2017-06-11 22:48 GMT+02:00 Emmanuel Grumbach <egrumbach@xxxxxxxxx>: > On Sun, Jun 11, 2017 at 4:36 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: >> >> On Sun, Jun 11, 2017 at 1:13 AM, Kalle Valo <kvalo@xxxxxxxxxxxxxx> wrote: >> > "Jason A. Donenfeld" <Jason@xxxxxxxxx> writes: >> > >> >> Whenever you're comparing two MACs, it's important to do this using >> >> crypto_memneq instead of memcmp. With memcmp, you leak timing information, >> >> which could then be used to iteratively forge a MAC. >> > >> > Do you have any pointers where I could learn more about this? >> >> While not using C specifically, this talks about the problem generally: >> https://www.chosenplaintext.ca/articles/beginners-guide-constant-time-cryptography.html >> > > Sorry for the stupid question, but the MAC address is in plaintext in > the air anyway or easily accessible via user space tools. I fail to > see what it is so secret about a MAC address in that code where that > same MAC address is accessible via myriads of ways. I think you're mixing up Media Access Control (MAC) addresses with Message Authentication Code (MAC). The second one is a cryptographic signature of a message.
