Explain the purpose of check_parity

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2020-08-26 10:24:26 +02:00
parent 34f063ca47
commit 6c75152b9f

View file

@ -57,6 +57,16 @@
TEST_ASSERT( PSA_##flag( alg ) == !! ( ( flags ) & flag ) )
/* Check the parity of value.
*
* There are several numerical encodings for which the PSA Cryptography API
* specification deliberately defines encodings that all have the same
* parity. This way, a data glitch that flips one bit in the data cannot
* possibly turn a valid encoding into another valid encoding. Here in
* the tests, we check that the values (including Mbed TLS vendor-specific
* values) have the expected parity.
*
* The expected parity is even so that 0 is considered a valid encoding.
*
* Return 0 if value has even parity and a nonzero value otherwise. */
int check_parity( uint32_t value )
{