aes: add a comment about expected keybits value.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
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 );