commit b06ec05dc0258788e6e03528e3d1b0fe1981a220
author Piotr Nowicki <piotr.nowicki@arm.com> Wed Jun 03 15:59:59 2020 +0200
committer Piotr Nowicki <piotr.nowicki@arm.com> Mon Jun 08 14:21:38 2020 +0200
tree a623034e62c062c881c97d83f2ca3b5ad3cad601
parent 478b05c34ccc5cebe1019409b61cb42da300d8ba

Add comment for mbedtls_platform_random_delay()

Signed-off-by: Piotr Nowicki <piotr.nowicki@arm.com>

library/platform_util.c

diff --git a/library/platform_util.c b/library/platform_util.c
index 3869f30..19958fa 100644
--- a/library/platform_util.c
+++ b/library/platform_util.c
@@ -190,6 +190,9 @@
     do
     {
         i++;
+        /* Dummy calculations to increase the time between iterations and
+         * make side channel attack more difficult by reducing predictability
+         * of its behaviour */
         shift = rn_2 & 0x07;
         if ( i % 2 )
             rn_2 = (uint32_t)( rn_2 >> shift | rn_2 << ( 32 - shift ) );