phc-discussions - Re: [PHC] Argon2 using memset still

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Message-ID: <CAJm83bBHV+EeQiuZmn6wv+CSOJdDGG9GWZdPyybD7kjJFwi22g@mail.gmail.com>
Date: Thu, 27 Aug 2015 12:43:33 -0400
From: Daniel Franke <dfoxfranke@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Argon2 using memset still

On 8/27/15, Bill Cox <waywardgeek@...il.com> wrote:
> g++ has a habit of optimizing calls to memset away.  I doubt that Argon2
> succeed in it's attempts to clear memory.  I copied this function from
> Blake2:
>
> /* prevents compiler optimizing out memset() */
> static inline void secure_zero_memory( void *v, size_t n )
> {
>   volatile uint8_t *p = ( volatile uint8_t * )v;
>   while( n-- ) *p++ = 0;
> }

This is an improvement over memset, but note the comment above
secure_wipe() in
https://github.com/dfoxfranke/earworm/blob/master/util-ref.h.