Added some descriptions of functions
Signed-off-by: Piotr Nowicki <piotr.nowicki@arm.com>
diff --git a/library/platform_util.c b/library/platform_util.c
index 2b8eb56..3869f30 100644
--- a/library/platform_util.c
+++ b/library/platform_util.c
@@ -111,6 +111,9 @@
/* Randomize initial data to prevent leakage while copying */
uint32_t data = mbedtls_platform_random_in_range( 256 );
+ /* Use memset with random value at first to increase security - memset is
+ not normally part of the memcpy function and here can be useed
+ with regular, unsecured implementation */
memset( (void *) dst, data, num );
memcpy( (void *) ( (unsigned char *) dst + start_offset ),
(void *) ( (unsigned char *) src + start_offset ),
@@ -124,8 +127,8 @@
volatile const unsigned char *B = (volatile const unsigned char *) buf2;
volatile unsigned char diff = 0;
- size_t i = num;
- size_t flow_counter = 0;
+ /* Start from a random location and check the correct number of iterations */
+ size_t i, flow_counter = 0;
size_t start_offset = (size_t) mbedtls_platform_random_in_range( num );
for( i = start_offset; i < num; i++ )
diff --git a/tinycrypt/ecc.c b/tinycrypt/ecc.c
index 8f2cf0e..ba36267 100644
--- a/tinycrypt/ecc.c
+++ b/tinycrypt/ecc.c
@@ -290,6 +290,7 @@
uECC_word_t tmp1, tmp2;
volatile int i;
+ /* Start from a random location and check the correct number of iterations */
int start_offset = mbedtls_platform_random_in_range(NUM_ECC_WORDS);
for (i = start_offset; i < NUM_ECC_WORDS; ++i) {
@@ -306,6 +307,7 @@
diff |= (tmp1 ^ tmp2);
}
+ /* Random delay to increase security */
mbedtls_platform_random_delay();
/* Return 0 only when diff is 0 and flow_counter is equal to NUM_ECC_WORDS */