diff --git a/include/crypto/ctr.h b/include/crypto/ctr.h
new file mode 100644
index 0000000..4180fc0
--- /dev/null
+++ b/include/crypto/ctr.h
@@ -0,0 +1,20 @@
+/*
+ * CTR: Counter mode
+ *
+ * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ */
+
+#ifndef _CRYPTO_CTR_H
+#define _CRYPTO_CTR_H
+
+#define CTR_RFC3686_NONCE_SIZE 4
+#define CTR_RFC3686_IV_SIZE 8
+#define CTR_RFC3686_BLOCK_SIZE 16
+
+#endif  /* _CRYPTO_CTR_H */