Improve documentation of CBC functions
diff --git a/include/polarssl/des.h b/include/polarssl/des.h
index 86e6b1d..998ae46 100644
--- a/include/polarssl/des.h
+++ b/include/polarssl/des.h
@@ -214,6 +214,14 @@
/**
* \brief DES-CBC buffer encryption/decryption
*
+ * \note Upon exit, the content of the IV is updated so that you can
+ * call the function same function again on the following
+ * block(s) of data and get the same result as if it was
+ * encrypted in one call. This allows a "streaming" usage.
+ * If on the other hand you need to retain the contents of the
+ * IV, you should either save it manually or use the cipher
+ * module instead.
+ *
* \param ctx DES context
* \param mode DES_ENCRYPT or DES_DECRYPT
* \param length length of the input data
@@ -246,6 +254,14 @@
/**
* \brief 3DES-CBC buffer encryption/decryption
*
+ * \note Upon exit, the content of the IV is updated so that you can
+ * call the function same function again on the following
+ * block(s) of data and get the same result as if it was
+ * encrypted in one call. This allows a "streaming" usage.
+ * If on the other hand you need to retain the contents of the
+ * IV, you should either save it manually or use the cipher
+ * module instead.
+ *
* \param ctx 3DES context
* \param mode DES_ENCRYPT or DES_DECRYPT
* \param length length of the input data