commit a9a5ff5f313a4832227de50f0cd21268cf415bc6
author Andrzej Kurek <andrzej.kurek@arm.com> Wed Jul 15 08:50:59 2020 -0400
committer Andrzej Kurek <andrzej.kurek@arm.com> Fri Jul 17 03:28:32 2020 -0400
tree f67a0fcd854b3424beec117fd0e7809733a0a767
parent 11ddf25828adce96dc7a9cf259b34a19f912f190

aes: add a comment about expected keybits value.

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>

library/aes.c

diff --git a/library/aes.c b/library/aes.c
index c4710c4..e9e7544 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -725,6 +725,8 @@
         return( mbedtls_aesni_setkey_enc( (unsigned char *) ctx->rk, key, keybits ) );
 #endif
 
+    /* Three least significant bits are truncated from keybits, which is
+     * expected to be a multiple of 8. */
     mbedtls_platform_memset( RK, 0, keybits >> 3 );
     offset = mbedtls_platform_random_in_range( keybits >> 5 );