diff --git a/include/polarssl/aes.h b/include/polarssl/aes.h
index efc13da..80fd6d9 100644
--- a/include/polarssl/aes.h
+++ b/include/polarssl/aes.h
@@ -111,6 +111,11 @@
 /**
  * \brief          AES-CFB128 buffer encryption/decryption.
  *
+ * Note: Due to the nature of CFB you should use the same key schedule for
+ * both encryption and decryption. So a context initialized with
+ * aes_setkey_enc() for both AES_ENCRYPT and AES_DECRYPT.
+ *
+ * both 
  * \param ctx      AES context
  * \param mode     AES_ENCRYPT or AES_DECRYPT
  * \param length   length of the input data
@@ -134,6 +139,10 @@
  *
  * Warning: You have to keep the maximum use of your counter in mind!
  *
+ * Note: Due to the nature of CTR you should use the same key schedule for
+ * both encryption and decryption. So a context initialized with
+ * aes_setkey_enc() for both AES_ENCRYPT and AES_DECRYPT.
+ *
  * \param length        The length of the data
  * \param nc_off        The offset in the current stream_block (for resuming
  *                      within current cipher stream). The offset pointer to