Add documentation for change in CMAC self-test behaviour
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
diff --git a/ChangeLog.d/allow_alt_cmac_without_des.txt b/ChangeLog.d/allow_alt_cmac_without_des.txt
new file mode 100644
index 0000000..5193a9e
--- /dev/null
+++ b/ChangeLog.d/allow_alt_cmac_without_des.txt
@@ -0,0 +1,3 @@
+Changes
+ * Alternative implementations of CMAC may now opt to not support 3DES as a
+ CMAC block cipher, and still pass the CMAC self test.
diff --git a/include/mbedtls/cmac.h b/include/mbedtls/cmac.h
index cb538d0..b67305c 100644
--- a/include/mbedtls/cmac.h
+++ b/include/mbedtls/cmac.h
@@ -198,6 +198,13 @@
/**
* \brief The CMAC checkup routine.
*
+ * \note In case the CMAC routines are provided by an alternative
+ * implementation (i.e. #MBEDTLS_CMAC_ALT is defined), the
+ * checkup routine will succeed even if the implementation does
+ * not support the less widely used AES-192 or 3DES primitives.
+ * The self-test requires at least AES-128 and AES-256 to be
+ * supported by the underlying implementation.
+ *
* \return \c 0 on success.
* \return \c 1 on failure.
*/
