src/block/twofish/twofish.cpp
+++ b/src/block/twofish/twofish.cpp
@@ -2,6 +2,9 @@
 * Twofish
 * (C) 1999-2007 Jack Lloyd
 *
+* The key schedule implemenation is based on a public domain
+* implementation by Matthew Skala
+*
 * Distributed under the terms of the Botan license
 */